. PO Box 8099, Rochester NY 8 Tel:(585) 3 0 Fax:(585) 3 9375 info@marchandelec.com www.marchandelec.com (c)00. MB Push-pull tube amplifier www.marchandelec.com 585 3 0
Parts List A section R R R3 R R5 R R7 R8 R9 R0 R R C C C3 C V V 0K0 K00 M00 M00 K00 00K K00 00 Ohm 0.07uF,50V 0. F,50V 0.07uF,50V 0.7uF,50V AX7WA EL8 3W dual triode pentode B section R R R3 R R5 R R7 R8 R9 R0 R R C C 0K0 K00 M00 M00 K00 00K K00 00 Ohm 0.07uF,50V 0.uF,50V 3W C3 0.07uF,50V C 0.7uF,50V V AX7WA dual triode V EL8 pentode R3 R R5 R R7 R8 R9 R0 R R nu K00 9K K 0K0 K nu 3K9 K 80K CB C5 C C7 C8 C9 C0 0.uF 00uF,50V 00uF,50V 00uF,50V 330uF,5V 330uF,5V 0.00 uf L trimmer / W axial monolythic polypropylene Wire jumper D,,3, D5, D7 D8 D9 D0 D UF007 N58 UF007 N58 N53 UF007 ultra fast A diode 8V zener ultra fast A diode 8V zener 5.V zener LED ultra fast A diode IC SG55 DIP socket www.marchandelec.com 585 3 0
Q Q Q3 Q IRFP0 PNA IRF50 IRF50 NPN T P3 T+T / 0T AWG IRFP0 PNA IRF50 NPN Tubes AX7WA EL8 dual triode pentode 0 ' ' ' transformer P3 w. hardware transformer Hammond 08 -pos. small terminal blocks 3-pos. small terminal blocks -pos. small terminal blocks 9-pin tube socket -pin DIP socket # hex standoff # star lockwasher /3 x /" machine screw, /3 x /" machine screw, black buttonhead /3 x /" machine screw, black buttonhead /0 x /" machine screw, black buttonhead /0 hex nut MICA insulator TO7 Thermal grease MB circuit board rear panel top cover bottom cover stick-on rubber bumper Wood Base nameplate w. screws RCA connector, red, w. hardware Binding post, red Binding post, black BInding post guide power connector gauge wire, red gauge wire, black shielded wire, conductor 5, A universal power supply Packing list Resistors 7 3 8 00 Ohm K00 K 3K9 0K0 9K 00K 80K M00 K W W trimmer Capacitors 5 3 0.00 uf 0.07uF,50V 0. F,50V 0.7uF,50V 0.uF 00uF,50V 330uF,5V polypropylene axial monolythic Semiconductors 3 UF007 N58 N53 SG55 ultra fast A diode 8V zener 5.V zener LED switchmode converter www.marchandelec.com 585 3 0
Top view (component side) of assembled circuit board. The tube sockets are installed on the other side (solder side) of the board. www.marchandelec.com 585 3 0
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 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 R will be adjusted for.v filament voltage during initial checkout.. www.marchandelec.com 585 3 0
Assembly instructions for MB power amplifier. Assemble the main cicuit baord using the parts list above. Do not install the tube sockets at this time. Do not install Q (IRFP0) at this time. Attach the transistors Q3 and Q about / above the circuit board (do not shorten the leads). Note the 00 Ohm resistors are constructed by connecting two 00Ohm resistors together. See pictures above to help with installing the power transformer on the board. Attach the IRFP0 transistor to the main circuit board using three wires. Note that the IRFP0 is mounted to the top plate with a mica insulator and heat sink compound on both sides of the mica. Install the tube sockets on the solder side of the board. Use the top plate as a guide to make sure the sockets fit correctly. Mount Q to the top plate. Mount the output transformer to the top plate. Mount the circuit board to the top plate Attach the leads of the transformer to the circuit board. The leads are attached to the terminal blocks as follows: Red: V++ (near C5) Blue: P Brown: P Blue/yellow: not used Brown/Yellow: not used Run a wire from terminal block V++ to terminal block S Run a wire from terminal block S to terminal block S Attach wires to the terminal blocks: Black hookup wire to GND and red hookup wire to V++(near C8). These are for the 5V DC supply. Twist these two wires togeter. Black hookup wire to GND and red hookup wire to FB ( on -pos terminal block). These are for the feedback from the speaker terminals. Twist these two wires togeter. Shielded wire to IN abd GND (near R0). 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 5VDC 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 Ohm or 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 V. Should be.v; adjust with trimmer. Check V++; should be approx 75V. Now install tubes; Plate voltage should go down somewhat; like approx 0V. Filament voltage will be lower also; this is OK if above.0v Install bottom plate and rubber self-stick feet. Done. www.marchandelec.com 585 3 0
U NHAX7 RA k R5A 50K U NHAX7 RA R3A CA 7n RA 000k C3A 7n R7A 000k U NHAX7 RB k R5B 50K U3 NHAX7 RB 50K R3B CB 7n RB 000k R7B 000k C3B 7n R8A k R9A RA 0K R8B k R9B R 0K U5 RA 00 R0A 00k CA 0.7µ U R0B 00k CB 0.7µ RB 00 CA 0.µF CB 0.µF R k R5 9.K RA k RB k L 0H L 0H L3 80mH C7 00µF C 00µF C5 00µF plate plate vpp vpp tp input outputpost groundpost Hammond 08 Output transformer OUTPUT to SPEAKER EL8/BQ5 EL8/BQ5 --- C:\Phil\designs\a_amplifiers\mb\mbschematic.asc ---