A) Circuit Breakers Trip On Power-Up Or During Use 2-Channel Versions - Meyer Sound MP-4 Service Manual

III. Common Failure Modes:
A. Circuit breakers trip on power-up or during use:
2-Channel Versions
1. Do not reset the circuit breakers. If the circuit breakers are reset without first determining
the cause, further damage to the electronics may result.
Caution: If the breakers are reset and power is applied, the AC mains board could be damaged causing
a popping sound and a small amount of smoke. This occurs because the thermistor on the AC mains
board, normally used for soft start operation, behaves as a 5000 W load. This damage is a normal
reaction. However, the AC mains board, will have to be replaced due to possible thermistor damage and
relay arcing.
2. If the amplifier is in the speaker cabinet, remove the eight (8) large head screws that attach
the amplifier to the cabinet. Remove the amplifier from the cabinet slowly, taking care to
unplug the green speaker connector on the top side of the amplifier.
3. With the amplifier sitting on a firm surface, remove the four (4) screws from the amplifier
chassis cover and remove the cover.
4. Lay unit on either side and remove the six (6) screws from the bottom of the amp chassis.
5. Return the unit to the upright position and disconnect the audio signal cable from the
Control board by unlocking the gray ribbon cable connector.
6. Lift up the Amp/heatsink module in order to remove the white DC power harness from
the connector on the Amp/heatsink module.
Caution: Be careful not to overflex the circuit board when removing the power harness connector.
7. Lift the Amp/heatsink module out of the chassis and set aside. Do not remove the Control
board from the Amp/heatsink assembly at this time.
8. With the Amp/heatsink removed, 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) Center fan turns 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.
9. If the previous three conditions are met, the power supply circuits are probably func-
tioning properly. It is most likely that the Amp/heatsink module is damaged and will
need to be replaced. Refer to Meyer Sound Self Powered Series MP-2 Amp/Heatsink
Service Procedure (# 17.033.013.01) for replacement procedures.
Self-Powered Concert Series
Service Manual
MP-2/4 Amplifier
© 1998 Meyer Sound Laboratories, Inc. All rights reserved.
Doc #: 05.033.040.01
Rev.: A
Date: 08/31/98
Page: 13 of 26