Quote Originally Posted by dimkasta View Post
OK feel free to call me a moron...

A while back I changed C210 to 550nF following some random "mod" advice I found somewhere.

I changed it back to 220nF and the tt is rotating normally once again

I will leave it running for a couple of hours on my bench to see how it behaves and then try to have a listen

Co&
Do you still have D301 installed? I remember reading somewhere it can overheat and create issues.

I also remember reading a suggestion to put a small heatsink on 6680.

On the regs part, I would check the datasheets to see what the chips like to see on their output. There might be an oscillation that is slowly heating up a reg, pushing it to its overheating protection zone. Such temperature should be easy to feel with your fingers if you do not have a DMM with a thermocouple.
Great you got it fixed!

D301 is still in, it could be the source of excessive noise. If time permits it will be replaced by a LM431 low noise zener.

I think C217 also may be causing troubles since the C209 (100uF) already has very low ESR. If this doesn't work out I will move the cap to the pins on the 6680.

The CCS in place of R201 gets way too hot for its dissipation. Oscillation may be at order but there is already an extra 100R resistor between the CCS and the 6680 that should damp this. Replacing that one too for a new one I tested at the desired current and dissipation. This new CCS doesn't even nearly get as hot.

Temperature of all big chips seems ok (lukewarm).