Please help with Repairing my Ampeg BA115!
Hello all, ive bought a Ampeg BA115 three years ago and i was jamming at 60% volume for 30-45 minutes last week and all of a sudden my audio cuts out. Ive driven this amp at max volume for over 3 hours on a hot summer day so i don't think heat was the issue. It is the BA115a i think, the 100-watt solid state combo, so its not the newer ones with the preamp tube for those who may not be familiar with the BA series.
My brother has extensive electronics training, but nothing in the way of amplifiers and audio components.
I will list some of the things we have done and tried already.
1.We replaced the two MOSFETS in the "power stage" i believe he said, an OP-AMP integrated circuit chip that we saw some smoke come from, and also a resistor that started smoking. I can get the exact part numbers and values for the parts if need be, but there all generally in the same area.
2.We used an oscilloscope to see if the signal (a guitar cable with a 1/4-1/8 adapter hooked up to an ipod) we were feeding it was going through and it seemed to be modulating right. But we still get no sound to come out of the speaker.
3.Tested some other parts, the Transformer is putting out all the right voltages, and the speaker is fine, and the filter caps are good. I believe the DC Rectifier was also good. Oh and yes, the fuse is good as we have other 2.5 amp fuses laying around.
This thing is like my baby and i don't have the money to get a whole new amp. Any suggestions would be greatly appreciated, we're running out of ideas on what to test. Besides seeing smoke come out of that OP-AMP and the discolored resistor, everything else looks all new and shiny.
Please if there's any other information you need that might help you with helping me, please let me know, i'm pretty much begging here!