As far as I see you do this professionaly, mainly speaker, so why don't you get a cheap scope, like a two channel digital from Reichelt for €130?
You would be done with fault analysing in a few minutes and learn something about it. Just soldering around and try, by chance, to find a defective part, is not the way to do it. Not even if you do it for sale on eBay only. Even if you find a blown transistor, it may not be the only part in a chain of amplification.
Also, use a current limiter (simple light bulb) in line to the mains, so you can see excessive current flow. You got a lot of valueable information here, maybe use it?
https://www.reichelt.de/digital-spe...yJdTnt-LgGA3JI3S-bPvUtogIUH2B2SRoCUpcQAvD_BwE
You would be done with fault analysing in a few minutes and learn something about it. Just soldering around and try, by chance, to find a defective part, is not the way to do it. Not even if you do it for sale on eBay only. Even if you find a blown transistor, it may not be the only part in a chain of amplification.
Also, use a current limiter (simple light bulb) in line to the mains, so you can see excessive current flow. You got a lot of valueable information here, maybe use it?
https://www.reichelt.de/digital-spe...yJdTnt-LgGA3JI3S-bPvUtogIUH2B2SRoCUpcQAvD_BwE