Behringer PMH 2000

Digital DJ mike · 28th June 2010, 08:24 PM

I have a Behringer Europower PMH 2000 that gets distorted nad hums after about 30 minutes. I disconnected the front panel and connected and audio signal to the 1 and 4 pins of the P2502 board where the front panel connects to and it played well, never shutting down. Also the T23 simiconductor gets very very hot. Its marked MRC 431. I tried looking it up and can't find it. Any help???

Enzo · 29th June 2010, 01:49 AM

T23 on the power amp is the fan drive, it was originally a BD239 type. If the fan is running, it can get warm. Behr often prints teh part types on teh board, I forget if on this model. Is ther a small 239 printed next to the part?

There are a couple ICs on the power amp that have their own +/-15v rails that are zener derived. There are ALSO a pair of 7815/7915 voltage regulators for the front panel - the mixer portion. When your hum arrives check both those regulated rails. Of one is collapsing or its filter cap going away, that could be the cause. Also try just resoldering the filter caps for those low voltage supplies - C33,34 and C30,57

This is a stereo amp, are both left and right affected, or just one side? It hums, so do ANY of the controls have ANY effect on that hum?

And I would also go down the board and check the output pins of each op amp, looking for DC offset.

28th June 2010, 08:24 PM	#1
Digital DJ mike diyAudio Member Join Date: Jun 2010	Behringer PMH 2000 I have a Behringer Europower PMH 2000 that gets distorted nad hums after about 30 minutes. I disconnected the front panel and connected and audio signal to the 1 and 4 pins of the P2502 board where the front panel connects to and it played well, never shutting down. Also the T23 simiconductor gets very very hot. Its marked MRC 431. I tried looking it up and can't find it. Any help???

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29th June 2010, 01:49 AM	#2
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	T23 on the power amp is the fan drive, it was originally a BD239 type. If the fan is running, it can get warm. Behr often prints teh part types on teh board, I forget if on this model. Is ther a small 239 printed next to the part? There are a couple ICs on the power amp that have their own +/-15v rails that are zener derived. There are ALSO a pair of 7815/7915 voltage regulators for the front panel - the mixer portion. When your hum arrives check both those regulated rails. Of one is collapsing or its filter cap going away, that could be the cause. Also try just resoldering the filter caps for those low voltage supplies - C33,34 and C30,57 This is a stereo amp, are both left and right affected, or just one side? It hums, so do ANY of the controls have ANY effect on that hum? And I would also go down the board and check the output pins of each op amp, looking for DC offset.

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