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TECHNICAL MANUAL

 RF POWER AMPLIFIER

MODELS 51-S21F-64 and 51-S22F-42

This manual is the property of and contains information which is proprietary to ETO. Reproduction in whole or inpart is prohibited. Neither the manual nor anyinformation contained herein shall be disclosed to anyoneoutside the Company without advance writtenauthorization.

CONTENTS COPYRIGHTED BY

ETO, INC.

4975 NORTH 30th STREET

COLORADO SPRINGS, COLORADO 80919

UNITED STATES OF AMERICA 

June 6, 1997

ETO Part No. ZMX-X160REVISION (A) June 6, 1997

*****************************************************************

AMPLIFIER SERIAL NUMBER: _____________________ 

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PREFACE

GENERAL:

The Models 51-S21F-64 and 51-S22F-42 amplifiers are linear,pulsed, RF power amplifier intended for use as part of a Magnetic

Resonance Imaging System.

The Models 51-S21F-64 and 51-S22F-42 amplifiers are Class 1ordinary equipment without applied parts. They are to be used inan area where there are no flammable anesthetics or gasses used.

The Models 51-S21F-64 and 51-S22F-42 amplifiers are UL Listedunder UL 1012 (file #E95768, 91WC) and are certified by TUV forcompliance with the International Electrotechnical CommissionStandard for Medical Electrical Equipment, IEC 601-1(cert#T9371601-01 & T9371601-02).

The amplifiers do not comply with EMC until the unit is installedinto the MRI system. Verification of EMC requirements must bedone after the installation of the system.

The amplifiers must be enclosed in an outer cabinet when operatedin patient vicinity.

SAFETY:

The 51-S2#F-XX amplifiers must be installed, operated, andserviced by qualified personnel.

The Model 51-S21F-64 amplifier is capable of delivering in excessof 25,000 watts peak of RF power at 64.05 MHz, into a 50 ohm load. This level of RF power can cause severe RF burns and otherinjuries if misused. Never operate the amplifier without havingthe RF output properly terminated into a load capable of handlingthis level of RF power.

The Model 51-S22F-42 amplifiers are capable of delivering inexcess of 10,000 watts peak of RF power at 42.30 MHz, into a 50ohm load. This level of RF power can cause severe RF burns andother injuries if misused. Never operate the amplifier withouthaving the RF output properly terminated into a load capable ofhandling this level of RF power.

The user accepts full responsibility for the proper use of thisamplifier and for all safety issues concerning the use of RFpower for medical purposes.

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 WARNINGS:

LETHAL VOLTAGES ARE PRESENT INSIDE THE AMPLIFIER. DO NOT OPERATETHE AMPLIFIER WITH THE COVERS REMOVED. CONSULT THIS SERVICEMANUAL BEFORE SERVICING THE AMPLIFIER.

DO NOT PLACE HEAVY OBJECTS OR LIQUIDS ON TOP OF THE AMPLIFIER.

DO NOT BLOCK AMPLIFIER INPUT OR EXHAUST VENTREFER TO SECTION 3.2 FOR ADDITIONAL SAFETY REFERENCES. SAFETYSTATEMENTS ARE ALSO PROVIDED IN APPROPRIATE AREAS THROUGHOUTTHIS MANUAL.

ETO, INC. is not responsible for proper or improper installation, application, or

use, nor for patient safety, when this amplifier is used in a Magnetic ResonanceImaging or other system.

ETO will make available on request circuit diagrams, componentpart lists, descriptions, calibration instructions, and otherinformation necessary in the replacement of field replaceableunits (FRU).

The RF Amplifier system has a serial number label attached tothe rear of the amplifier.

This label contains the following information:

Model Number: 51-S21a-bb where a = revision  bb = frequency

Serial Number: Fyyww### where yy = year produced  ww = week produced  ### = sequence number

Part Number: Customers part number Amplifier Class: Class 1Frequency: RF operating frequency

Max RF Output: Maximum pulsed outputMaximum average outputETO mailing address: Address for informationCountry of origin: Made in USA  UL registration marking: Product is UL listedCompliance to IEC 601-1: Product complies with IEC

601-1

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PREFACE (continued)

 MARKINGS ON THE AMPLIFIER:

Dangerous Voltage

Alternating Current

Three-phase alternating current

Earth (Ground: Functional)

Protective Earth (Ground)

Equipotentiality

Attention, consult accompanying documents

Off (power: disconnection from the mains)

On (power: connection to the mains)

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SPECIFICATIONS

MAXIMUM RF POWER OUTPUT: 51-S21F-64 (Mode High)25 KW peak (3 ms rectangular pulse, 5% duty cycle).

  51-S22F-42 (Mode High)

15 KW peak (3 ms rectangular pulse, 5% duty cycle).

MAXIMUM PULSE ENERGY: 51-S21F-64 (Mode High)

  80 Joules in any single pulse  51-S22F-42 (Mode High)

  40 Joules in any single pulse

FREQUENCY OF OPERATION: 51-S21F-6464.05 MHz

  51-S22F-42

42.30 MHz

LINEARITY: +/- 1 dB from full output to a level 40  dB below full output

PULSE VARIATION: Less than 0.5 dB across a 3 ms rectangular   pulse (5% duty cycle, 15 KW output)

INSTANTANEOUS BANDWIDTH: +/- 50 KHz or better at +/- 0.2 dB;

LOAD IMPEDANCE :  Nominal 50 Ohms, unbalanced

DRIVE POWER REQUIREMENTS:  -2dBm to +3 dBm for 15 KW output.  Input VSWR < 1.25:1

HARMONIC OUTPUT :  < -25 dBc

NOISE OUTPUT : < -150 dBm/Hz when gated "OFF"  < -60 dBm/Hz when gated "ON"

GATING: Max. time to meet Specs: < 100 usec "ON"  < 20 usec "OFF"

  Any single gated-on period shall not exceed 20 ms.

  The gating duty cycle shall not exceed 50%. 

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PRIMARY POWER :  208 VAC, +/- 10%, 1 Phase, 50/60 Hz,  30 Amps maximum. (60 Hz factory default)

ENVIRONMENTAL: 

- Temperature: Operating, +10 to +40 degrees C.  Non-Operating, -35 to +60 degrees C.

  - Altitude: Operating, to 10,000 feet ASL.  Non-Operating, to 40,000 feet ASL.

  - Humidity: Operating, to 70% non-condensing.  Non-Operating, to 95% non-condensing.

  - Air Pressure Operating, 70 - 100 kPa

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TABLE OF CONTENTS

1.0 OVERVIEW OF AMPLIFIER ORGANIZATION AND OPERATION ........... ............. .............11.1 GENERAL .......................... ............. ............ ............. ............. ............ .............11.2 FUNCTIONAL BLOCK DIAGRAM ... ............ ............. ............. ............ ............. .............11.2.1 Amplifier Controller ........... ............. ............ ............. ............. ............ ............. .............11.2.2 RF Amplifier Deck ............. ............. ............ ............. ............. ............ ............. .............11.2.3 Low Voltage Power Supply

............ ............ ............. ............. ............ ............. .............2

1.2.4 High Voltage Power Supply ........... ............ ............. ............. ............ ............. .............21.2.5 Ferro-Resonant Supplies . ............. ............ ............. ............. ............ ............. .............21.3 MODES OF AMPLIFIER OPERATION ....... ............. ............. ............ ............. .............21.3.1 MODE "HIGH (BODY)" .... ............. ............ ............. ............. ............ ............. .............31.3.2 MODE "MID (A-5)" ........... ............. ............ ............. ............. ............ ............. .............31.3.3 MODE "LOW (A-1)" (not specified) ............ ............. ............. ............ ............. .............31.4 AMPLIFIER OPERATION, GENERAL ........ ............. ............. ............ ............. .............3

2.0 AMPLIFIER CONTROL ............. ............. ............ ............. ............. ............ ............. .............52.3.1 OVERVIEW ...................... ............. ............ ............. ............. ............ ............. .............52.3.2 CUSTOMER INTERFACE BOARD ........... ............. ............. ............ ............. .............52.3.3 LED DISPLAY BOARD

.... ............. ............ ............. ............. ............ ............. .............5

2.3.4 AMPLIFIER CONTROLLER BOARD ......... ............. ............. ............ ............. .............62.3.4.1 CONTROL PROCESSOR SECTION ..... ............. ............. ............ ............. .............62.3.4.2 CONTROL INTERFACE SECTION ........ ............. ............. ............ ............. .............82.3.4.3 ANALOG INPUT/OUTPUT SECTION ... ............. ............. ............ ............. .............92.3.4.4 DIGITAL INPUT/OUTPUT SECTION ..... ............. ............. ............ ............. .............102.3.5 PA CONTROL BOARD .... ............. ............ ............. ............. ............ ............. .............10

3.0 CONTROL and COMMUNICATIONS .... ............ ............. ............. ............ ............. .............123.1 RS-232 SERIAL INTERFACE ........... ............ ............. ............. ............ ............. .............123.2 COMMAND FORMAT ......... ............. ............ ............. ............. ............ ............. .............123.2.1 The OPER=< OFF | STBY | ON | ? > Command ..... ............. ............ ............. .............133.2.2 The MODE= < SSA | LOW | MID | HIGH | HEAD | BODY | ? > Command

.... .............14

3.2.3 The FREQ= dd.dd or ? Command ............ ............. ............. ............ ............. .............143.2.4 The AFT=< ON | OFF | ? > Command ...... ............. ............. ............ ............. .............153.2.5 The PWR= hhh or ? Command ... ............ ............. ............. ............ ............. .............153.2.6 The FPWR= ? Command ............ ............ ............. ............. ............ ............. .............173.2.7 The FAULT= < ? | 0 - 10 | CLEAR > Command ..... ............. ............ ............. .............173.2.8 The WARN= < ? | 0 - 10 | CLEAR > Command ..... ............. ............ ............. .............173.2.9 HOURS=< ? | AMP | PA | IPA | CLR PA | CLR IPA >........... ............ ............. .............183.2.10 TEST= < ON | OFF | TUBES | PA TUBE | IPA TUBE

RF | SSA RF | PA RF | AMP RF > ......... ............. ............. ............ ............. .............193.2.10.1 DC TUBE TEST DESCRIPTION ........... ............. ............. ............ ............. .............193.2.10.2 RF TESTS DESCRIPTION

........ ............ ............. ............. ............ ............. .............19

3.2.10.3 TEST COMMAND USE ............ ............ ............. ............. ............ ............. .............203.2.11 TUBE= ? ......................... ............. ............ ............. ............. ............ ............. .............213.2.12 ATEST= < ON | OFF | ? > .......... ............ ............. ............. ............ ............. .............213.2.13. MESSAGES FROM THE AMPLIFIER ..... ............. ............. ............ ............. .............223.3 AMPLIFIER CONTROLLER DISPLAY (LCD) ........... ............. ............ ............. .............253.3.1 DEFAULT MENU ............. ............. ............ ............. ............. ............ ............. .............25

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3.4 AMPLIFIER CONTROLLER KEYPAD ......... ............. ............. ............ ............. .............263.5 MENUS .......................... ............. ............ ............. ............. ............ ............. .............273.5.1 DEFAULT MENU: ............ ............. ............ ............. ............. ............ ............. .............273.5.2 SYSTEM AND TUBE HOURS MENU: ....... ............. ............. ............ ............. .............273.5.3 DC TUBE TEST MENU: .. ............. ............ ............. ............. ............ ............. .............283.5.4 SYSTEM RF TEST MENU ............. ............ ............. ............. ............ ............. .............283.5.5 OPERATING PARAMETERS MENUS ...... ............. ............. ............ ............. .............283.5.6 MAINTENANCE MENU

... ............. ............ ............. ............. ............ ............. .............29

3.5.6.1 AUTO TESTS ON/OFF . ............. ............ ............. ............. ............ ............. .............303.5.6.2 SET PA BIAS MENU ..... ............. ............ ............. ............. ............ ............. .............303.5.6.3 SET IPA BIAS MENU .... ............. ............ ............. ............. ............ ............. .............313.6 TEST CONNECTOR J1 .... ............. ............ ............. ............. ............ ............. .............313.7 FRONT PANEL PUSHBUTTONS ... ............ ............. ............. ............ ............. .............32

4.0 USING AND SERVICING THE AMPLIFIER ......... ............. ............. ............ ............. .............334.1 GENERAL .......................... ............. ............ ............. ............. ............ ............. .............334.2 SAFETY PRECAUTIONS ... ............. ............ ............. ............. ............ ............. .............334.3 INSTALLATION ................... ............. ............ ............. ............. ............ ............. .............344.3.1 INSPECTION ................... ............. ............ ............. ............. ............ ............. .............344.3.2 LINE FREQUENCY (50/60 Hz) SELECTION

.......... ............. ............ ............. .............34

4.3.3 AC LINE (MAINS) CONNECTION: ............ ............. ............. ............ ............. .............354.3.4 MRI SYSTEM INTERFACE CONNECTIONS ......... ............. ............ ............. .............354.3.4.1 RS-232 Control J905 (See Figures 2 & 6) ............ ............. ............ ............. .............364.3.4.2 GND CTRL J901 (5-PIN LEMO CONNECTOR) . ............. ............ ............. .............374.3.4.3 MUX CTRL J902 (TWINAX CONNECTOR) ........ ............. ............ ............. .............374.3.4.4 RF ENABLE - J904 (See Figures 2 & 6) ............. ............. ............ ............. .............384.3.4.5 RF INPUT - J900 (See Figures 2 & 6) ... ............. ............. ............ ............. .............384.3.4.6 RF OUTPUT - J502 & J506 (See Figure 2) .......... ............. ............ ............. .............384.4 SAFETY INTERLOCKS ..... ............. ............ ............. ............. ............ ............. .............384.4.1 LOGIC SHUTDOWN INTERLOCK ............ ............. ............. ............ ............. .............384.4.2 SYSTEM INTERLOCK

.... ............. ............ ............. ............. ............ ............. .............39

4.4.3 OTHER SAFETY FEATURES ....... ............ ............. ............. ............ ............. .............395.0 DIAGNOSTICS AND TROUBLE SHOOTING ..... ............. ............. ............ ............. .............40

5.1 DETAILED LISTING OF FAULT CODES ..... ............. ............. ............ ............. .............405.2 WARNING CODES ............. ............. ............ ............. ............. ............ ............. .............485.3 MODULE REPLACEMENT ............. ............ ............. ............. ............ ............. .............495.3.1 LIQUID CRYSTAL DISPLAY (LCD) MODULE ........ ............. ............ ............. .............495.3.2 AMPLIFIER CONTROLLER MODULE ...... ............. ............. ............ ............. .............505.3.3 LED (DISPLAY) PCB ....... ............. ............ ............. ............. ............ ............. .............505.3.4 56 VOLT REGULATOR MODULE ............ ............. ............. ............ ............. .............515.3.5 100 WATT SOLID STATE DRIVER MODULE ......... ............. ............ ............. .............525.3.7 PA TUBE

.......................... ............. ............ ............. ............. ............ .............53

5.3.8 IPA TUBE REMOVAL ...... ............. ............ ............. ............. ............ ............. .............555.3.9 IPA TUBE INSTALLATION ............ ............ ............. ............. ............ ............. .............565.3.10 SERIAL CONNECTOR .. ............. ............ ............. ............. ............ ............. .............565.3.11 PA CAPACITOR BANK AND HV RECTIFIER BOARD ....... ............ ............. .............565.3.12 IPA CAPACITOR BANK ............. ............ ............. ............. ............ ............. .............585.3.13 FUSE REPLACEMENT . ............. ............ ............. ............. ............ ............. .............58

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5.4 FIELD ADJUSTMENTS ...... ............. ............ ............. ............. ............ ............. .............585.4.1 PA CONTROL PCB ADJUSTMENTS ........ ............. ............. ............ ............. .............585.4.2 TUNING .......................... ............. ............ ............. ............. ............ ............. .............60

6.0 PERIODIC MAINTENANCE ....... ............. ............ ............. ............. ............ ............. .............626.1 INSPECTION ........................ ............. ............ ............. ............. ............ ............. .............626.2 ROUTINE CLEANING AND REPLACEMENT ............ ............. ............ ............. .............626.2.1 EVERY 30 DAYS .............. ............. ............ ............. ............. ............ ............. .............626.2.2 EVERY 90 DAYS

.............. ............. ............ ............. ............. ............ ............. .............62

6.2.3 ANNUALLY ....................... ............. ............ ............. ............. ............ ............. .............626.3 FUNCTIONAL CHECK ....... ............. ............ ............. ............. ............ ............. .............63

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1.0 OVERVIEW OF AMPLIFIER ORGANIZATION ANDOPERATION

1.1 GENERAL

The 51-S21F-64 is a fully automatic linear RF amplifier capable of delivering 74 dB of gain and 25 KW of output at 64.05 MHz. The 51-S22F-42 are fully automatic linear RF amplifiers capable of delivering 72 dBof gain at 15 KW output at 42.30 MHZ. Figures 1 and 2 show a front and back view of the amplifier.

The 51-S2#F-XX consists of a two-stage, grounded-grid vacuum tube amplifier driven by a three-stage,solid-state driver. The grounded grid amplifiers provide approximately 25 dB of gain. The remaining gainis supplied by the solid state driver and preamplifier.

 All major functions of the amplifier are controlled and monitored by a microprocessor (uP)-based controlsystem. Amplifier control is local via front panel push buttons or remote via RS-232 communications. Afour line Liquid Crystal Display (LCD) provides system status and diagnostic information.

1.2 FUNCTIONAL BLOCK DIAGRAM

Figure 3 is a functional block diagram of the 51-S2#F-XX. The system includes four major assemblies :The Amplifier Controller, RF Amplifier deck, Low Voltage Power Supply (LV tray), and the High VoltagePower Supply.

1.2.1 Amplifier Controller 

The Controller provides all system control, monitoring and diagnostics. User interface is via front panelpush buttons or via RS-232 communications. To facilitate service it incorporates a display and keyboard toallow local control and display of system information. The controller is located at the front of the Low

Voltage tray.

1.2.2 RF Amplifier  Deck

The RF Amplifier Deck includes the following assemblies:

1) Solid State Driver (100W SS Driver)2) Intermediate Power Amplifier (IPA)3) Power Amplifier  4) PA Control board5) System Regulator board (56V Regulator)

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1.2.3 Low Voltage Power Supply

The Low Voltage Power Supply (Low Voltage PS tray) contains the following:

1) All primary power switching and distribution.2) A ferro-resonant supply that provides power for the filaments, tube bias, solid state

driver/preamplifier, and control relays.3) A supply that provides power for the Controller and the system blowers.4) The System Controller which is located at the front of the LV tray.

1.2.4 High Voltage Power Supply

The High Voltage Power Supply (HV Deck) includes the following:1) Primary power input connector.2) EMI filter.3) A ferro-resonant supply to provide anode voltage for the PA and IPA.4) The power supply cooling fan.

1.2.5 Ferro-Resonant Supplies

The ferro-resonant supplies use constant-voltage transformers to regulate the secondary voltages as theprimary input is varied from 187 to 229 VAC.

1.3 MODES OF AMPLIFIER OPERATION

Operating modes and corresponding maximum rated peak output power of the RF amplifier include:

HIGH (BODY) 25.00 KW peak 51-S21F-6415.00 KW peak 51-S22F-42

MID (A-5) 5.00 KW peak 51-S21F-64 and 51-S22F-42

Relay K1, K2, and K3 in the Solid State Driver module, K1 in the IPA/PA Input board, and relays K502,K503, and K504 in the PA/IPA deck configure the RF signal path as required for the various modes of operation (Reference Figure 4).

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1.3.1 MODE "HIGH (BODY)"

In the "HIGH (BODY)" power mode of operation, all stages of the amplifier are in use. The mode relays norelays in the Solid State Driver, K1 (IPA/PA Input board) and K502 are energized for this configuration. Therelays K503 and K504 are de-energized. The RF output goes to J502, a type "HN" RF connector at theback of the amplifier.

1.3.2 MODE "MID (A-5)"

In the "MID (A-5)" power mode of operation, all stages of the amplifier are in use. The mode relay K3 (100Watt SSA) is energized, K1 (IPA/PA Input board) and K502 are energized for this configuration. RelayK504 is energized. The RF output goes to J506, a type "N" RF connector at the back of the amplifier.

1.3.3 MODE "LOW (A-1)" (not specified)

51-S21F-64In the "LOW (A-1)" power mode, the mode relay K2 is energized and the IPA is bypassed in the RF deck(K1 IPA/PA Input board andK502 de-energized).

51-S22F-42In the "LOW A-1)" power mode, the mode relay K2 is energized and the PA is bypassed in the RF deck(K502 and K505 energized).

The relay K504 is energized routing the RF output to J506, a type "N" connector at the back of theamplifier.

1.4 AMPLIFIER OPERATION, GENERAL

 Amplifier operation is fully automatic and controlled via front panel pushbuttons (see Figures 1 and 15) or via the RS-232 communications port, J905 (Figure 2). A four-line LCD provides system status anddiagnostic information. LEDs on the front panel give the operational state of the amplifier. In addition,there are several connectors on the back of the amplifier (see Figure 2) that provide for RF input (J900),RF output (J502 and J506), RF Enable (J904), Body/Head mode selection and hardware interlocks (J901and J902). Chapters 3 and 4 of this manual cover the pushbutton control, the RS-232 interface, and theconnections to the amplifier.

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Once the user selects the desired operating parameters and the amplifier is requested to go to Standby or Operate, the amplifier automatically executes the turn-on sequence, checks system operating conditions,positions relays, and sets power trip points. Correspondingly, when the system is requested to go to "Off",the turn off sequence is automatically executed.

The amplifier protects itself from most abnormal operating conditions by monitoring many internalparameters and shuts down if a fault condition is detected. A message through the RS-232 interface,which is shown on the LCD, will give a fault code and a brief description indicating what problem wasdetected in the amplifier. The amplifier cannot be damaged by an incorrect command input sequence.

Safety interlocks are provided to protect the amplifier, service personnel and the MRI system.

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 2.0 AMPLIFIER CONTROL

2.3.1 OVERVIEW

The amplifier control boards perform three major functions within the amplifier system:

1. Communication with the MRI control system.

2. Control of the amplifier hardware.

3. Monitoring of the amplifier functions for fault conditions.

2.3.2 CUSTOMER INTERFACE BOARD

Refer to Figure 49. All connections to the amplifier from the MRI System connect to the customer interfaceboard, which is located at the rear of the amplifier. The filters on this board provide EMI protection. Theexternal connections to the amplifier are described in Section 4.3.3 and 4.3.4 of the manual. Refer to thatsection of the manual for specific connector information.

2.3.3  LED DISPLAY BOARD

Refer to Figures 15, 46, and 47. The LED Display board is located on the front of the amplifier. The LEDDisplay board has three pushbutton switches: OFF, STBY, and OPER. These switches may be used toturn the amplifier on to the Standby State, the Operate State, or turn the amplifier "OFF".

NOTE: When the front-panel RS-232 test connector is being used, the three front-panelpushbuttons are disabled.

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The LED Display board provides status LEDs (OFF, WAIT, STANDBY, OPERATE, ENABLE, and FAULT)which show the state of the amplifier or indicate when a fault has occurred. The same signal (Solid StateEnable) that gates the amplifier "ON" and "OFF" drives the ENABLE LED. This ensures a positive indica-tion when the amplifier is un-blanked (enabled).

Included on this board is a DB-9 male connector (J1) which is anRS-232 port that can be used by servicepersonnel to gain control of the amplifier from the front panel. When this port is used for system control, J2and J4 on the rear panel are automatically disabled, and, the three pushbuttons on this board are disabled.

The pushbuttons and LED serial data are multiplexed on the SWITCH/LED DATA line. The DIAG INcontrol line is used to write to the LEDs (DIAG IN low) or read from the pushbuttons (DIAG IN high). Themicroprocessor on the Amplifier Control board controls this multiplexing. When the RS-232 TestConnector J2 is being used, the DIAG IN line is pulled low all the time by the user of the Test Connector.This lets the microprocessor know that the Test Connector is being used. Since the DIAG IN line is heldlow by the user, the front panel pushbuttons are disabled.

2.3.4 AMPLIFIER CONTROLLER BOARD

Refer to Figures 15 ,44 and 45-45i. The Amplifier Controller provides system-level monitoring and controlof the individual sections of the amplifier. The amplifier Controller has four basic sections (Ref. Figure 41) : Processor, Control Interface, Digital input/output and Analog input/output. The Amplifier Controller mountsto the front of the Low Voltage Power Supply deck (Ref. Figure 15).

The control lines to the PA Control module connect to J302 via a 40-pin ribbon cable. The individualcontrol lines to the high- voltage and low-voltage power supplies connect to J304 and J305. The Customer Interface Board connects to J301 via a 40-pin ribbon cable. The LED board connects to J306 via a 16-pinribbon cable. The 12-volt, 24-volt and ground connections are via J307.

2.3.4.1 CONTROL PROCESSOR SECTION

Refer to Figures 44 and 45b. The Control Processor section is the heart of the amplifier control system. Ituses the Intel 8031AHmicro controller (U34), with supporting EPROM code memory (U31), RAM datastorage (U23), nonvolatile RAM (U20), semi-custom Logic Cell Array (U3) and bus decoders. A watchdogreset circuit (U36) provides the power-on reset and a hardware reset if the firmware or hardware is notoperating correctly.

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The watchdog reset circuitry provides an important safety feature for the amplifier. At power-on, thiscircuitry provides a 1.6-second positive reset pulse to the micro-controller (RST) and a negative (/RST)pulse to the rest of the amplifier controller. This allows time for the 5-volt supply and the clock oscillator toturn on and stabilize. The watchdog chip develops the pulse timing internally. The watchdog circuitprovides the logic high at pin 9 of the Intel 8031 micro-controller needed to reset the micro-controller. TheRST and /RST control lines ensure that the amplifier is completely shut down, all supply voltages (exceptthe 12-V controller supply) are turned off, and the RF path is completely disabled.

When the 1.6-second reset pulse returns low, the Intel 8031 micro- controller enters the main control loop,which provides the control for the amplifier. The watchdog circuitry attempts to force another hardwarereset every 100 milliseconds. Every time the control firmware executes the control loop, it sends out ashort-duration (1 to 2 microsecond) positive pulse on pin 3 of the micro-controller, preventing the watchdogchip from resetting the controller. If the program has a fault, or takes too long completing the control loop,or a hardware fault occurs which interrupts the proper operation of the micro-controller, the watchdogcircuitry generates a reset pulse which resets the micro- controller and the amplifier. This action immedi-ately disables the RF path (BLANKED), the power supplies are shut off and the amplifier returns to the"OFF" state.

The Firmware (amplifier control software) resides in the 32K EPROM (U31) and is socketed. Whenreplacing the amplifier Controller, the new Controller must have a Firmware EPROM with the same versionof software as the one being replaced. If It becomes necessary to update the Firmware, pull the oldFirmware EPROM out carefully and install the new EPROM. Take care to be sure that the new FirmwareEPROM is in the right direction and that no pins bend.

The semi-custom Logic Cell Array (U3) has the tasks of controlling the blanking, analog input line selection,tube overcurrent protection, and MRI System control interface.

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The Logic Cell Array contains the hardware interlock circuitry for the amplifier UN-BLANK control. Thiscontrols the gating on and off of the amplifier stages. Four conditions must be met to gate the amplifier on:

1) The amplifier must be in the OPERATE state.

2) The Logic Shutdown control line must be at a logic  low, or zero volts.

3) The System Interlock control line must be at a logiclow, or zero volts.

4) The Blank In control line must be at a logic low,or zero volts.

The Logic Cell Array selects which amplifier stages to un-blank, based on mode. The hardware interlockcircuitry does not require micro-controller interaction in order to gate the amplifier stages off. When theamplifier controller detects a fault within the amplifier, the amplifier firmware turns off the OPERATE statecontrol line, gating off the amplifier.

2.3.4.2 CONTROL INTERFACE SECTION

Refer to Figures 40, 45h, and 45i. The Control Interface section handles the communications interface tothe MRI System computer. This includes RS-232, hardware control interfaces and interlock lines.

Note : The amplifier is controlled via the RS-232 only in the "C" version of the amplifier. The connectionsto HEAD/BODY, System Interlock, MUX+ and MUX- are not used by the system.

The Intel 8031 micro-controller on the Amplifier Controller handles the asynchronous communicationinterface directly. The buffer chip U16 (Ref. Figure 45i) converts the 5-volt logic level to the +/- 10-volt logiclevels of the RS-232 interface.

 A single jumper (JP2) selects the asynchronous communications baud rate. The supported baud rates are300, 1200, 2400, and 9600. At the end of each message, the Amplifier Controller transmits CarriageReturn and Linefeed characters to the MRI System to disable the final character, a jumper maybe installed at the position marked "NO LF". This causes the final character not betransmitted. During the power-on initialization or after a hardware reset, the micro-controller detects thestate of the jumpers.

 A 20-volt regulator (VR1, Figure 45h) supplies +20 volts to the MRI system through pin 1 of J901. This 20volts is switched in the MRI system and returns to the amplifier to select the Body/Head modes of operation, and is used for the System Interlock line.

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The BODY/HEAD select line (from J901 pin 2) connects to the opto-isolator U12 on the control board(figure 50). When the BODY/HEAD select line is at 20 volts, the Body mode of operation is selected.When the line is at zero volts (or open), the Head mode of operation is selected.

The SYS_INTLK (System Interlock) control line (from J901 pin 3) connects to the opto-isolator U11 on thecontrol board (figure 45i). When this line is at 20 volts, the amplifier operates normally. When this line is atzero volts (or open), the amplifier RF is gated off, and if the amplifier is in the Operate State a Fault 43 beoccurs. Fault 43 clears as soon as 20 volts is restored to the SYS_INTLK control line.

The LOGIC SHUTDOWN interlock line (from J905 pin 18) connects to D5, D6, R21, and R22 (figure 50).This line is pulled to +5 volts by R22 and must normally be pulled low by the MRI system. If it is low (zerovolts), the amplifier operates normally. It it is high (or open), the amplifier gates the RF output off, causing aFault 42, and shutdown to the Standby State.

The MUX+ and MUX- control lines from Q3 and Q4 (figure 45i) go to J904. The MUX- control line is low(zero volts) when the SYS_INTLK line is at 20 volts. The MUX- line is high (+5 volts) when the SYS_INTLKline is at zero volts or open. The MUX+ line is high (+5 volts) when the BODY/HEAD Select line is at zerovolts or open (Head mode). The MUX+ line is low (0 volts) when the BODY/HEAD select line is at +20volts (Body mode).

2.3.4.3 ANALOG INPUT/OUTPUT SECTION

Refer to Figures 44, and 45f. The Analog Input section provides a method of monitoring up to 24 analogvoltages within the amplifier system. These voltages are digitized to 8-bit resolution over a range of zero to+5 volts. RC input filters on each of the analog input lines minimize RF interference. A voltage regulator provides a precision 5-volt reference for the A/D converter.

Over-voltage on one analog input channel can override another channel through the 4051 analog multiplexICs. This occurs if one of the analog input lines rises above +5 volts, a condition that must be checkedwhen troubleshooting the amplifier.

The Analog output section provides a method to output a voltage from 0 to +5 volts. The PA control boarduses this voltage to adjust the bias voltage during the DC tube tests.

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2.3.4.4 DIGITAL INPUT/OUTPUT SECTION

Refer to Figures 44, and 45d. The Digital Input section (Ref. Digital I/O Schematic Figure 45d) provides thecircuitry to monitor digital signals within the amplifier. The use of RC filters allows the digital input circuitryto operate in a high RF environment. The digital input section monitors the safety interlocks, airflow sen-sors, transformer thermal interlocks, 50/60 Hz selection jumpers, line frequency and filament currents.

The Digital Output section provides the circuitry for the Control Processor to drive relays and digital loads. All outputs are an open collector sink to ground and are low true.

Each of the digital latches (U17, U24) has a CLEAR line to the watchdog circuitry. The RST control linefrom the watchdog timer turns off the digital outputs when the micro-controller is reset (i.e., power-onwatchdog reset). This shuts off the power supplies (except the +12-volt supply), gates off the amplifier stages and de-energizes the RF path-selection relays.

When the PA control board senses an overcurrent condition in either the IPA or PA high-voltage sections, itinterrupts the amplifier controller board. The LCA chip (Logic Cell Array Figure 45c U3) disables the 24Vrelay driver turning off the high voltage and opening the RF path.

2.3.5  PA CONTROL BOARD

Refer to Figures 12, 29(a-d), and 30(a-d). The PA Control board provides the interface circuitry for signalsbetween the amplifier controller and the PA Deck. This board implements a number of functions, includingbias control, wattmeter scaling and control signal interconnection. This board mounts to the side of the PAdeck.

 All control connections between the Amplifier Controller and the PA control board connect via a 40-pinribbon cable connected to J400.

The vacuum-tube stages in the PA and IPA Amplifier Decks require bias voltages to set their operating andblanked states. The low voltage power supply provides 70 volts for the generation of this bias voltage.D34, D35, D45 and D46 rectify the 70 volts and C23 filters it for a nominal 100 VDC. Pull-up resistors R58and R59for the PA and R60 and 61 for the IPA raise the cathode voltages of the tube stages to a cutoff biasof 100 volts. The Amplifier Controller monitors the bias voltage for the IPA and PA tubes separately to en-sure that the cutoff bias voltages are correct. The bleeder resistor, R67, provides a safety function in that itwill discharge the bias supply before the vacuum tubes lose their cathode emission at amplifier turnoff.This assures a gradual discharge of the PA and IPA high-voltage supplies.

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The enable signals from the Amplifier Controller change the bias voltage from cutoff to class AB operation.The IPA-enable signal turns off Q6, which turns on Q2. The PA-enable signal turns off Q10, which turns onQ1. A series diode string on each bias transistor adjusts the operating voltage of each unblanked cathodeline. This sets the tube UN-blank idle current. The IPA and the PA stages have switch-selectableoperating bias (S2 and S1).

IPA and PA stage grid current flows through the bias transistors and shunt resistors R21 and R30,respectively. The Amplifier Controller monitors these resistors' voltages to be sure that the grids are notbeing over driven. The 20-VAC lines from the low voltage deck are rectified by D41- D44 to produce -25-volt DC. This voltage is used for the DC tube test and the unregulated input for the -15 VDC supply on the56-V PS module.

The LM-337 (VR1) regulates the -25 volts for the emission test. The Analog output from the Amplifier Controller, buffered by U6B, sets the output voltage of VR1. U6A converts and scales this negative voltageto a positive voltage that the Amplifier Controller monitors during DC Tube Tests. The regulated voltage (-V) passes to the IPA (Q3) or PA (Q4) bias line when the Emission Test Enable and the appropriate tubeenable line are low. This adjusts the bias voltage to check the tube's emissions.

Current transformers in the PA deck monitor the plate current flowing in the IPA and PA stages. Therectified, filtered and scaled current samples go to the Amplifier Controller for monitoring. Op-Amps U2Band U2A along with the associated circuitry amplifiers and buffers the plate current signals. During theBIAS set routine the scale factor of the buffer amplifiers is increased for better plate current resolution.Voltage comparators (U1A, U1C) monitor the current samples. If the comparators detect excessive currentin the PA or IPA high-voltage supplies, they signal the Amplifier Controller. The Logic Cell Array, on the Amplifier Controller, senses this condition and disables the 24-volt relay driver, causing the HV ON relay(Figures 16 and 33, K205) to de-energize and turn off the high voltage. High-voltage overcurrent trips of this type are usually due to high-voltage arcing inside the tube(s). If not stopped, the arcing can quicklydamage components.

The PA Control board scales the forward power signal. The Mode 2/3 control line selects the scalingfactor. When in mode HIGH (BODY), R3 sets the gain of the Forward Power buffer (U5B). When in modeMID (A-5) R7 sets the gain. R8 sets the gain of the Reflected Power buffer (U5A). R27 sets the gain of theSSA Forward Power buffer (U3A).

 A number of control signals connect directly from the Amplifier Controller through the PA Control board tothe RF Input module,100W-SS driver module, PA/IPA sections and the 56-volt Power Supply.

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3.0 CONTROL and COMMUNICATIONS

3.1 RS-232 SERIAL INTERFACE

The ETO amplifier is configured as a DTE, with a female 25-pin D Subminiature connector J904 on theback of the amplifier (Ref. Figure 2). Chapter 4 in this manual covers the pin-out of the connector.

The RS-232 parameters are:a) 8 data bitsb) 1 stop bitc) No parityd) Baud rate: ( jumper selectable JP-2 )

300 baud1200 baud2400 baud9600 baud

e) Control lines used:  CTS Clear To Send  DTR Data Terminal Ready

3.2  COMMAND FORMAT

 All command inputs are composed of upper or lower case ASCII characters terminated with a carriagereturn . Linefeed characters are ignored. The ETO Amplifier echoes each character as it is en-tered. Upon receipt of a carriage return, the command is decoded and executed. A carriage return andlinefeed are echoed for each carriage return received.

Valid Commands:

a) OPER=< OFF | STBY | ON | ? >

b) MODE=< SSA | LOW | MID | HIGH |  BODY | HEAD | ? >

c) FREQ=dd.dd or ?

d) AFT=< ON | OFF | ? >

e) PWR=hhh or ?

f) FPWR= ?

g) HOURS= < ? | AMP | PA | IPA | CLR PA | CLR IPA >

h) FAULT= < ? | 0 - 10 | CLEAR >

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i) WARN= < ? | 0 - 10 | CLEAR >

   j) TEST= < ON | OFF | TUBES | PA TUBE | IPA TUBE | RF | SSA RF | PA RF | AMP RF >

  k)  TUBE = ?

l) ATEST= < ON | OFF | ? >

Spaces after the equal sign and the case of the characters are ignored. Thus, the following commandinputs are equivalent:

OPER = STBYOper = stby

3.2.1 The OPER=< OFF | STBY | ON | ? > Command

The Amplifier has three main states of operation: OFF, STANDBY, and ON (or OPERATE). In the OFFstate, only the amplifier controller has power applied to it. The rest of the amplifier is shut down. The Am-plifier Controller monitors a few basic amplifier parameters and waits for the next command.

In the STANDBY state, the amplifier is powered up with no high voltage applied to the tubes. Enough time(3 minutes) is allowed for the amplifier to completely warm up. The Amplifier Controller is monitoring criticalparameters and waiting for the next input command.

In the ON (or OPERATE) state, the amplifier is ready for operation. It is completely powered up and highvoltage applied to the tubes. The Amplifier Controller monitors all critical performance parameters. Thecontroller waits for the next command.

OPER=OFF shuts the amplifier down to the OFF state.

OPER=STBY causes the amplifier to go to the STANDBY state.

OPER=ON causes the amplifier to go to the OPERATE state.

OPER=? causes the amplifier to return the present state of the amplifier, i.e. one of the following

s1_OFFs2_STBYs3_ONx1_WORKING.

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3.2.2 The MODE= < SSA | LOW | MID | HIGH |  HEAD | BODY | ? > Command

The MODE command reconfigures the amplifier for the proper RF output level at the defined RF outputconnector. The power levels are:

SSA 50 WattsLOW 500 Watts - 51-S21F-64 and 51-S22F-42MID (A-5) 5,000 Watts - 51-S21F-64 and 51-S22F-42HIGH (BODY) 15,000 Watts - 51-S22F-42

  25,000 Watts - 51-S21F-64

The mode "SSA" (Solid State Amplifier) is available for test purposes only. The high voltage is not turned onfor this mode of operation. The RF output of the SSA is dumped into an internal 50 ohm resistor, R44 (figure21).

The MODE command may be entered at any time.

 A MODE=? command returns the present mode the amplifier is set for, i.e. one of the following:

n0_SSAn2_HEADn3_BODY

3.2.3 The FREQ= dd.dd or ? Command

The FREQ= dd.dd command provides no useful purpose in this amplifier. It is provided solely for thepurpose of maintaining compatibility with the multi-frequency amplifier.

If a frequency is entered outside the range for which the amplifier was tuned, then the message:

"e2_AMPLIFIER NOT TUNED AT THIS FREQ/MODE"

is transmitted. No fault occurs if the amplifier is taken to Operate with an invalid frequency.

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 A FREQ = ? command returns the last frequency entered. Upon initial power-up, the amplifier defaults to63.72 MHz. For instance:

FREQ=? returns:r1_FREQ= 63.72 MHZ

3.2.4 The AFT=< ON | OFF | ? > Command

The AFT command provides no useful purpose in this amplifier. It is provided solely for the purpose of maintaining compatibility with the multi-frequency amplifier.

 An AFT sequence is provided at the end of the High Voltage On sequence if the AFT option is turned on.This sequence exactly simulates the AFT sequence in the multi-frequency amplifier in terms of themessages sent out and the control of the "AFTEN" control line. The AFT sequence does not peak thetuning in this amplifier.

The AFT=OFF command disables the AFT feature. The AFT=? command returns the present status of the AFT, i.e. AFT=? returns:

k2_ON or k1_OFF

 At initial power-on, the amplifier defaults to AFT=OFF.

3.2.5 The PWR= hhh or ? Command

The PWR=hhh command sets the maximum forward RF power that the amplifier will allow. The maximumRF power depends on the mode of operation of the amplifier. The "hhh" is a 2-or 3- digit hexadecimalnumber computed from the equation:

hhh = HEX[ k x P ] Where: P = Power in watts

k = 0.100 MODE MID (A-5)  0.010 MODE HIGH (BODY)HEX[ ] means to convert the decimal

  number to hexadecimal.

EXAMPLE: Set forward power trip point in mode HIGH (BODY) to10000 watts.

P = 10000 k = 0.010

k x P = 0.010 x 10000 = 100hh = HEX[ 100 ] = 64

PWR=64 will set the forward power trip point to 10000 watts.

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 A PWR= FFF command forces the forward power trip point to be set to the default value for the mode theamplifier is in. See below for the default values.

The forward power is sampled once every 330 microseconds. For the amplifier to declare a forward power Fault 95 and shutdown to the Standby State, the RF forward power must be greater than the set thresholdfor two consecutive samples, or 660 microseconds.

The PWR=hh command may be entered any time.

When the amplifier is commanded to go from Standby to Operate, one of the first checks in the high-voltage-on sequence is to insure that the power trip level setting is less than or equal to the maximumallowed for the mode the amplifier is in. If the power trip level setting is greater than the maximum allowedfor the mode, Fault 95 is declared and the amplifier is returned to the Standby state. The power-trip level isalso reset to the default setting for the mode the amplifier is in.

The maximum forward power-trip-level settings for each mode are:

  MODE MID (A-5) : 8E ... 1420 WattsMODE HIGH (BODY): D4 ... 21200 Watts

If the PWR=hhh command has not been used, or a Fault 95 occurs due to the PWR=hhh level being settoo high, or a PWR=FFF command is issued, the forward power trip limits are set to their default values.The default values are:

  MODE MID (A-5) : 8E ... 1420 WattsMODE HIGH (BODY): D4 ... 21200 Watts

 Any time the forward power trip level changes, the message: "r2_PWR= hhh" (hhh is the value the triplevel is set to) is transmitted.

 A PWR=? command returns the 2- or 3- digit hexadecimal number representing the maximum RF power level, i.e.

PWR=? returnsr2_PWR= hhh

The PWR=? command may be issued at any time.

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3.2.6 The FPWR= ? Command

This command returns the peak forward power out of the amplifier since the last time the command was is-sued.

The amplifier samples the forward power every 330 microseconds when the amplifier is in the Operatestate. The maximum power sampled is stored in memory. When the FPWR=? command is issued, theamplifier returns the maximum power sampled and then clears that memory location.

The format of the command is:

FPWR= ? returns:r3_FPWR= xx.x KWWhere xx.x is the forward power in kilowatts.

3.2.7 The FAULT= < ? | 0 - 10 | CLEAR > Command

The amplifier stores in nonvolatile RAM the last 10 faults that have occurred. This command allows accessto those faults for troubleshooting purposes.

The command returns the fault code the amplifier had along with a short description of the fault. The formatof the command is:

FAULT= ? or 0

which returns the last fault that occurred in the amplifier, e.g.

f1_FAULT 95 FORWARD POWER HIGH

The command: FAULT= 1 returns the fault that occurred before the "FAULT= 0". FAULT= 2 returns thefault that occurred before the "FAULT= 1" and so on. The last ten faults that occurred in the amplifier canbe determined by this process.

The FAULT= CLEAR command clears the fault code memory. After the amplifier is repaired this commandcan be used to restart the saving of fault codes.

3.2.8 The WARN= < ? | 0 - 10 | CLEAR > Command

The amplifier stores in nonvolatile RAM the last 10 warnings that have occurred. This command allowsaccess to those warnings for troubleshooting purposes.

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The command returns the warning code the amplifier had along with a short description of the warning.The format of the command is :

WARN= ? or 0

which returns the last fault that occurred in the amplifier:

x3_WARNING 21 PA GAIN LOW 

The command: WARN= 1 returns the warning that occurred before the "WARN= 0". WARN= 2 returnsthe warning that occurred before the "WARN= 1" and so on. The last ten warnings that occurred in theamplifier can be determined by this process.

The WARN= CLEAR command clears the fault code memory. After the amplifier is repaired this commandcan be used to restart the saving of warning codes.

3.2.9 HOURS=< ? | AMP | PA | IPA | CLR PA | CLR IPA >

The amplifier keeps track of the total hours that the amplifier has been on and the total fi lament hours of theIPA and PA tubes. This command is used to monitor the amplifier or tube hours. It may also be used toreset the hours to zero on the PA or IPA tubes. The total amplifier hours is not resettable.

The format of the command is:

HOURS= ? or AMPx3_AMP HOURS = 134H (up to 99999H)

HOURS= PAx3_PA HOURS = 134H (up to 99999H)

HOURS= IPAx3_IPA HOURS = 134H (up to 99999H)

The HOURS= CLR PA or CLR IPA is used to reset the clocks on the PA or IPA tube when that tube isreplaced during normal maintenance. The format is:

HOURS= CLR PAx3_PA HOURS = 0H

HOURS= CLR IPAx3_IPA HOURS = 0H

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3.2.10 TEST= < ON | OFF | TUBES | PA TUBE | IPA TUBE  RF | SSA RF | PA RF | AMP RF >

The amplifier has a number of self-test features to warn the user when the tubes are near end-of-life and tohelp the service technician locate system problems. This set of commands allows access to the self testroutines.

3.2.10.1 DC TUBE TEST DESCRIPTION

The "TUBES" tests check the dc parameters of the IPA and PA tubes. A warning message is sent out viathe RS-232 port, and also to the amplifiers LCD, if one (or both) of the tubes is near end-of-life. If the tubesare good, no message is sent out over the RS-232 port. The format for this command is:

TEST= < TUBES | PA TUBE | IPA TUBE >

3.2.10.2 RF TESTS DESCRIPTION

The "RF" tests check the RF performance of the amplifier. The amplifier contains either a 64-MHz or a 42-MHz oscillator which is only turned on for use in these tests. The amplifier also contains an internal 50-ohm load so that during the RF self tests all RF power remains within the amplifier. A warning message issent out via the RS-232 port, and also to the amplifier LCD, if one of these tests fails. If the tests pass, nomessage is sent out over the RS-232 port. The format for this command is:

TEST=RF

The "SSA RF" test checks the Solid State amplifier sections only. The oscillator and the solid stateamplifiers are gated on for a brief period, and the output of the Solid State Driver is monitored. If the outputlevel of the Solid State driver falls outside pre-defined limits, a warning message is sent out. Note: if theamplifier fails the SSA RF test, the PA RF and AMP RF tests cannot and will not be run. The SSA RF testis automatically run before the PA RF or AMP RF tests. The format for this command is:

TEST=SSA RF

The "PA RF" test checks the PA section of the amplifier (the IPA stage is bypassed). The oscillator, solidstate driver, and PA stage are gated on for a brief period of time. The RF is applied to an internal 50 ohmload. The gain from the solid state driver output through the PA tube is measured along with the RF droopover the pulse. If the gain or droop is out of tolerance, a warning message is issued. The format for thiscommand is:

TEST=PA RF

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The "AMP RF" test checks the IPA and PA stages combined. Note: the IPA stage cannot be testedseparately. The oscillator, solid state driver, IPA stage, and PA stage are gated on for a brief period of time. The RF is applied to an internal 50-ohm load. The gain from the solid state driver output through theIPA and PA stages is measured along with the RF droop over the pulse. If the gain or droop of thecombined IPA and PA stages is out of tolerance, a warning message is issued. The format for this com-mand is:

TEST=AMP RF

3.2.10.3 TEST COMMAND USE

To use the amplifier self-tests first issue the command:

TEST= ON

This enables the use of the self-test commands. The command:

TEST= OFF

disables the self-tests and turns off any tests not yet completed.

Note: The amplifier self-tests will be performed only at the end of the high voltage on sequence or when the amplifier is in the Operate state. If for example the command TEST= TUBES isissued while the amplifier is in the Standby state, nothing happens until the amplifier is given thecommand OPER= ON. At the end of the high-voltage-on sequence, the tube tests will then beperformed. If the amplifier is in Operate when the TEST= TUBES command is given, the tubetests will be immediately performed.

To test the tubes issue the command:

TEST= TUBES

This causes the testing of both the IPA and PA tubes. To test one of the tubes separately, issue thecommand:

TEST= PA TUBE or TEST= IPA TUBE

To test the amplifier RF performance, issue the command:

TEST= RF

This command will cause the testing of all the RF stages. First, the SSA RF test is executed, then the PARF test is run, and finally the AMP RF test is run. To run any one of these tests individually issue thecommand:

TEST= SSA RF or TEST= PA RF or TEST= AMP RF

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The amplifier message response to any one of the self-tests is (if issued from Operate):

TEST= TUBES

  Response (if passed): Response (if warning):

x1_WORKING x1_WORKING(short delay) (short delay)s3_ON x3_WARNING xx xx xxx3_READY (short delay)  s3_ON

Note: The warnings do not cause a fault in the amplifier. The amplifier always returns to Operate.Use the WARN= < ? |0 - 10 > command to get a descriptive message of the warning(s).

 All of these tests can be run using the amplifier keyboard and menu system (see section 3.4). Also theamplifier can be set up to run all of these tests automatically every 100 hours of amplifier use. See the"ATEST" command below.

3.2.11 TUBE= ?

This command performs the same functions as: TEST= TUBES, described in Section 3.2.10.

3.2.12 ATEST= < ON | OFF | ? >

The ATEST command is used to turn on or off the automatic testing of the amplifier every 100 hours of operation. The automatic self tests are designed to give early warning of tubes becoming weak. Thiscondition does not prevent the further use of the amplifier. The self tests performed are the dc tubeparameter tests and the RF tests described in Section 3.2.10. ATEST sets a flag in nonvolatile memory sothat after the main power has been removed from the amplifier, the amplifier will "remember" the last settingof this command.

If the command: ATEST= ON is issued, the amplifier will go through a self-test sequence approximatelyevery 100 hours of operation. The amplifier has a clock that monitors total time the amplifier is on. Everytime the amplifier goes from Standby-to- Operate (if the ATEST= ON command had been issued) itdetermines if it has been over 100 hours since the last self-test sequence has been executed.

If it has been over 100 hours, then the self-test sequence is run at the end of the high-voltage-onsequence. The self-test sequence takes less than 10 seconds, and there are no special messages sentout over the RS-232 interface indicating the sequence is taking place. If no problems are found during thetests, the amplifier will go to the Operate State, as normal.

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If the self-test sequence detects a condition out of tolerance, the message:

x3_WARNING xx

is sent out over the RS-232 interface. There may be more than one warning code included, depending onthe number of problems detected. Example:

x3_WARNING 03 21 22 indicates warning conditions 03, 21 and 22

 After issuing warning message, the amplifier enters the Operate State and is ready for use.

The command: ATEST= OFF turns off the self-test feature of the amplifier.

The command: ATEST= ? returns the status of the last ATEST command. Example:

 ATEST= ? returns: o5_A_TEST= ON  or o5_A_TEST= OFF

3.2.13. MESSAGES FROM THE AMPLIFIER

In response to each command entered, the amplifier issues a message to the MRI control systemindicating that the command has been received and is being executed. These messages also tell the MRIcontrol system the status of the amplifier. A two-digit alphanumeric string precedes each message to alloweasier decoding by MRI system software.

e1_SYNTAX ERROR This message is transmitted if an improper command is entered.

e2_AMPLIFIER NOT TUNED AT THIS FREQ/MODE

When a frequency/mode combination is given which results in a channelwhich the amplifier has not been tuned, this message is transmitted.

x1_WORKING This message is transmitted when the amplifier leaves the OFF state,STANDBY state or the ON state to perform a task followed by one of thetwo following messages.

m1_STATE CHANGE IN PROGRESS

This message signifies the amplifier changes states, e.g., going from theOFF state to the STANDBY state, from STANDBY to ON.

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m2_FREQUENCY/MODE CHANGE IN PROGRESS

This message signifies the amplifier is in the process of automaticallytuning to a new frequency/mode combination.

m3_AFT IN PROGRESS This message is issued when the amplifier is executing a simulated Au-tomatic Fine Tuning(AFT) sequence. This sequence is provided tomaintain compatibility with the multifrequency amplifier.

x2_DONE This message is transmitted when a Frequency/Mode change iscompleted or when AFT is completed.

s1_OFF This message is transmitted whenever the OFF state is entered.

s2_STBY This message is transmitted whenever the STANDBY state is entered.

s3_ON This message is transmitted whenever the ON state is entered.

x3_READY This message is transmitted whenever a commanded task is completed.

f1_FAULT xx "Short fault description" 

This message is transmitted whenever a fault in the system is detected.The xx is the fault number. The operations manual defines all fault codes.

When a Fault is detected by the Amplifier Controller, the amplifier automatically enters theSTANDBY state or the OFF state, depending on the type of fault (fatal or non- fatal).

When the FAULT=? command is issued, a short description of the fault follows the fault code.

x4_OK This message is transmitted after a fault is detected the amplifier enterseither the STANDBY or OFF state, provided there are no further faultspending in that state.

r1_FREQ= dd.dd MHZ This is the response to the FREQ=? command.

r2_PWR=hh This is the response to the PWR=? command. This message will also betransmitted any time the PWR=hh value changes.

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n0_SSA This is the response to the MODE=? command.n2_HEADn3_BODY

k1_OFF This is the response to the AFT=? command.k2_ON

x3_AMP HOURS = xxxxxH   ( 0 - 99999 )

x3_PA HOURS = xxxxxH ( 0 - 99999 )

x3_IPA HOURS = xxxxxH   ( 0 - 99999 )  This is the response to the HOURS= ? , AMP, PA, IPA command. The

"H" at the end stands for hours.

x3_WARNING xx "Short Warning description"

The warning message is in response to a self-test sequence if a problemis found. The additional "Short Warning description" is only sent inresponse to the WARN= < ? | 0 - 10 > command.

o5_A_TEST= ON Response to the ATEST= ? command.o6_A_TEST= OFF

EXAMPLES OF COMMANDS AND THE RESULTING MESSAGE SEQUENCE:

Beginning with amplifier Off:

OPER=STBYx1_WORKINGm1_STATE CHANGE IN PROGRESSs2_STBYx3_READY

If a command to change to a new, and valid, frequency and mode had been entered (with the amplifier OFF) before the OPER=STBY command, the message sequence would be:

OPER= STANDBYx1_WORKINGm1_STATE CHANGE IN PROGRESSm2_FREQUENCY/MODE CHANGE IN PROGRESSx2_DONEs2_STBYx3_READY

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From the Standby state:

FREQ= 63.72x1_WORKINGm2_FREQUENCY/MODE CHANGE IN PROGRESSx2_DONEx3_READY

OPER=ONx1_WORKINGm1_STATE CHANGE IN PROGRESSs3_ONx3_READYFault message sequence:

f1_FAULT 82x1_WORKINGs2_STBYx4_OK

When the primary AC power is first applied, the following message is transmitted:

E.T.O., INC.MODEL (amplifier model number)FIRMWARE PN: UPX-Xxxx-r COPYRIGHT (year released)

Note: in the Firmware part number the small x's are numbers and the small "r" is the revision level: A, B,

C...

3.3 AMPLIFIER CONTROLLER DISPLAY (LCD)

 A 4-line 20-character-per-line display is included as part of the Amplifier Controller (Ref. Figure 15). Thisreadout displays amplifier status information and facilitates local access, in conjunction with the Controller Keypad (Ref. 3.4), to system diagnostic and maintenance routines. The information is displayed in a seriesof menus, allowing selection of options.

3.3.1 DEFAULT MENU

The default menu top line displays the amplifier state or sequence of operation, such as OFF, STANDBY,OPERATE, POWER ONSEQUENCE, or HV ON SEQUENCE. These messages indicate the state the

amplifier is in.

The second line displays the mode of operation of the amplifier such as HEAD IMAGING, BODY IMAGING,or TEST SS AMPLIFIER.

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The messages in the third and forth lines vary depending on the status of the amplifier. When the amplifier is in the OFF,STANDBY or OPERATE state, the third line shows the amplifier hours of operation and thefourth line shows the amplifier model number and software version number.

During the Power-On sequence the third line displays a timer that gives the time, in seconds, remaining for filament warm-up. The filament warm-up time is 360 seconds.

If a fault occurs, the third l ine shows the fault code and the fourth line shows a short description of the fault.

3.4 AMPLIFIER CONTROLLER KEYPAD

The keypad, along with the display, allows local access to amplifier control and status without having to usethe MRI system console (Ref. Figure 15). The amplifier may be directed to execute OFF, STANDBY or OPERATE by using the keypad. The amplifier mode can also be set with the keypad.

The keypad works in parallel with the RS-232 control. The amplifier can be commanded to OFF,STANDBY, or OPERATE from either the push buttons or from the RS-232 interface. The amplifier does notdifferentiate the source of the command, it simply responds in the same manner to the same command.

The "LOCAL" button enables the use of the eight buttons to the right of (Ref. Figure 15). When the"LOCAL" button is pushed, the green LED comes on and the amplifier is in the LOCAL mode. This allowsuse of the other buttons described below.

When the "LOCAL" button is pushed again, the green LED goes out and the eight buttons described beloware disabled.

The "OFF" button commands the amplifier to go to the OFF state.

The "STBY" button commands the amplifier to go to the Standby state.

The "OPER" button commands the amplifier to go to the Operate state.

The "MODE" button toggles the amplifier between MODE= SSA, MODE= HEAD/BODY. The actualselection between the MID (A-5) and HIGH (BODY) modes of operation is done by the BODY/HEADSelection line (J901 pin 2).

The "MENU" button sequences the display through a group of menus (Ref. Section 3.5) that supplyamplifier status information and local access to system diagnostic and maintenance routines.

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The "UP" and "DOWN" buttons move the menu arrow, allowing selection of the desired operation.

The "ENT" button causes the operation selected with the arrow to be performed.

3.5 MENUS

 As the "MENU" key is depressed, a series of menus are displayed in the following order:

• Default Menu

• System and Tube Hours Menu

• DC Tube Test Menu – IPA & PA

• System RF Test Menu – SSA, SSA/PA, SSA/IPA/PA

• Operating Parameter Menu – PA (Ip), PA (Ig), Fwd Pwr 

• Maintenance Menu – Autotest (ON/OFF)

• Default Menu

3.5.1 DEFAULT MENU:

----------------------OFF STATEHEAD IMAGING AMP HOURS = xxxxxxETO 51-S2#F-XX

----------------------3.5.2 SYSTEM AND TUBE HOURS MENU:

When the menu key is pressed, the display indicates the accumulated amplifier and tube hours (Filament"ON" time). The tube hours can be reset to zero by using the UP/DOWN keys to choose the tube to bereset, and pushing the enter button. This will display a screen to verify your selection. If EXIT is selected,the tube hours will not be reset.

---------------------- ----------------------AMP HRS 123456 >EXIT>PA TUBE HRS 1234 Enter ZERO PA TUBE HOURSIPA TUBE HRS 1234 --------->

PA TUBE 1234---------------------- ----------------------

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3.5.3 DC TUBE TEST MENU:

This menu allows each tube to be individually tested under DC conditions. The desired test is selectedwith the UP/DOWN keys and the ENTER button depressed. The selected test is then performed. If thetest passed, a message is displayed and the operation can be exited by pressing "MENU" or "ENT". If atest failed, the system goes to the default menu and displays a warning message on line three.

Note: The system must be in OPERATE to perform these tests.

---------------------- ----------------------  DC TEST PA TUBE Enter DC TEST IPA TUBE>DC TEST IPA TUBE ------->

TEST PASSED

---------------------- ----------------------

3.5.4 SYSTEM RF TEST MENU

The next menu is for performing RF tests on the amplifier. The test to be conducted is selected with theUP/DOWN keys and the ENTER buttons. The selected test will run. If the test passed, a message isdisplayed and the operation can be exited by pressing "MENU" or "ENT".  If a test failed, the system goesto the default menu and displays a warning message on line three.

Note: The system must be in OPERATE to perform these tests.

---------------------- ----------------------  RF TEST SSA RF TEST SSA,PA >RF TEST SSA,PA Enter   RF TEST SSA,IPA,PA -------> TEST PASSED

---------------------- ----------------------

3.5.5 OPERATING PARAMETERS MENUS

 A set of three menu displays show various operating parameters of the amplifier. These displays are:

  ---> --->  1st

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To move between the three displays use the arrow keys or the ENT key.

The first display (which comes up when cycling through the menus with the MENU key) shows theoperating parameters of the PA tube (Plate Current: Ip in amps, Grid Current Ig in milliamps, and HighVoltage: HV in kilovolts) along with the forward and reflected RF power out of the amplifier. The PA HighVoltage "HV" display is accurate all the time. When the amplifier is shut down to Standby from Operate, thedisplay will show the high voltage bleeding down slowly. The other parameters (Ip, Ig, FWR PWR, & REFLPWR) only show the correct values when the amplifier is in Operate and being gated on and off.

NOTE: Due to the slow sample rate (333 micro seconds for the FWR PWR and REFL PWR andless than 1 millisecond for Ip, Ig, and SSD PWR) the displayed values for theseparameters will not be accurate for standard MRI pulse sequences. These displayedparameters are designed to be use with rectangular pulses of pulse widths greater than 1millisecond. The purpose of the displayed parameters is to aid in the service of theamplifier only.

The second display shows the operating parameters of the IPA tube (Plate Current: Ip in amps, GridCurrent Ig in milliamps, and High Voltage: HV in kilovolts) along with the forward RF power out of theamplifier and the drive power out of the 100 watt Solid State Driver. The IPA High Voltage "HV" display isaccurate all the time. When the amplifier is shut down to Standby from Operate, the display will show thehigh voltage bleeding down slowly. The other parameters (Ip, Ig, FWR PWR, & SSD PWR) only show thecorrect values when the amplifier is in Operate and being gated on and off.

The third display shows the exhaust air temperature coming out of the PA section of the RF deck indegrees C. This temperature reading will not be accurate much below 25 to 30 degrees C. Thetemperature at the base of the PA tube is also displayed in degrees C. This temperature will read down toabout 0 degrees C. The temperature readings should give a valid temperature reading anytime theamplifier is on. The readings will not be valid when the amplifier is in the OFF state.

3.5.6 MAINTENANCE MENU

This menu accommodates toggling the auto tests (DC Tube Tests and System RF Tests) "ON" or "OFF"and has submenus for setting the PA and IPA tube bias. The menu is shown as:

  ----------------------  >AUTOMATIC TESTS OFF  SET PA BIAS  SET IPA BIAS

----------------------

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3.5.6.1 AUTO TESTS ON/OFF

The auto tests (DC Tube Tests and System RF Tests) may be toggled on or off by placing the cursor arrow(use the up/down arrow keys) on the line: "AUTOMATIC TEST" and then press the "ENT" key. Theamplifier should then be cycled ON (it is not necessary to wait for the amplifier to reach the Standby or Operate State) and then to the OFF state. This will lock the selection into the EEPROM memory.

When the auto test is "ON", the DC Tube Tests and the System RF tests are performed automatically every100 hours when the amplifier goes from "STBY" to "OPERATE".

3.5.6.2 SET PA BIAS MENU

The Set PA Bias Menu allows the service person to easily set the PA tube bias with out the need for additional test equipment. Refer to section 5.4.1 of this manual for the procedure for setting the PA tubebias and the proper level to set the bias.

Starting from the Maintenance Menu use the UP/Down Arrow keys to place the cursor arrow on the line:"SET PA BIAS". Press the "ENT" key to enter this menu option. In order to set the Bias the amplifier mustbe in the Operate State. The menu displayed will appear as:

-------------------->PA BIAS SET: OFF PA Ip: MA SET FOR: 525 MA DONE--------------------

When this menu is entered the PA BIAS SET: will show "OFF". The amplifier remains in the Operate Stateand nothing happens. Pressing the "ENT" key with the cursor arrow on the top line will toggle the Bias setoption on and off. When the Bias Set option is on, the amplifier leaves the Operate State and goes to theWait State (the Wait LED on the front panel comes on). The amplifier then automatically gates the PA tubeon and off at a rate of 2 millisecond on and 100 milliseconds off. The "PA Ip: " line will display the PA tubeplate current. The dip switches S1 on the PA Control board (Figure 12 and 30) may be used to set the PAbias. The target plate current is shown in line three. The plate current should be set as close to this valueas the switch settings will allow.

This menu may be exited by using the Up/Down arrow keys to move the cursor arrow to the line: "DONE"and then pressing the "ENT" key. The "MENU" key may also be used to exit this menu. Note: the "PABIAS SET: " does not have to be turned OFF before exiting. This will be done automatically when exitingthe menu.

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3.5.6.3 SET IPA BIAS MENU

The Set IPA Bias Menu allows the service person to easily set the IPA tube bias with out the need for additional test equipment. Refer to section 5.4.1 of this manual for the procedure for setting the IPA tubebias and the proper level to set the bias.

Starting from the Maintenance Menu use the UP/Down Arrow keys to place the cursor arrow on the line:"SET IPA BIAS". Press the "ENT" key to enter this menu option. In order to set the Bias the amplifier mustbe in the Operate State. The menu displayed will appear as:

-------------------->IPA BIAS SET: OFF PA Ip: MA SET FOR: 100 MA DONE--------------------

When this menu is entered the IPA BIAS SET: will show "OFF". The amplifier remains in the OperateState and nothing happens. Pressing the "ENT" key with the cursor arrow on the top line will toggle theBias set option on and off. When the Bias Set option is on, the amplifier leaves the Operate State and goesto the Wait State (the Wait LED on the front panel comes on). The amplifier then automatically gates theIPA tube on and off at a rate of 2 millisecond on and 100 milliseconds off. The "IPA Ip: " line will display theIPA tube plate current. The dip switches S2 on the PA Control board (Figure 12 and 30) may be used toset the IPA bias. The target plate current is shown in line three. The plate current should be set as close tothis value as the switch settings will allow.

This menu may be exited by using the Up/Down arrow keys to move the cursor arrow to the line: "DONE"and then pressing the "ENT" key. The "MENU" key may also be used to exit this menu. Note: the "IPABIAS SET: " does not have to be turned OFF before exiting. This will be done automatically when exitingthe menu.

3.6 TEST CONNECTOR J1

Refer to Figure 15. A Test Connector, J1, has been provided on the front of the amplifier so that servicepersonnel are able top lug an RS-232 terminal in and take control of the amplifier. All commands andmessages defined in Section 3.2 are available, using the RS-232 terminal through the front TestConnector, J1.

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When an RS-232 terminal is connected to J1, the RS-232 communication to the MRI system is disabled,passing full control to the terminal attached to J1. As soon as the terminal is disconnected from J1, thecontrol returns to the MRI system.

NOTE: When the test connector, J1, is used, the front panel

  buttons, OFF, STBY and OPER are disabled.

The Test Connector, J1, description and pin-out are as follows (see Figure 15):

D Subminiature 9-pin Male (amplifier side) connector.

Pin Out:

2 RX Data to the amplifier.

3 TX Data from the amplifier 

4 DTR from the amplifier.

8 CTS to the amplifier  

9 DIAG IN: When this line is pulled to GND theRS-232 communications isswitched by the amplifier controller to the front TEST CONNECTOR.

When this line is left open or at +5 volts, the RS-232 communications is tothe MRI system.

5 GND (ground or amplifier common).

3.7 FRONT PANEL PUSHBUTTONS

There are three front panel pushbuttons that may be used to turn the amplifier on to the Standby State or Operate or to turn the amplifier off. Figures 1 and 15 show the location of these buttons. The threebuttons are:

OFF Turns the amplifier off to the OFF State.

STBY Turns the amplifier on the Standby State or shuts the amplifier down to theStandby State when the amplifier is in the Operate State.

OPER Turns the amplifier on to the Operate State.

NOTE: When the test connector, J1, is used, the front panel  buttons, OFF, STBY and OPER are disabled.

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4.0 USING AND SERVICING THE AMPLIFIER

4.1 GENERAL

This equipment is intended for use as part of a high-field magnetic resonance imaging system. The amplifier may be turned on to Standby or Operate and turned off using the front panel pushbuttons. The amplifier mayalso be remotely controlled via an RS-232 interface and an appropriate computer or terminal.

During service the amplifier may be operated locally by either attaching a terminal to the connector locatedon the front panel of the amplifier or by removing the front service panel and depressing the appropriatebutton on the Controller. Amplifier status and diagnostic information are displayed on the four line display lo-cated on the Controller assembly (Ref. Section 3.3, 3.4, & 3.5).

4.2 SAFETY PRECAUTIONS

*****************************************************************************************************************WARNING!

LETHAL VOLTAGES ARE PRESENT INSIDE THE POWER SUPPLY AND RF DECKS.

BEFORE REMOVING ANY COVER FOR ANY PURPOSE, UNPLUG THE MAIN ACSUPPLY AND WAIT AT LEAST THREE MINUTES FOR FILTER CAPACITORS TODISCHARGE FULLY. USE A SUITABLY INSULATED GROUNDING PROBE TOMOMENTARILY CONNECT EACH EXPOSED HIGH VOLTAGE POINT TO THECHASSIS BEFORE WORKING INSIDE ANY CHASSIS AREA.

DO NOT APPLY POWER WITH COVER(S) REMOVED AS DAMAGE TO TUBES ANDOTHER COMPONENTS IS LIKELY TO RESULT.

*******************************************************************************************************************

DO NOT PLACE HEAVY OBJECTS OR LIQUIDS ON TOP OF THE AMPLIFIER.

DO NOT BLOCK INPUT OR EXHAUST VENTS.

ETO, Inc. will supply, at the users request, any and all information that will assist service personnel inrepairing those parts of the equipment which are designed by ETO, Inc. to be serviceable in the field.

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4.3 INSTALLATION

1) Inspect the amplifier (Section 4.3.1)

2) Set the amplifier for the AC line frequency (Section 4.3.2).

3) Connect the AC mains (Section 4.3.3).

4) Make the necessary control connections to the MRI system (Section 4.3.4)

5) Connect the RF Input, RF Output, and RF Enable  (Sections 4.3.4.4, 4.3.4.5, and 4.3.4.6). 

Note: Ensure the amplifier is terminated (RF Output connection)in a load capable of handling the RFoutput power of this amplifier before operating the amplifier.

6) Refer to the MRI systems manuals for proper use of this amplifier in the MRI system. Section 3.0 of this manual covers the operating commands for this amplifier.

4.3.1 INSPECTION

It is recommended that the unit be inspected for physical damage which might have resulted from shippingand handling.

4.3.2 LINE FREQUENCY (50/60 Hz) SELECTION

The 55-S21B incorporates ferro-resonant supplies which must be configured for either 50 Hz or 60 Hzoperation (60 Hz is the factory default). To reconfigure the 55-S21B from one source type to the other:

1. Disconnect the primary power plug from the system.  Do not supply power for a period of 3 minutesassuring that the high voltage has discharged to a safe level.

2. Remove the 50/60 Hz service panel from the rear of the system and follow the directions located onthe panel (Ref. Figures 2 & 5). Replace the panel when complete.

3. Remove the panel covering the HV assembly (Ref Figures 1 & 7). Take care to unplug the power supply fan when removing the panel. Its connector is located behind the panel on the lower righthand side. Attach a shorting strap between PA HV+ and PA HV- on the HV Rectifier board (seefigure 38a). Also connect a shorting strap between IPA HV+ and IPA HV- on the HV Rectifier board.

Locate P103 on the HV Rectifier board and insert it in J103 for 50 Hz operation or J102 for 60 Hzoperation.

Locate P105 on the HV Rectifier board and insert it in J105for 50 Hz operation or J106 for 60 Hzoperation.

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Remove the shorting straps from the HV Rectifier board. Reconnect the power supply fan connector andreplace the HV front panel.

Note: This amplifier must be enclosed in an outer cabinet when operated in patient vicinity.

4.3.3 AC LINE (MAINS) CONNECTION:

Connector required: AMP Model Number 213173-1

The amplifier must be connected to the secondary side of an IEC compliant isolation transformer.

The amplifier uses 208 VAC +/- 10%, 50/60 Hz, single phase, 30 amps maximum (60 Hz is the factorydefault). Make the AC power connections to pins 1 and 3 of the connector. Make the earth groundconnection to pin 7, the center pin. The other connections are not used by the amplifier.

Power Cord recommended:UL listed Type S or SO, 3 or 5 conductor, AWG 10 (5.261mm^2) (not provided with amplifier).

4.3.4 MRI SYSTEM INTERFACE CONNECTIONS

The maximum allowable applied voltage to the RS-232 connections below is +/- 12 volts. All other inputsignals have a maximum allowable applied voltage of 5.25 volts except where noted. If these levels areexceeded, the amplifier could be damaged.

The MRI System Interface Connectors are:

1) J905 RS-232 Control2) J901 GND CTRL3) J902 MUX CTRL4) J905 RF ENABLE5) J900 RF INPUT6) J502 & J506 RF OUTPUT

The following pages cover the pin outs of these connectors.

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4.3.4.1 RS-232 Control J905 (See Figures 2 & 6)

D Subminiature 25-pin Female (Amplifier Side) Connector (See Figure 6)

  SIGNAL (PIN) DIRECTION DESCRIPTION

TX DATA (2) from AMP Serial ASCII coded alpha numericcharacters making up command echoes and statusresponses. (< -5 volts = 'Mark'. > +5 volts ='Space')

RX DATA (3) to AMP Serial ASCII coded alpha numericcharacters making up commands to the amplifier. ( <-5 volts = 'Mark'. > +5 volts = 'Space').

CTS (5) to AMP Control line that signalsthe amplifier that it can transmit data. This line mustbe at a logical high ( > +5 volts for the amplifier totransmit messages to the MR system controlcomputer.

DTR (20) from AMP Control line that signals theMR system control computer that the amplifier canreceive data. This line goes to a logical high ( > +5volts ) when the amplifier is ready to receive data.

Logic Shutdown (18) to AMP TTL level signal. A low orground is required to enable amplifier operation. If this line goes 'High' or open circuit, the amplifier willbe forced to the power off state. A 1K ohm pull-upresistor to 5 VDC is provided.

GND (1) (7) Signal Return Path

NOTE: While the amplifier may be run using the front panel pushbuttons without the use of the RS-232 interface, pin 18 of J905 must be pulled low (0 volts) for the amplifier to operate. A Fault42 will result in the amplifier if this pin is not pulled low.

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4.3.4.2 GND CTRL J901 (5-PIN LEMO CONNECTOR)

Note : This connector is provided but is ignored by the software.

  SIGNAL (PIN) DESCRIPTION

+20 Volts (1) +20 volt supply used for the Body/Head Select line

and the System Interlock line.BODY/HEAD SEL (2) +20 volts on this line will select the Body Imaging

Mode of operation. Zero volts or an open on this line

will select the Head Imaging mode of operation.

SYSTEM INTLK (3) +20 volts on this line allows normal operation of theamplifier. Zero volts or an open forces the RF output

of the amplifier to be gated off and a Fault 43 to bedisplayed.

4.3.4.3 MUX CTRL J902 (TWINAX CONNECTOR)

Note : This connector is provided but is ignored by the software.

  SIGNAL (PIN) DESCRIPTION

MUX+ (male pin amp side) This is an output interlock to the MRI system. TheMUX+ line will be high (+5 volts) when the

BODY/HEAD SEL line is at zero volts. The MUX+ linewill be low (0 volts) when the BODY/HEAD SEL line

is at +20 volts.

  MUX- (female pin amp side) This is an output interlock to the MRI system. TheMUX- line will be low (0 volts) when the SYSTEMINTLK line is at +20 volts. The MUX- line will be high

(+5 volts) when the SYSTEM INTLK line is at 0 volts.

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4.3.4.4 RF ENABLE - J904 (See Figures 2 & 6)

BNC Connector  - TTL level signal requiring a low or ground to electronically activate the amplifier stages sothat an RF signal can be amplified through the amplifier. A 1K ohm pull-up resistor to 5 VDC is provided.

4.3.4.5 RF INPUT - J900 (See Figures 2 & 6)

BNC Connector - RF input signal to the amplifier. Nominal input signal level to this connector is 0 dBm.Maximum input signal level is 10 dBm or 2.0 volts peak-to-peak.

4.3.4.6 RF OUTPUT - J502 & J506 (See Figure 2)

Body Imaging (15 KW peak RF power) J502: Type HN Connector.

Head Imaging (1 KW peak RF power) J506: Type N Connector. These two connectors are internally connected to the amplifier chassis ground through an RF choke. Do notapply a voltage of any level to this connector.

Do not operate the amplifier without the proper 50 ohm load connected to this RF output.

4.4 SAFETY IN