Hello everyone. I usually find a strange thing in this speed control card of an EMT turntable.
When in Stop, if the circuit is cold, the motor rotates slightly. The mechanical brake stops the engine, but sometimes it can slip and the force of the engine overcomes the brake. After a few minutes pass, the electronics increase the temperature and the anomaly disappears.
I think the thing appears in the last exit stage. When hot there is 0v, but when cold it can exceed 1v.
Any suggestions?
No experience with this particular model but it's very common that low value (0.1 - 10μF) electrolytic capacitors cause trouble in servo controlled turntables.
It may be worth checking the lot but if you must start somewhere start with the 1μF ones.
All electrolytic capacitors have been replaced.
It seems like a characteristic of the design. A blast of air and a brake that slips cold makes the engine move slightly for a few minutes.
I would like to improve that situation.
I have a Marantz SD9000 that had a bug in the circuit that had a fluctuating playback speed, could not get a steady rpm out of the motor. I chased that off and on for over a year. It turned out to be a dirty switch that either supplied the power or ground, can't remember. So, trace the supply lines to it and see if they run through any switches...
Now I think it's not a temperature problem, it's because of the humidity.