UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Rotel RX402 soft put-put

paulsherwin · 2nd Dec 2019, 2:40 pm

I agree that this is unlikely to be a transistor fault, and it does sound like some sort of stability issue. It will help a lot if you can identify the section of circuit which is responsible. There appears to be some interaction with the volume control rather than the control simply acting as a variable attenuator, so look very closely at things around there. Double check you have fitted any replacement electrolytics the right way round.

If the symptoms are identical on both channels, that normally points to some sort of PSU issue.

Do you have a scope? If so, look for anything strange on the power rails.

2nd Dec 2019, 2:40 pm	#4
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,970	Re: Rotel RX402 soft put-put I agree that this is unlikely to be a transistor fault, and it does sound like some sort of stability issue. It will help a lot if you can identify the section of circuit which is responsible. There appears to be some interaction with the volume control rather than the control simply acting as a variable attenuator, so look very closely at things around there. Double check you have fitted any replacement electrolytics the right way round. If the symptoms are identical on both channels, that normally points to some sort of PSU issue. Do you have a scope? If so, look for anything strange on the power rails.