Self-Powered Concert Series
Service Manual
MP-2/4 Amplifier
Doc #: 05.033.040.01
Rev.: A
Date: 08/31/98
Page: 17 of 26
© 1998 Meyer Sound Laboratories, Inc. All rights reserved.
19. At this point the top and bottom amp/heatsink are disconnected but the AC mains board
is in place and connected. Reset the breakers, and apply AC power to the power supply.
Verify the following conditions:
a) Audible power-up sequence (three clicks).
Note: This applies to AC supplies ranging from 110-130 V and 225-250 V. For AC supplies between 90-
105 V and 180-215 V, only two clicks will be heard.
b) Top and bottom center fans turn on.
c) Power supply LED’s on (visible through the top of the chassis)
Note: The user panel LED will not light as the Amp/heatsink module is disconnected.
20. If the previous three conditions are met, the power supply circuits are probably
functioning properly. It is most likely that one or both of the Amp/heatsink modules is
damaged and will need to be replaced. If any of the previous three conditions are not met,
continue to step 21.
Note: If you are going to replace the Amp/heatsink module, make sure that the AC Mains board is in good
conditions and not stressed checking the thermistor for cracks or visible burns. If the thermistor is damaged the
AC Mains module should also be replaced. (Use steps 7 to 10 to gain access to the AC mains board). The drivers
should be also tested, refer to Driver Inspection and Evaluation Procedure for Self Powered Series Products
(Low Driver #17.010.120.01 and High driver #17.010.120.02).
To determine which Amp/heatsink module is damaged, perform the following short circuit
evaluation:
Caution: Never disassemble the amplifier PCB board from the heatsink.
MP-4 top and bottom Amp/heatsink module evaluation:
a) Allow the Amp/heatsink modules to discharge any residual voltage (about 3 minutes).
b) Remove the Control board from each Amp/heatsink module by disengaging the locking
standoffs and remove the 15 pin header from the header connector.
Caution: Make sure to keep the Control board paired with its respective Amp/heatsink module.
c) Select an Amp/heatsink module and locate the top side of the board MOSFETs Q4A, Q1A,
Q2A, Q5A, Q4B, Q1B, Q2B, Q5B. They are 8 large devices mounted on the heatsink sink each with
3 leads connecting to the board.
d) Using an ohmmeter (set to ohms, not diode check), measure the resistance between the drain
and source of each FET.
Note: Each FET will have three leads - Gate, Drain, and Source. The Gate is the one with the square pad
on the board, while the Drain and the Source are the ones with the round pads.
e) If any FET has a resistance of less than 5 ohms, the module will need to be replaced. Refer to
Meyer Sound Self Powered Series MP-4 Amp/Heatsink Service Procedure (#17.033.013.02).
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