Self-Powered Concert Series
Service Manual
MP-2/4 Amplifier
Doc #: 05.033.040.01
Rev.: A
Date: 08/31/98
Page: 24 of 26
© 1998 Meyer Sound Laboratories, Inc. All rights reserved.
If broken solder joints or burned resistors are found, the Audio Input board will need to be
replaced.
Note: Ground loops carrying high voltages can burn some resistors and traces in the Audio Input
board. To replace the board remove the screw on top of the board and unlock the XLR connectors from
their shells turning the small self -locking pins on the center of the XLR counterclockwise.
9. Replace the Audio Input Board with a known good board (either new or from another
unit), power up the unit and test it again. If signal is still not present, remove the chassis cover
from the amplifier and verify that the audio ribbon on the control board is properly
connected.
10. If all else fails, try replacing the Control board. Replace the Control board with a known
good Control board (make sure it is the same type) and retry. Refer to Meyer Sound Self
Powered Series TruPower Limiting Upgrade Procedure (# 17.033.042.01 for MP-2 and #
17.033.042.01 for MP-4).
11. If the unit still does not operate correctly, return it to the nearest authorized service center
for further evaluation.
1. Disconnect the audio signal from the source and see if the noise goes away. If the noise
goes away, there is a problem with the audio source.
2. If the noise does not go away, disconnect the audio cable from the amplifier. If the noise
goes away, check the wiring of the signal cable. The audio signal cable should be wired in
a "balanced" configuration; that is, the audio signal should be present between pins 2 & 3,
never between 1 & 2 or 1 & 3.
3. If the unit has hum or noise without a signal cable connected, turn the unit off and slowly
remove the amplifier from the cabinet.
4. With the amplifier sitting on a firm surface, remove the eight (8) small head screws from
the user panel.
5. While slowly removing the user panel, disconnect the audio signal cable from the input
board on the user panel by disengaging the gray connector. Also disconnect the AC input
connector (4 wire green connector) on the AC mains board.
6. Using a magnifying glass, inspect the solder joints of the Audio Input board for broken
solder joints. Inspect the locking gray connector, the XLR connectors and the Input polarity
switch. Check if resistors R2 and R3 (located in between the XLR connectors) are not burned.
H. Unit hums or has noise:
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