Guitar amp dies then comes back to life after turning power on

I have a carlsbro amp that for the last few years will play for a few minutes and then die on me. I turn the power off and then turn power on a few seconds later and it will work. This cycle continues for a while and then not even turning the power button works anymore. The amp has hardly been used. Anyone know what is wrong with it. Attachment 280386

I'm no amp expert, far from it. But try playing 'Smoke On The Water', that should fix it ;)

sounds like a heat issue to me.
could be a dodgy cap.
The music shop at Knox has a good repair guy.

Thanks fly, might try that but i put some contact cleaner into some of the input jacks and the amp didn't cut out after an hour so not sure what to make of it.

does sound like heat contraction expansion issue
when it cuts out does the power indicator light go out as well?

some PCB based amps can be a real can of worms and some techs wont touch em

try researching the issue with the model of your amp - could be common

:whs:

If contact cleaner seems to have done the job, then it'd be worth your while to pull that PCB and thoroughly checking for dry or broken solder joints where the jack pins meet the PCB pads... poorly soldered joints there can literally break simply from the jack flexing when leads are plugged/removed.

While you have the PCB out it's also worthwhile to check any nearby joints on the PCB, 'cos the c/cleaner might've had a bit of "overspray" thru the jack into nearby parts of the PCB and thus temporarily fixed the problem joint.

If you do find any problematic joints, it's usually a straight forward matter to resolder 'em; I recommend using a wick to remove the old solder and NOT just throwing on a bit of flux and applying heat to the old solder, unless you like pulling PCBs in and out on a regular basis. ;)

The contact cleaner may have temporarily cooled the hot spot

Quote:

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Originally Posted by old_picker

does sound like heat contraction expansion issue
when it cuts out does the power indicator light go out as well?

some PCB based amps can be a real can of worms and some techs wont touch em

try researching the issue with the model of your amp - could be common

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Thanks guys for your responses. Power light doesn't go out, you'll be playing and then the sound just dies out. Haven't found much on this particular amp in the research I have done. It's a solid state amp, how hard are the PCBs to take out?

Sounds like cleaning contacts may be the way to go

Carlsbro Cobra 90 - diyAudio

I had a similar problem with a bass amp once - it was the effects loop too.

Thanks Peter.

Those little solid state amps often have a Power Amp IC that can generate enough heat to 'de-solder' itself.
The solder joints become 'dry' or cracked & sometimes they connect & sometimes they don't.
Easy fix if you have a soldering iron & know where to look.

Quote:

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Originally Posted by Cliff Rogers

Those little solid state amps often have a Power Amp IC that can generate enough heat to 'de-solder' itself.
The solder joints become 'dry' or cracked & sometimes they connect & sometimes they don't.
Easy fix if you have a soldering iron & know where to look.

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Thanks Cliff, half way there, ie have soldering iron not entirely sure where to look though.

Look for any IC's with (hopefully) big heat sinks... ;)

Thanks Skew, that brings me a step closer.