Behringer A500 Amp Problem Guidance

[KP11520]

Hi Fellas,

I have searched through all the threads on this amp and I have a situation that is different and I need help to resolve it.

The amp has 2 Channels (Left or Channel 1 and Right or Channel 2). No matter what input used (RCA, 1/4 inch or Balanced) and the variable gain set to max on both channels, Channel 1 is faint with no Bass when compared with Channel 2, which is loud and has appropriate Bass. I have reversed inputs with the same results, so it is with the amp.

Any help or ideas as where and how to look would be GREATLY Appreciated!

Below is the schematic I found on another thread here (Thanks). Hopefully it can be downloaded.

Thanks again!

Regards//Keith

[sreten]

Hi,

Yuo need to carefully compared the two channels, could be duff input IC's
or coupling capacitors as the most likely, or possibly duff supplies to one
channels circuit part, carefully check the worlking channel against the other.

If you have a multimeter that can read low AC voltages and a test tone
generator that can help, noting the overall feedback loops when working
control overall gain.

rgds, sreten.

[KP11520]

Hi sreten,

Thank you kind sir for giving me direction. What you suggest makes so much common sense that I should be whipped for not thinking of that.

I don't have a signal generator and have never used one or traced something like that through. I do however have an new Agilent U1242a DMM and it does quite a bit. So I will start with reading and comparing the mrrored Coupling Cap values. The symptoms do indicate a decent chance for that being the problem. If that's the problem I will do both channels with better Caps. If not..... I'll be back! LOL

Actually I'll be back to find what kind of Caps will do the job best! So either way, I'll see you soon.

Thanks again!

Regards//Keith

Originally Posted by sreten

Hi,

Yuo need to carefully compared the two channels, could be duff input IC's
or coupling capacitors as the most likely, or possibly duff supplies to one
channels circuit part, carefully check the worlking channel against the other.

If you have a multimeter that can read low AC voltages and a test tone
generator that can help, noting the overall feedback loops when working
control overall gain.

rgds, sreten.

[bmwman91]

I am having a similar problem. I am running 3 A500's in a tri-amped setup with a mono sub. The amp that drives the sub operates in bridged mono mode. Using either XLR or TRS inputs, the output will cut out intermittently, or get very weak. I keep having to reach back there & wiggle the input plug. Since it happens with two different inputs, I don't think it is the physical connector.

It seems like a few folks have run into similar things. Is it pretty simple to check the input caps & opamps?

Thanks!

[sakis]

havent seen much of those failed .... before looking for sophisticated and extensive tests check the obvious .... for example condition of the switch that controls bridge functions on the back ...and also the condition of the plugs that wire the back board with the main boards

that could be an issue ... also look for obvious damages like burned resistors and missing voltages

regards sakis