yamaha g100 1x12 version 3, amp issue - no sound (sometimes)

[mentalmidget]

hi, I bought used yamaha g100 1x12 version 3. sounds great when it works. im having a few issues :

- sometimes, when turning on the amp (it lights up) it either takes a couple mins to start producing sound, or not at all. it'll stay dead silent, then a clicking noise will occur and then its able to start making noise..
- sometimes (usually) it starts producing sound instantly.
- just now, i played for about 5 mins, no issues at first, and then it went silent again. now when i try and turn it on right after, it wont produce sound. this happened before, its like i had to wait a day or at least a few for it to start working again.

not an amp tech at all. no idea what this could be. its like its a loss of power to the preamp section.

https://imgur.com/gallery/yamaha-g100-112-iii-krQQ02U

any tips?

it's an incredible amp. want to fix it.

[Kaz Kylheku]

The flow of signal through an amp is pretty linear, like a factory assembly line. All of the blocks in the line have to pass signal, or else there is no sound. A no-sound-at-all problem could be anywhere.

If the amp starts passing signal without you banging on it, it looks strongly like a thermal issue. Somewhere there is a bad contact: some kind of mechanical hookup, or a cracked solder joint, or a bad circuit board trace, where a slight thermal expansion improves the contact.

One form of contact that is common in amps is the contact between a potentiometer wiper and the resistive track. Amps have multiple level controls at various gain stages, and if any of those lose contact due to oxidation or contamination, then you get no signal. Next time you fire it up, give every single knob a good spin.

Input jacks can be intermittent, and same with speaker hookups.

Are you able to switch channels? Are both dead at the same time? If so, the problem is in whatever is common between the two: any common preamp path and power amp.

Tapping on things with the eraser end of a pencil can help find a problem like this. Like when the amp is working, and you tap on a certain component and there is a loud crackle or outright relapse into nonworking, then you almost certainly found the culprit. Or vice versa, when it's not working, if tapping on something gets it to work or at least produces a noise.