Tube amp noise at start up

I bought a Fender Tweed Blues Junior IV Ltd Edition brand new a few years ago. Never left the house and rarely played.

Recently fired it up and there was a lot of crackle, then verged on feedback, then went quiet and played normally.

I'm cycling it a few times, letting it cool, the restarting. Can I expect the crackling to diminish with more frequent use?

It is very quiet (as to extraneous noise) and sounds great as soon as the start up trauma passes.

Per suggestions, I have carefully pulled out & reinstalled each tube & I have run all the knobs back & forth multiple times.
More detail. After about 3 - 4 seconds of crackle, a feedback loop starts and crescendos in another 5-10 seconds, then quiet and the amp works normally with no background noise. Any idea on the feedback? I've made sure I had the amp freestanding and not backed up against a wall or corner.

All the above happens with ALL the knobs at usual settings (mid range) OR zero'd out at turn on.

Sounds like your tube sockets need retentioning (using a thin sharp probe to close off the tube socket pin receptors). The fact you hear crackling until it warms up indicates the pin tube receptors are spread open to far and with heat making better contact when the amp heats up.

My money's on a marginal solder joint on the PCB or a ribbon connector that's partially unseated.

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Originally Posted by phantomman

My money's on a marginal solder joint on the PCB or a ribbon connector that's partially unseated.

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Yes, that is also a possibility and what I would say to check first.
I am used to point to point wiring tube amp but yeah, if it has a printed circuit board those would be the first choice. Good Call!

Would turn out the lights and watch what the tubes do at power on.

IIRC that amp has a standby, so does it do it in standby or just when you take it off standby?


Chuck

I agree with Phantomman, too many times a poor solder connection has been the problem on the BJ, and Hot Rod amps. I don't use "lead free" solder for repairs!

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Originally Posted by Bill Moore

I don't use "lead free" solder for repairs!

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Are you worried that young ghetto kids or fascists from the EPA would lick those solder joints?

:lmao:

Lead free solder is "brittle", it takes more heat to melt, and 60/40 flows easier. I think a lot of the poor connection/cracked solder joints are due to lead free use.

I would simply move the tubes around in their sockets a little and make sure they're reset firmly in place. Probably all you need to do.

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Originally Posted by Tele-Bob

I would simply move the tubes around in their sockets a little and make sure they're reset firmly in place. Probably all you need to do.

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Agreed. "Never left the house and rarely played" is the key here. Tube amps don't usually fair too well being parked and not used. They need a jostling once in a while to keep them happy.

Chuck