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Marchand Electronics Inc.PO Box 18099, Rochester NY 14618
R1 10K0 1% metal filmR2 1K00 1% metal filmR3 49K9 1% metal filmR4 1M00 1% metal filmR5 49K9 1% metal filmR6 49K9 1% metal filmR7 1M00 1% metal filmR8 1K00 1% metal filmR9 49K9 1% metal filmR10 100K 1% metal filmR11 1K00 1% metal filmR12 200 Ohm 3WC1 0.047uF,250V filmC2 0.22 F,250V filmC3 0.047uF,250V filmC4 0.47uF,250V filmV1 12AX7WA dual triodeV2 EL84 pentode
B section
R1 10K0 1% metal filmR2 1K00 1% metal filmR3 49K9 1% metal filmR4 1M00 1% metal filmR5 49K9 1% metal filmR6 49K9 1% metal filmR7 1M00 1% metal filmR8 1K00 1% metal filmR9 49K9 1% metal filmR10 100K 1% metal filmR11 1K00 1% metal filmR12 200 Ohm 3WC1 0.047uF,250V filmC2 0.22uF,250V film
R13 nuR14 1K00 1% metal filmR15 19K1 1% metal filmR16 2K21 1% metal filmR17 10K0 1% metal filmR18 2K21 1% metal filmR19 nuR20 3K92 1% metal filmR21 2K trimmerR22 180K 1/2 W
4 100 Ohm 2W7 1K00 1% metal film2 2K21 1% metal film1 3K92 1% metal film3 10K0 1% metal film1 19K1 1% metal film8 49K9 1% metal film2 100K 1% metal film1 180K 2W4 1M00 1% metal film1 2K trimmer
Detail view of power supply.Note the mounting of the transformer and the 5 leads.
The 3 leads from the primary are soldered into holes A,B and C. The twisted lead goes into hole marked B.The 2 leads from the secondary are soldered into holes D and E.
The leads are magnet wire with poly insulation; this insulation will melt away with the heat from the soldering iron.When soldering these leads apply enough heat for enough time until the insulation is gone.
The trimpot R21 will be adjusted for 12.6V filament voltage during initial checkout..
Assemble the main cicuit baord using the parts list above.Do not install the tube sockets at this time.Do not install Q1 (IRFP240) at this time.Attach the 2 transistors Q3 and Q4 about 1/2” above the circuit board (do not shorten the leads).Note the 200 Ohm resistors are constructed by connecting two 100Ohm resistors together.See pictures above to help with installing the power transformer on the board.Attach the IRFP240 transistor to the main circuit board using three 2” wires.Note that the IRFP240 is mounted to the top plate with a mica insulator and heat sink compound on both sides of the mica.
Install the 4 tube sockets on the solder side of the board.Use the top plate as a guide to make sure the sockets fit correctly.
Mount Q1 to the top plate.Mount the output transformer to the top plate.Mount the circuit board to the top plateAttach the leads of the transformer to the circuit board.The leads are attached to the terminal blocks as follows:Red: V++ (near C5)Blue: P2Brown: P1Blue/yellow: not usedBrown/Yellow: not used
Run a wire from terminal block V++ to terminal block S1Run a wire from terminal block S2 to terminal block S1
Attach wires to the terminal blocks:Black hookup wire to GND and red hookup wire to V++(near C8). These are for the 15V DC supply.Twist these two wires togeter.Black hookup wire to GND and red hookup wire to FB ( on 4-pos terminal block). These are for the feedback from the speaker terminals.Twist these two wires togeter.Shielded wire to IN abd GND (near R10). Connect the shield to GND, center wire to IN.Mount the top plate assembly to the top of the wood base, with all wires sticking out of the rear opening.Install all connectors to the rear panel.:RCA connector, Power connector, Binding Posts.The 15VDC wires are connected to the Power connector: red wire is center post.The feedback wires are connected to the binding posts: black to black, red to red.The shielded wire is connected to the RCA connector.Now the secondary wires from the transformer are connected to the binding posts.Use the diagram on the box for 8 Ohm speaker.Make sure the black wire fromthe transformer goes to the black binding post and the yellow wire to the red binding post.It is also possible to use the connections for 4 Ohm or 16 Ohm (depending on the loudspeaker)In any case, the black wire should be connected to the black binding post.
Amplifier should be functional now.Do not install tubes yet.Adjust the trimmer potentiometer as follows:Connect the DC power supply.!! Warning: high voltage will appear on circuit board. !!The LED should be on, indicating plate voltage.Check the filament voltage (between GND and pin H (next to P) on V1.Should be 12.6V; adjust with trimmer.Check V++; should be approx 275V.Now install tubes;Plate voltage should go down somewhat; like approx 240V.Filament voltage will be lower also; this is OK if above 12.0VInstall bottom plate and rubber self-stick feet.Done.