Marchand Electronics Inc.

Marchand Electronics Inc.PO Box 18099, Rochester NY 14618

Tel:(585) 423 0462 Fax:(585) 423 [email protected] www.marchandelec.com

(c)2006 Marchand Electronics Inc.

MB26 Push-pull tube amplifier

Marchand Electronics Inc www.marchandelec.com 585 423 0462

Parts List

A 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 0.22 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

C3 0.047uF,250V filmC4 0.47uF,250V filmV1 12AX7WA dual triodeV2 EL84 pentode__________________________________________

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

CB 0.1uF axial monolythicC5 100uF,250V aluminum electrolytic C6 100uF,250V aluminum electrolytic C7 100uF,250V aluminum electrolytic C8 330uF,25V aluminum electrolytic C9 330uF,25V aluminum electrolytic C10 0.001 uF polypropylene

L1 Wire jumper

D1,2,3,4 UF4007 ultra fast 1A diodeD5,6 1N5248 18V zenerD7 UF4007 ultra fast 1A diodeD8 1N5248 18V zenerD9 1N5232 5.6V zenerD10 LEDD11 UF4007 ultra fast 1A diode

IC1 SG2525 DIP16 socket


Q1 IRFP240 MOSFETQ2 PN2222A NPNQ3 IRF540 MOSFETQ4 IRF540 MOSFET

T1 P3622 2T+2T / 40T 26 AWG

Packing list

Resistors

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

Capacitors

1 0.001 uF polypropylene4 0.047uF,250V film2 0.22 F,250V film2 0.47uF,250V film5 0.1uF axial monolythic3 100uF,250V aluminum electrolytic 2 330uF,25V aluminum electrolytic

Semiconductors

6 UF4007 ultra fast 1A diode3 1N5248 18V zener1 1N5232 5.6V zener1 LED1 SG2525 switchmode converter

1 IRFP240 MOSFET1 PN2222A NPN2 IRF540 MOSFET

Tubes

2 12AX7WA dual triode2 EL84 pentode

1 transformer P3622 w. hardware1 transformer Hammond 16081 2-pos. small terminal blocks1 3-pos. small terminal blocks2 4-pos. small terminal blocks4 9-pin tube socket1 16-pin DIP socket6 #6 hex standoff6 #6 star lockwasher6 6/32 x 1/4" machine screw,10 6/32 x 1/4" machine screw, black buttonhead12 6/32 x 1/2" machine screw, black buttonhead1 4/40 x 1/2" machine screw, black buttonhead1 4/40 hex nut1 MICA insulator TO2471 Thermal grease1 MB26 circuit board1 rear panel1 top cover1 bottom cover4 stick-on rubber bumper1 Wood Base1 nameplate w. screws1 RCA connector, red, w. hardware1 Binding post, red1 Binding post, black1 BInding post guide1 power connector 2' 22 gauge wire, red2' 22 gauge wire, black2' shielded wire, 2 conductor1 15, 4A universal power supply


Top view (component side) of assembled circuit board.The tube sockets are installed on the other side (solder side) of the board.


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..


Assembly instructions for MB26 power amplifier.

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.


U11NH12AX7

R2A1k

R5A50K

U1NH12AX7

R6A50k

R3A50k

C1A

47n

R4A1000k

C3A

47n

R7A1000k

U2NH12AX7

R2B1k

R5B50K

U3NH12AX7

R6B50K

R3B50k

C1B

47n

R4B1000k

R7B1000k

C3B

47n

R8A1k

R9A50k

R1A

10KR8B1k

R9B50k

R16

10K

U5

R12A200

R10A100k

C4A

0.47µ

U4

R10B100k

C4B

0.47µ

R12B200

C2A

0.22µF

C2B

0.22µF

R141k

R15

19.1K

R11A

1k

R11B

1k

L1

20H

L2

20H

L3

80mH

C7

100µF

C6

100µF

C5

100µF

plate1 plate2

vpp

vpp

tp1

input

outputpost

groundpost

Hammond 1608Output transformer

OUTPUT to SPEAKER

EL84/6BQ5 EL84/6BQ5

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Marchand Electronics Inc.

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