This may be a machine from the late '70s' but it has served me well - 'til now!
Both speed adjusters seem to have died and the turntable varies fast and slow of its own free will now.
Anyone know of somewhere that may be able to sort this out. I don't really want to junk it
if it can be saved! Thanks

I've never seen that particular model, but direct drive TT's are generally a brushless DC motor as part of a servo loop.

So there's got to be some kind of feedback system that detects the rotation speed and feeds it to the electronics, the electronics compares the feedback signal to the speed you've selected, and controls the motor speed to make them match.

If the feedback is missing the TT will probably 'hunt about' and not maintain any kind of stable speed.

Assuming the feedback is external to the motor (and it could be internal) you might be able to spot something broken? (hence the reason for this explanation).

Thanks for that, I took the base off but as you say it's just a set of electronic circuits, so there's no indication of what may have failed.

If you are so inclined there is a service manual here

http://www.kallhovde.com/pioneer/tri..._ART-182-0.pdf

It has full circuit diagrams of the drive electronics. One thing I would check first are the connections to the speed selector switch and the variable speed control pots. And also check out the condition of switch and pots.

After several decades I would not be at all surprised to find them in need of a bit of TLC. If not outright replacement. You might find that a bit of contact cleaner sprayed into the switch and pots may cure the problem.

Though I have seen carbon track pots where the track has worn out so badly no amount of spray will ever get them back into life. But you could be lucky and it's just 40+ years of gunge build up.

Thanks chrisjr, Servicing will be beyond me but I'll try some magic spray and see what happens! As you say after 40 years things will be a bit tired.