SQ80 Overheating

#1

So the power supply on my SQ80 has been overheating. After a while the whole keyboard will lock up with no response to either the keys or panel buttons/sliders. If I restart it, it will work for a short time before overheating again, and the overall time it takes to lock up depends on the ambient air temperature. During the summer it takes about twenty minutes, during the winter it rarely happens.

I already intend to replace the original EL caps on the PSU so that the voltage regulators don’t have to work as hard, but I was also considering replacing the regulators themselves as well as the thermal compound between them and the heat sink. Has anyone else tried this on the SQ80 or another board? Will something like arctic silver or mx-4 CPU thermal compound work? Any other suggestions for overheating issues?

I’ve considered attaching some small fans to the heat sink as well, but that’s a last-resort scenario.

#2

If you can borrow a thermal imaging camera (highly recommended for circuit diagnosis) then you can see what is causing all the heat.

Linear voltage regulators emit excess input voltage as heat, so it may be they’re getting too much input voltage. The thermal compound may be on too think or have dried out, but I don’t think that’s the issue.

You can replace the regulators for switch mode regulators, these don’t emit heat but you have to some at high switching rate to avoid noise. Probably not recommended for a synth with so much analogue circuity.

#3

That’s a cool idea, to use a thermal imaging camera!

#4

It’s a common approach for spotting bad RAM chips on old 8-bit micros. In a row of identical chips the bad one usually glows.

I imagine it would work on analogue synths with rows of identical voice chips or transistors.

A low tech option is to use an IR thermometer.

#5

Thanks for the advice! Unfortunately, the low-tech option may be what I have to go to for the time being, short of just outright replacing everything. I can’t think of anyone in my area that would even HAVE an IR camera, let alone would let me borrow or even rent it.

#6

Camera is about £300 to buy, depending on model. But an IR thermometer will give you a temp reading without making contact. Those are £10 tops.