Hi everyone,
Something weird happened to my Thorens TD-125, MK1, second board (with one rectifier).
After playing some singles at 45rpm my girlfriend thought she turned the player off but actually set it to 16rpm. The light went out so she thought it was off and it stopped turning.
When I got home I noticed a weird smell and after some searching discovered it was coming from the TD-125. I unplugged it and noticed the metal parts and motorplate were all very warm/hot.
The next day I tested it and 33rpm and 45rpm were kind of working but 16rpm didn't and you could feel it getting warm immediately.
It took the motor assembly to my workshop and recapped the pcb. Now everything is kind of working but there are some problems. The switching of speeds is erratic. Sometimes the motor makes a buzz, and sometimes it turns backwards.
I hooked it up to a scope and noticed the red wire sine-wave was very unstable and dancing all over the place. The blue wire was kind of stable but also showed some fluctuation.
When I disconnect the motor and check the sine-waves they are clean and stable; connecting the motor again makes them unstable.
Is my motor broken? Or is it the power transistors? Any other suggestions?
Something weird happened to my Thorens TD-125, MK1, second board (with one rectifier).
After playing some singles at 45rpm my girlfriend thought she turned the player off but actually set it to 16rpm. The light went out so she thought it was off and it stopped turning.
When I got home I noticed a weird smell and after some searching discovered it was coming from the TD-125. I unplugged it and noticed the metal parts and motorplate were all very warm/hot.
The next day I tested it and 33rpm and 45rpm were kind of working but 16rpm didn't and you could feel it getting warm immediately.
It took the motor assembly to my workshop and recapped the pcb. Now everything is kind of working but there are some problems. The switching of speeds is erratic. Sometimes the motor makes a buzz, and sometimes it turns backwards.
I hooked it up to a scope and noticed the red wire sine-wave was very unstable and dancing all over the place. The blue wire was kind of stable but also showed some fluctuation.
When I disconnect the motor and check the sine-waves they are clean and stable; connecting the motor again makes them unstable.
Is my motor broken? Or is it the power transistors? Any other suggestions?
I tend to think analyse your parts changes first. Did you keep the old parts ? Pictures will help.
Yes, I still have the old parts but they look ok in that there is nothing visible. Also the unstable frequency occurs at all speeds and only when I connect the motor.
I replaced all electrolytic capacitors and some of the film capacitors. I can take pictures tomorrow.
I replaced all electrolytic capacitors and some of the film capacitors. I can take pictures tomorrow.
Apparently the caps to be suspicious of would be C4 and C6, did you swap those?
Otherwise I would direct my attention to the motor's bearings. How easily does it turn? If it was hot for an extended time the lubricant may have gummed up.
Otherwise I would direct my attention to the motor's bearings. How easily does it turn? If it was hot for an extended time the lubricant may have gummed up.
I replaced electrolytics C2,3,4,5,6 and filmcap C7 and C9. The motor is turning smoothly. But just in the wrong direction sometimes and it also makes noise sometimes.
But the weird thing is that there's not really a logic pattern in when and why it happens. It's pretty random. Something is messing with the sine-waves as soon as I connect the motor.
But the weird thing is that there's not really a logic pattern in when and why it happens. It's pretty random. Something is messing with the sine-waves as soon as I connect the motor.
What do the signals at the bases of the power transistors look like? What does the signal at the collector of T3 look like?