
A friend had an SC120 that was making all sorts of noise and misbehaving. First notable thing was one of the 6(!!!) EL34s was redplating and was for the bin.

When I pulled the chassis I was greeted by this. Yup, the safety ground and become disconnected, leaving the amp at risk of causing electric shock should there be a short to the chassis and also leaving the circuit floating.

I repaired the safety ground and also added some much needed strain relief with a couple of cable ties behind the cable gland.

I stuck a spare EL34 in and rebiased to around 60%. Ideally I'd want to stick a full fresh set in but that's not an option for my friend right now. The spare I have is matching okay with whats in and the quiescent current on each half of the output transformer is reasonable balanced.
The amp is sat idling for an hour on my bench to test it. I can't crank it right now unfortunately. So far no bad noises or redplating.
The big blue cap in the top of the photo was also secured into the clamp as it had become loose.
I should hopefully be able to drop this back with my friend soon. It'll get cranked of course.