RUB1.1600D Soundstream

[Hexhclass]

Owner told me this amp is not as powerful as it was a week ago. The amp plays good audio but when I start to crank it up it sound like I am running it off a 7 amp power supply although I have it hook up to a 32 amp supply.
Input voltage stays above 12v while testing.

Any have come across a problem like that?

 

[Perry Babin]

Look at the amplitude of the primary and secondary waveforms. Are they both collapsing or both staying about the same?

Is the rail voltage dropping?

Are the tops and bottoms of the audio clipping at the same amplitude?

 

[Hexhclass]

Where in the circuit do I have to check for the primary and secondary waveforms?

 

[Perry Babin]

On the transformer windings.

 

[Hexhclass]

Fix

Not sure what fix it but the rail voltage was dropping all the way to 17v-+
I found kia431 shorted.I replace it along with the rail caps because i have seen lots of amps with similar board that had bad rail caps.

 

[Perry Babin]

Sometimes I think the rail caps fail because the voltage goes too high. In at least some of the amps, the 150k ohm resistor near the 431 goes out of tolerance (high) and allows the rail voltage to go high.