Eton MA 750.1

I have a Sub amp, with burned resistors. The owner mixed positive an negative , so the remote circuit was burned. Thats allready fixed. But on the preamp board are two resistors burned, and i can not recognize the value. The amp play disorted, if i connect an input from my home amp, i have strong ground noise. Also the output, if i connect a signal generator, i have strong disorted signal. Maybe somebody can give me the values?
I tried already a value, but that's wrong.


  • IMG_20191117_124455.jpg
    647.8 KB · Views: 60
  • IMG_20191117_124513.jpg
    690.3 KB · Views: 58
  • IMG_20191117_124525.jpg
    390.1 KB · Views: 59
Still working on this amp. Maybe someone can calculate r 815. See diagram attached.

The sinewave on this amp is changing the amplitude. Makes strange noise. I think this is a feedback circuit, op amp jrc 062 controlling the positive and the negative half of the sine.


  • IMG_20200220_094200.jpg
    653 KB · Views: 30
  • IMG_20200220_094205.jpg
    218.4 KB · Views: 36
The resistor in the photo at r815 is 22k. He may have put that resistor in place thinking that’s what went there, not knowing for sure because he stated the original resistor was burned. At least, that what I assumed.

The resistor at r811 is 220k.

Since he is dealing with the inverting and non inverting outputs of the op amp I would think you would want them to be balanced since the circuit is the same for both outputs.

I figured that was the reason he was getting the distortion. I would think if he looked at it with a two channel Oscope he would have seen an unbalanced sine wave or square wave.