Behringer ep 1500 little sound

Hi guys, new to the forum so bare with me

im looking for some help with a behringer ep1500 that I got my hands on. it powers up, fans work etc. The problem is with the gains up full the sound is only just audible from each channel. The problem in my eyes has tp be something before the power amps? something that both channels have in common. my experience with fixing electronics is limited to dry joints and visibly blown parts (swolen caps/ burn marks around resistors etc)

I could really use some help with where to start looking and what to test. I've had a poke around for bad joints etc with a wooden chopstick. checked the ribbon cable but no luck. any help would be much appreciated guys

Check the rail voltages on the power amp. Should be coming off main filter caps to output transistors.

iampoor1 said:

Check the rail voltages on the power amp. Should be coming off main filter caps to output transistors.

Click to expand...

Thanks for the reply. by main filter caps I assume you mean the 4 big capacitors that are on the same board as the transistors? what voltage should it read?

You can find the schematics over here: https://www.electronica-pt.com/esquema/audio/behringer-audio/behringer-ep1500-revf-16016/

Or if you prefer the more complete documentation of where Behringer... umm... "got their inspiration"...  :
http://schems.com/bmampscom/qsc/QSC_RMX_Service_Manual.pdf

Make sure the DIP switch is set correctly, set to Bridge mode off, and connect speakers to the banana jacks.  It could be as simple as that, I have encountered that before. You can also inject signal into the power amp to test for function if you don't have an o-scope.

is that a speakon cable output? sometimes people use different pins for the output,


hopefully that model does not have the output devices buried under a heatsink and pc board, those things are priced to be landfill upon failure, 

The layout would appear to be serviceable enough..?

https://medias.audiofanzine.com/images/normal/behringer-europower-ep1500-782562.jpg

pull the output transistors, measure hfe, if ok, pull the drivers and pre drivers, check hfe, if ok, you have possibly an opamp or short protection circuit problem.

The common fault for power amps is failed output devices (typically shorted collector emitter), but such failures generally blow fuses of trip circuit breakers so not a soft failure.

You may have something cheaper to fix, like a bad jack or solder connection.

JR