Marchand Electronics mb401 User Manual

Marchand Electronics Inc.

PO Box 473, Webster, NY 14580

Tel:(585) 872-0980 Fax:(585) 872-1960

[email protected] http://www.marchandelec.com

MB401 300 Watt MOSFET Power Amplifier

500W into 4 Ohm 300W into 8 Ohm

1

Features

The MB401 is a mono MOSFET power amplifier for high quality audio reproduction. The construction is all heavyduty. The amplifier is housed in an aluminum chassis. Heatsinks on the rear of the unit provide the cooling. Inside is a toroidal power transformer and power supply with large storage capacitors. The amplifier is designed for use with a 4 or 8 Ohm load, but it is stable with any output load. .

XLR Balanced inputs Balanced inputs for high noise immunity RCA Standard line level inputs Selector switch Switch between balanced and standard inputs Binding Posts Connection for the loudspeakers Fuse Protects the amplifier in case of overload Thermal cutout Protects the amplifier in case it gets too hot Power entry connector Standard line cord for 120V AC 1-phase operation.

Specifications.

Frequency response: 20Hz - 20KHz +/- 1 dB Harmonic Distortion @ 1KHz, 10W 0.02% or better Sensitivity 1.28VRMS Voltage gain 32dB(40X) Input impedance (RCA) 500 KOhm Short circuit output current 20 A peak, 15A Continuous Output load 8 or 4 Ohm, stable with any load Max power output 500W into 4 Ohm, 300W into 8 Ohm Power requirement 120VAC, 6A fuse; 240 VAC available Construction All metal cabinet, black with white legend Dimensions: 17” x3.5” x 11” (WxHxD) Weight: 22 lbs

MB401 Power Amplifier

Left

Inputs

In Out

Full Range

In in in in in in out

PR41 Preamplifier

Figure 1 Typical Sound System

MB401 Power Amplifier

In Out

Right

2

Inputs

MB401 Power Amplifier

In Out

Left

High

In in in in in in out

PR41 Preamplifier

in out hi out lo

Electronic Crossover

XM6, XM9, XM16 or XM26

Figure 2 Sound System with 2-way Electronic Crossover Network

MB401 Power Amplifier

In Out

MB401 Power Amplifier

In Out

MB401 Power Amplifier

In Out

Right

Left

Low

Right

3

Figure 3: Inside view. Note the placement of the MB401 power amplifier board (mounted on heatsink on the rear of the unit) and the PS112 power supply board; (mounted onto the bottom of the chassis) . The toroidal power transformer is mounted near the left of the unit on the baseplate.

4

Figure 4 Rear view of the amplifier.

Figure 5 Inside view of the rear panel

5

Assembly Instructions for the MB401 Kit.

Parts list.

Qu. Description 1 MB401 board assembly

1 PS112 board assembly 1 chassis base 4 rubber feet 4 #6 x ½” selftap 1 front panel 1 front panel spacer 1 rear panel 3 heatsink 2 1.0” standoff 5 0.5” standoff 1 500VA xformer + hardware 1 RCA connector 1 XLR connector 1 fuse holder 1 fuse, 6A slowblow 1 power entry connector 1 speaker terminal connector 1 DPST power on/off switch 1 DPDT slide switch 1 thermal cutout 2 handles 4 6/32 x 5/8” sockethead 1 resistor 2.4KOhm, 2W 2 #6 solder lug 2’ heatshrink 1/8” 1’ heatshrink 1/4” 7 8/32 x 1/2” socket head 16 8/32 x 1/2” panhead 23 #8 split lockwasher 7 6/32 x 3/8” flathead 5 6/32 x 1/2” flathead 1 6/32 x 1/2” black flathead 1 6/32 x 1/2” oval head 7 6/32 x 1/4” panhead 6 #6 kepsnut 5 #6 split lockwasher 6 4/40 x 1/2” panhead 2 4/40 x 1/2” flathead 8 #4 kepsnut

2‘ 22 ga wire brown 2‘ 22 ga wire red 2‘ 22 ga wire orange 2‘ 18 ga wire brown 2‘ 18 ga wire red 2‘ 18 ga wire orange 1/2‘ 22 ga wire green/yellow UL 3‘ 22 ga black UL 3‘ 22 ga white UL 1 heatsink compound 1 line cord 1 Hex L-Key 3/32" 1 Hex L-Key 7/64" 1 Hex L-Key 9/64"

Assembly instructions.

Before assembling the MB401 amplifier complete the assembly of the MB401 power amplifier board and the PS111 power supply board.

Rear panel: Remove the rear panel from the cabinet before starting this assembly. Mount the following parts to the rear panel: 1 DPDT switch

using 4/40 x 1/2" panhead + kepsnut.

1 XLR connectors

using 4/40 x 1/2" panhead + kepsnut. 1 RCA connectors, . 1 Pair of binding posts 1 Fuse holder 1 Power entry module.

using 4/40 x 1/2" panhead + kepsnut. 1 Thermal cutout

using 4/40 x 1/4" flathead + kepsnut Now mount the rear panel to the chassis using 5 6/32 x 1/2" flathead screws and kepsnuts. Note that the chassis bottom has a large hole in the bottom. This hole is used to mount the transformer. This hole should be on the left side of the chassis, as seen from the front. Now mount the 3 heatsinks to the rear of the chassis. Make sure all previous steps have been completed because some screws can not be reached after the heatsinks have been monted. Use 16 8/32 x 1/2" screws for this. Do use split lockwashers on all 14 screws.

Front panel: Mount the front panel and front panel spacer to the chassis using the 4 6/32 x 5/8"

6

sockethead screws and the handles. Use lockwashers

Rubber washers Use two of these.

with these screws. Install the fifth screw in the bottom of the panel. Use a 6/32 black flathead with kepsnut for this.

Feet: Install the 4 rubber feet in the bottom of the cabinet using the #6 selftap screws.

Transformer: Install the transformer. See figure below.

Chassis grounding. Solder the 2400Ohm, 2W resistor to a solder lug. Solder a length of black wire to the other end of the resistor. Install solder lug under one of the hex standoffs of the MB401 board. Connect the wire the GROUND connection (terminal marked G of the three position terminal block) of the MB401 board. This will connect the chassis of the amplifier to the DC ground of the power supply.

!!!! Assembly is now complete. !!!!

PS112 Power supply: Install the power supply next to the power transformer using 5 hex 1/2" standoffs, as shown in fig x. Use 6/32 x 3/8 flatheads on the bottom and 6/32 x 1/4" panheads on top.

MB401 power amplifier board: Install the board onto the heatsink with the 7 8/32 bolts with hex head. Use a lock washer with each bolt. Access to the mounting bolts is difficult. Use a long hex-wrench for this. IMPORTANT: Use heat sink compound to cover the rear of the MB401 mounting bracket completely before installing. Locate the board as far to the right (away from the xformer) as possible. Use the two 1" hex standoffs to secure the board to the bottom plate.

Wiring: Wire up the rear panel according to the circuit diagram.

Wiring note: Use the #22 wire with the thick insulation for the AC wiring to and from the power transformer. Use the #18 wire for the wire to the loudspeaker terminals and between the PS111 and the MB401 board. Use #22 wire for all other interconnect.

Initial power up.

The first time power is applied observe any unusual events, like smoke, etc. Turn the power off immediately if this happens and check for correct construction. It is best to power up initially using a variable power transformer (variac) and observe operation at about half line voltage. The bias current of the amplifier board now needs to be adjusted. Connect a DMM between testpoints TP1 and TP2. With no signal on the input and no loudspeaker connected use R33 to set the bias of the MB401 main amplifier board to 50mV. The heatsinks will become warm during normal operation. When the amplifier is powered up but no power is delivered the heatsink should become just slightly warm to the touch. If they become hot in this mode check the bias current of the MB401 amplifier module. With full AC voltage applied the V+ reading should be approx. 80V (referred to ground), the V- reading -80V, the V++ reading +92V and the V-- -92V.

Metal Plate

Chassis bottom

Figure 6 : Mounting of power transformer

Nut

Bolt

Rubber washer

Transformer

7

Red (18)

red

yellow

blue

gray

black

white

Rear Panel

Red

Yellow

Blue

Gray

white

black

orange

brown

black

white

orange

brown

black

Red(22)

Power entry

Front

panel Power switch

Rear panel

Wire to Case

Green/ yellow

L

DPDT switch

Circuit

breaker

w.

light

N

Thermal

cutout

Toroidal

Power

Transformer

*** primary connections shown for 120V line

AC

CT

V++

GND

V--

AC

PS112

TA TB TC TD

V+

GND

V-

Brown(22) Orange(22)

Brown(18) Orange(18)

V++ GND V--

MB401

V+ GND V-

Toroidal

Power

Transformer

***connect primary like this for 240V line

Toroidal

Power

Transformer

***use black wires with xformer with single primary

MB401 Power Amplifier

Power wiring

8

inv

GND

non

out

GND

RED

BLK

brown

RCA

G

red

RCA

red

XLR

orange

12

3

brown

MB301 Power Amplifier

Signal Wiring

IN

2 3

XLR

1

Figure 7 : Rear panel wiring for signal and speaker.

Orange(22)

Brown(22)

Red(22)

MB301

Speaker

Red(18)

Brown(18)

Binding

Posts

Use heavy 18 gauge wire for the speaker wires only

9

Assembly instructions for the MB401 main amplifier board.

Parts List

ID Value Description

Resistors

R1 1.00M 1%, 1/4W, Metal Film R2 1.00M 1%, 1/4W, Metal Film R3 24.9K 1%, 1/4W, Metal Film R4 24.9K 1%, 1/4W, Metal Film R5 1.00M 1%, 1/4W, Metal Film R6 1.00M 1%, 1/4W, Metal Film R7 1.00M 1%, 1/4W, Metal Film R8 10.0K 1%, 1/4W, Metal Film R9 10.0K 1%, 1/4W, Metal Film R10 100 Ohm Trimmer Potentiometer R11 not used R12 100 K 1%, 1/4W, Metal Film R13 2.00K 1%, 1/4W, Metal Film R14 2.00K 1%, 1/4W, Metal Film R15 2.00K 1%, 1/4W, Metal Film R16 499 Ohm 1%, 1/4W, Metal Film R17 499 Ohm 1%, 1/4W, Metal Film R18 499 Ohm 1%, 1/4W, Metal Film R19 100 Ohm 1%, 1/4W, Metal Film R20 499 Ohm 1%, 1/4W, Metal Film R21 100 Ohm 1%, 1/4W, Metal Film R22 100 Ohm 1%, 1/4W, Metal Film R23 Jumper R24 Jumper R25 not used R26 100K 1%, 1/4W, Metal Film R27 not used R28 100K 1% ,1/4W, Metal Film R29 not used R30* 49.9 Ohm 1%, 1/4W, Metal Film R31*1 Ohm 5W Wirewound R32*2.00K 1%, 1/4W, Metal Film R33 10 K Trimmer Potentiometer R34* 49.9 Ohm 1%, 1/4W, Metal Film R35*1 Ohm 5W Wirewound R36*2.00K 1%, 1/4W, Metal Film R37 not used

*8 places

Capacitors

C1 1.0uF Stacked Film C2 1.0uF Stacked Film C3 1pF Ceramic NPO C4 1pF Ceramic NPO C5 47uf, 100v Aluminum Electrolytic C6 47uf, 100v Aluminum Electrolytic C7 1000 pF Ceramic Disk

C8 4.7uf, 250v Aluminum Electrolytic C9 4.7uf, 250v Aluminum Electrolytic C10* 2200uf, 80v Aluminum Electrolytic,SF C11 6800uf, 6.3v Aluminum Electrolytic C12 6800uf, 6.3v Aluminum Electrolytic C13 6800uf, 6.3v Aluminum Electrolytic C14 0.22uf Stacked Film C15 6800uf, 6.3v Aluminum Electrolytic C16* 2200uf, 80v Aluminum Electrolytic,SF

* 4 places SF Snap Fit

Diodes

D1 1N4735 6.2 Volt Zener Diode D2 1N4148 Signal Diode D3 1N4148 Signal Diode D4 1N4148 Signal Diode D5 1N4148 Signal Diode D6 1N4735 6.2 Volt Zener Diode D7 LED D8 1N4148 Signal Diode D9 1N4148 Signal Diode D10 not used D11 Jumper D12 not used D13 Jumper D14 1N4735 6.2 Volt Zener Diode D15 1N4735 6.2 Volt Zener Diode D16 HER106 1 Amp. Diode D17 HER106 1 Amp. Diode

Transistors

Q1* ZVNL120A N-Channel SS MOSFET Q2* ZVNL120A N-Channel SS MOSFET Q3 ZVNL120A N-Channel SS MOSFET Q4 ZVP2120A P-Channel SS MOSFET Q5 ZVP2120A P-Channel SS MOSFET Q6 ZVNL120A N-Channel SS MOSFET Q7 ZVNL120A N-Channel SS MOSFET Q8 MTP2P50E P-Channel MOSFET Q9 MTP2P50E P-Channel MOSFET Q10 IRF710 N-Channel MOSFET Q11 IRF710 N-Channel MOSFET Q12 not used Q13 not used Q14 2N2222 NPN transistor Q15 2N2907 PNP transistor Q16 IRFI640 N-Channel Power MOSFET Q17** IRFI640 N-Channel Power MOSFET

10

Q18** IRFI9640 P-Channel Power MOSFET *Q1,Q2 come as a matched pair

**Q17 & Q18 8 places each matchesd sets Q9,Q11,Q12,Q13 need heatsink

1 2N2222 NPN transistor 1 2N2907 PNP transistor

* Matched sets of power transistors

Mechanical

The MB401 main board kit contains the following parts:

Qu. Value Description

Resistors

16 49.9 Ohm 1%, 1/4W, Metal Film 3 100 Ohm 1%, 1/4W, Metal Film 4 499 Ohm 1%, 1/4W, Metal Film 19 2.00K 1%, 1/4W, Metal Film 2 10.0K 1%, 1/4W, Metal Film 2 24.9K 1%, 1/4W, Metal Film 3 100K 1%, 1/4W, Metal Film 5 1.00M 1% ,1/4W, Metal Film 1 100 Ohm Trim Pot, 10 turn 1 10 KOhm Trim Pot, 10 turn 16 1.0 Ohm 5W Wirewound

Capacitors

2 1.0uF Stacked Film 2 1pF NPO Ceramic 1 1000 pF Ceramic Disk 1 0.22uf. Stacked Film 2 4.7uf, 250v Aluminum Electrolytic, R 2 47uf, 100v Aluminum Electrolytic, R 4 6800uf, 6.3v Aluminum Electrolytic, R 8 2200uf, 80v Aluminum Electrolytic, SF R: radial SF: snapfit

Diodes

4 1N4735 6.2 Volt Zener Diode 6 1N4148 Signal Diode 2 HER106 High Efficiency Diode 1 LED

Transistors

Quantity Description 2 3 Pos. Terminal block Blue

1 3 Pos. Terminal block Black 1 4 Pos. Terminal block Black 17 4/40x3/4” Machine Screw 17 4/40 Nut 17 #4 flat washer 34 #4 split lockwasher 1 Heat Sink Bracket 2 TO220 heatsink, TALL 1 Bag Heat Sink Compound 1 MB401 circuit board 2 testpoint

Assembly Instructions

Most parts are installed in the usual way. Insert the part at the location on the circuit board as indicated by the silk screen identification and solder on the solder side of the board. Start with installing smaller parts and install large parts last. This makes installation easiest. The circuit board has plated through holes, so parts need only be soldered on the solder side of the board.

Resistors: The 1% metal film resistors are identified with colored bands in the usual way. The 1% Metal film resistors have the following markings:

49.9 Ohm Yellow-White-White-Gold--Brown 100 Ohm Brown- Black -Black-Black--Brown 499 Ohm Yellow-White -White -Black--Brown

2.00 K Red -Black-Black-Brown--Brown

10.0 K Brown-Black-Black- Red --Brown

24.9 K Red-Yellow -White-Red--Brown 100 K Brown-Black-Black-Orange--Brown

1.00 M Brown-Black-Black-Yellow--Brown The multiturn trimmer resistors should be installed so

that the screw is at the location indicated by the white square.

1 pair ZVNL120A N-Channel SS MOSFET 3 ZVNL120A N-Channel SS MOSFET 2 ZVP2120A P-Channel SS MOSFET 2 IRF710 N-Channel MOSFET 2 MTP2P50E P-Channel MOSFET 9* IRFI640 N-Channel Power MOSFET 8* IRFI9640 P-Channel Power MOSFET

Jumpers: Install wire jumper is location J1 and any other locations as shown in the parts list, using bare hookup wire. Make sure the bare wire of the jumpers does not touch the surface of the circuit board.

Capacitors: The Electrolytic capacitors are all radial type. Be sure to observe polarity markings when installing. The stacked film capacitors are brown and have marking 224 for .22 uF and 105 for the 1 uF part.

Note: The orientation of caps C11 and C12 is not

Circuit board

4/40 x 1/2”

shown on the circuit board. They should be oriented the same way as C10 and C16.

Diodes: Diodes are installed in the usual way. Make sure to observe polarity: the band indicated on the circuit board must coincide with the band on the device. The band indicates the cathode.

Transistors: Transistors Q1…Q9, Q14, Q15 are the small black parts with the three leads. Note that the black part has a big flat side and a round side. Note that Q1 and Q2 come as a matched pair in a separate bag. Make sure to use these in the locations Q1 and Q2. Install the transistors according to the marking on the circuit board. Power transistors Q9 and Q11 are mounted with a heat sink. Q8 and Q10 need no heatsink. Power transistors Q16 through Q18 are installed onto the heat-sink bracket. Apply a thin uniform layer of the white silicone compound on the bottom of each transistor. Install the transistors with the 4/40 screws, two split lockwashers, flat washer and nut. See Figure 8. Orient the screws so that the head of the screw is on the solder side and the nut is on the component side. Solder the three transistor pins only after all the mounting screws have been tightened.

Header: Install the two 1-pin headers at locations TP1 and TP2. These are the testpoint that are used when adjusting bias.

Terminal Blocks: Install the two small 3-pin and large 3-pin and 4-pin terminal blocks at the edge of the circuit board.

The bias current of the amplifier must be adjusted by setting the potentiometer R22. First turn the potentiometer fully counterclockwise. This will set the bias current to zero. Hook the MB401 to a bipolar power supply. The supply voltage should be between +/- 30V and +/- 60 V. For doing this step it is best to use a 30V supply. This lower voltage will reduce chance of damage to the parts if there is an error in the installation of the parts. It is best to mount the MB401 onto a large heatsink during testing. Connect a DVM or suitable voltmeter between the testpoint TP1 and TP2. If the DMM indicates a voltage of more than a few mV turn the power off immediately and check all parts placements. A very safe way to do this step is to use a variac to increase the power supply voltage slowly from zero to about 30V, while observing the DMM. Now slowly adjust R33 clockwise until a reading of 15 mV is shown on the DMM. Precise adjustment is difficult. But a value between 10 mV and 20 mV is acceptable. Note that the unit will start heating up a little. The adjustment should be made when cold. When the amplifier is hot, the bias current will change a little. This is normal.

Offset adjustment.

The offset voltage of the amplifier must be adjusted by setting the potentiometer R10. With no signal applied to the inputs, adjust R10 for minimum DC voltage at the outputs. A residual output voltage of a few mV is normal.

The assembly and adjustment of MB401 circuit board is now complete.

Power supply.

Heat sink bracket

Nut

Heatsink compound

Flat washer

Split lockwasher

TO220 MOSFET

Figure 8 Mounting of power transistors.

Assembly is now complete. Take a few minutes to check all components and orientations. Also make sure there are no solder bridges.

Bias current adjustment (Class AB) .

The power supply used is the PS112. It has two separate sets of outputs, one for the preamp part of the amplifier board and one set for the output stage. The preamp voltage is about 20V higher than the voltage for the output stage.

Output voltages of the PS112

(with 55V transformer)

V+ +80V

V- -80V

V++ +100V

V- - -100V

R11

R4

R5

C4

Q11

R30 A,B,C,D,E,F,G,H

C10A,B,C,D

Q16

R17

R10

C11

Q14

C6

C5

R14 D8

C13

C15

R32 A,B,C,D,E,F,G,H

D9

D5

D3

R12

in+

in-

gnd

V++

V--

R15

Q4 Q5

R20

R21

R18

R19

Q8 Q9

R33

C14

on heatsink

Q6

Q7

R16

C7

D14

D15

D17

R22

D16

R26

Q15

R28

C12

R25

R29

R37

R36 A,B,C,D,E,F,G,H

R34 A,B,C,D,E,F,G,H

R27

Q17A,B,C,D,E,F,G,H

R31 A,B,C,D,E,F,G,H

R35 A,B,C,D,E,F,G,H

Q18 A,B,C,D,E,F,G,H

Q3

R13

R7

D4

D1

D7

Q10

R8

R9

Q1 Q2

D2

D6

V+

out

gnd

V-

C16 A,B,C,D

C3

C2

R3

C1

R1R2

R6

MB401 MOSFET Power Amplifier