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Acoustic 450 solid state guitar/bass head repair help

2020 Views 22 Replies 8 Participants Last post by  jb welder
Hi all! Turning the amplifier on and plugging in greets you with you its signature wall of sound, no issues. But after playing for around 10mins, the volume cuts off drastically to a quarter of the original level and distorts the signal in a guttural choked out way. The most solid bit of evidence I have of a cause to the problem is that it worked fine until I was playing it during a mild storm. There was a power surge that tripped the breaker for the outlet I was using, after that session the problem has persisted.

This heavily screams "overheating" to me, supported by how taking the board out of the enclosure makes normal volume last longer and when adding a fan it can last indefinitely. I've tested the mammoth power supply smoothing capacitor and it reads what it should and have desoldered/tested the other polarized caps. None of them read lower than the rated value, but some of them much higher for some reason. There was a 4.7uF coming in at 7.3uF, would having higher cap values be an issue?

I haven't seen any cracks in the tracers or otherwise burnt/swollen components, but i agree that there might be a spot on the board that has need of more solder. As the components heat up a short might develop? Maybe the input or output jack to the speaker? Has anyone had a similar problem with a solid state amp? I'm looking for advice on what to try next.

Thanks in advance!
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Following this. I have a 450 and now a 470. Never heard of this type of problem.

When I use my 450, its for 5 to 6 hrs straight at min half volume ( very loud drummer... ) and never had a hitch except blown speakers.
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