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?
As as_audio mentions, one phase may be out. If it is a 3phase motor and one phase is out, could go backwards. Buzzing I think too could happen. I've no idea if the TD is a 3 phase though.
As I mentioned both sine-waves are stable and clean without the motor attached. As soon as I hook up the motor things get fishy and unstable.
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The motor has three wires, two phase, the second phase is via switchable electrolytic capacitors for three speeds, so the cap for 16 rpm may be defective or wired backwards (post 1). Let us stop speculation until we see the facts, pictures etc. If you say the drive voltages are "fishy" you probably even have scope pictures.
Speed setting doesn't matter. It occurs at all speeds. But will get back to this later after June 15.
Post 1 : "33rpm and 45rpm were kind of working but 16rpm didn't".
Post 12 : "Speed setting doesn't matter"
Post 10 : "As I mentioned both sine-waves are stable and clean"
Do not expect to see a waveform on output "red" without motor connected ..
Post 12 : "Speed setting doesn't matter"
Post 10 : "As I mentioned both sine-waves are stable and clean"
Do not expect to see a waveform on output "red" without motor connected ..
Post 1 : "33rpm and 45rpm were kind of working but 16rpm didn't".
This was before I recapped the pcb as stated the next line:
Post 1 : "It (sic, oops) took the motor assembly to my workshop and recapped the pcb."
The "kind of working" meant that the motor was spinning at 33 and 45rpm... 16 rpm was dead. After recapping 16rpm rotated again. But sometimes all three speeds hicupped (delayed start) and sometimes they started backwards.
This was before I recapped the pcb as stated the next line:
Post 1 : "It (sic, oops) took the motor assembly to my workshop and recapped the pcb."
The "kind of working" meant that the motor was spinning at 33 and 45rpm... 16 rpm was dead. After recapping 16rpm rotated again. But sometimes all three speeds hicupped (delayed start) and sometimes they started backwards.
Sorry missed the mention of both clean. But I'd expect a sine wave on all 3 wires. There is no gnd on the type of motor I am thinking of. Think of like a 3 phase transformer where all 3 wires are hot and basically no current flows to gnd if it is balanced. Is the 3rd wire connected to gnd or a signal? I've been putzing with a ECM fan motor for almost a year now and there is no gnd. Just 3 hot phases 120 degrees out of phase with each other. I've had some weird stuff happen when I don't hook up all 3 wires correctly. And switching 2 wires reverses the motor.
The Thoren's TD-125 drive consists of a power Wein bridge oscillator and a synchronous motor. The oscillator is connected to one winding of the motor and a phase shift network that goes to a second winding of the motor. Synchronous motors will run in either direction so the phase shift network is to make sure the motor always runs in the correct direction. If the motor runs in the wrong direction make sure the phase shift network is connected correctly.