Cambrigdge A500 amplifier troubleshooting

[omnitek]

Hi,

I need some help to troubleshoot this Cambridge A500 amplifier that had some blown output darlington SAP15P and SAP15N transistors in the left channel. I replaced them and the driver and pre-driver transistors as well. There was also one burned resistor that I replaced.

I was able to adjust the bias properly but when I put a load at the output and a sine wave at the input, I see some sort of oscillation or distortion on the negative peak when I check the output with an oscilloscope. The distortion or oscillation is there even with a low signal on 1 volts at the output. It is not present when I remove the load from the output.

I checked for other bad resistiors, diodes or capacitor but couldn't find one.

Any help would be greatly appreciated.
Thank you!
Regards,

Nicolas