Behringer ULTRATONE K900FX PA/ Keyboard Amp

[Wonker]

I’m having issues with a Behringer ULTRATONE K900FX

The Amp powers up but the LED’s on the EQ don’t light up. I have no output from any of the three channels. Everything on all 3 the boards, the crossover and all wiring look good. I tested the speaker with another amp and it works.

I tried to test the amp with headphones and I got loud popping when putting the ¼ headphone plug in.

I power the amp down and it acts like tube amp powering down and the EQ LED’s light up.


I want to cry

[Enzo]

SOunds to me like you have lost one of the power supply voltages. Specifically one of the +/-15v supplies for the preamp. Look on the powr amp module for the two 15v regulators - 7815 and 7915. See if both are making 15v.

[Wonker]

Ok I'll do that

I also just found that one of the two 3300uF 35V Caps has a odd dent in its side and has a little bit of burnt brown crap around it.

[Wonker]

Look on the powr amp module for the two 15v regulators - 7815 and 7915.

To a rookie what do these look like? These are the black square three legged looking things right?

[Enzo]

They look like this: