TD125 motor stopping

[MrMark]

A new issue has developed today with my Thorens TD125 MKii. The motor has twice stopped turning. the strobe light is still on, so ther is till power to it, but no spin on motor. If I change the speed to 45 (or 16) and back to 33, it spins again. The previous owner says the switches need cleaning and that it does not sound like a failing electronics issue and I thought i'd get other opinions on what the problem might be here.

And also perhaps clues as to how to get near the switch to clean it, and if my 100% strength liquid deoxit is appropriate, as i think it is...

thanks (again, you are a helpful community indeed)
cheers, Mark

 

[dr*audio]

It could indeed be the speed switch or motor switch. It could also be the speed control. Yes, De-Oxit should clean it. go to Vinyl Engine and download the service manual (free) and it will tell how to disassemble it. It's been so long I don't remember if those flat knobs just pull off or not.

 

[ehoove]

You may also have a component failure in the Speed control board. Just because the Strobe light lights, does not mean the motor does not have an issue as well. I have a service manual if you need a copy.
Regards,
Jim

 

[MrMark]

You may also have a component failure in the Speed control board. Just because the Strobe light lights, does not mean the motor does not have an issue as well. I have a service manual if you need a copy.
Regards,
Jim

I guess I am somewhat hopeful, in that it is intermittent, that it is just a cleaning it needs... fingers crossed!

 

[JonL]

I went through the circuit on my TD-125 MkI, and replaced all the electrolytic caps and some of the small-signal transistors. The service manual had good instructions for measuring voltages and setting the trimpots. When I couldn't get the right voltages, I made an educated guess about the transistors and solved my problem. I think the MkII has a significantly different motor control circuit (I think that's the biggest difference between MkI and MkII, other than tonearms), but if the MkII has electrolytic caps in the circuit, I'd think about replacing them.

 

[MrMark]

I went through the circuit on my TD-125 MkI, and replaced all the electrolytic caps and some of the small-signal transistors. The service manual had good instructions for measuring voltages and setting the trimpots. When I couldn't get the right voltages, I made an educated guess about the transistors and solved my problem. I think the MkII has a significantly different motor control circuit (I think that's the biggest difference between MkI and MkII, other than tonearms), but if the MkII has electrolytic caps in the circuit, I'd think about replacing them.

What were the symptoms that made you need to replace that stuff?

 

[ehoove]

If moving the switch solves it, I would have to say dirty switch. My bad for missing that detail. The selector should be reached from inside the table, however removing the slider pad should allow a shot of deoxit to the switch.But first turn the table off and move the switch with vigor to see if friction cleans the contacts first.
Regards,
Jim
Great table BTW!

 

[MrMark]

If moving the switch solves it, I would have to say dirty switch. My bad for missing that detail. The selector should be reached from inside the table, however removing the slider pad should allow a shot of deoxit to the switch.But first turn the table off and move the switch with vigor to see if friction cleans the contacts first.
Regards,
Jim
Great table BTW!

Yes, I really like its looks and build quality. Beats the pants of the TD160 it replaces! I have tried removing the slider pads, but am leery of damaging something (though that table seems you could drive a truck over it and still have it work just fine!) Do the just pry off or some such thing?

Thanks for all the suggestions by the way.. very helpful bunch!

 

[JonL]

What were the symptoms that made you need to replace that stuff?

I bought the table in rough shape and it had been sitting unused for years. In the course of restoring it I felt it prudent to replace all the electrolytic capacitors. I also found instructions (apparently originally Thorens factory sanctioned) for converting the useless 16 RPM speed to a less useless 78 RPM setting. That modification involved changing one of the electrolytic capacitor values as well as two of the film capacitors. Then, in checking the voltages as part of the speed calibration process, I found that I couldn't get two of the voltages to come into spec even if the associated trimpot was hard over to one side. I studied the schematic, and with a tiny bit of electronics knowledge, a bit more logic, and a lot more luck decided upon the small signal transistors as the likely cause. I tracked down suitable replacements (the original numbers were obsolete, but I found some obscure cross reference on Google) and after installing them I was able to dial in all the right voltages and get my speed pots set correctly.

I think the MkII circuitry is simpler.

 

[JonL]

I don't recall how the sliders come off. I'm thinking they are screwed on from the underside but I wouldn't swear to it. I'll have a look at mine and see if I can remember.

 

[MrMark]

I don't recall how the sliders come off. I'm thinking they are screwed on from the underside but I wouldn't swear to it. I'll have a look at mine and see if I can remember.

Thats all pretty cool in any case I am hoping to not have to remove the subchassis as the suspension is set pretty well and that takes some time! If i need too I need to... In the mean time i am hoping vigorously moving the switches cleans them up enough that the problem stops for now and I can worry about it in a few months or better yet years...

 

[jbpollock]

A new issue has developed today with my Thorens TD125 MKii. The motor has twice stopped turning. the strobe light is still on, so ther is till power to it, but no spin on motor. If I change the speed to 45 (or 16) and back to 33, it spins again. The previous owner says the switches need cleaning and that it does not sound like a failing electronics issue and I thought i'd get other opinions on what the problem might be here.

And also perhaps clues as to how to get near the switch to clean it, and if my 100% strength liquid deoxit is appropriate, as i think it is...

thanks (again, you are a helpful community indeed)
cheers, Mark

I had a similar problem with my Mk I and it was solved by replacing the electrolytic caps. I replaced 3 - one for each speed.

 

[dr*audio]

Yes, I really like its looks and build quality. Beats the pants of the TD160 it replaces! I have tried removing the slider pads, but am leery of damaging something (though that table seems you could drive a truck over it and still have it work just fine!) Do the just pry off or some such thing?

Thanks for all the suggestions by the way.. very helpful bunch!

As I said, if you download the service manual, it will tell you how it comes apart.

 

[JonL]

As I said, if you download the service manual, it will tell you how it comes apart.

+1.
The tables are heavy and awkward to lift and position to do the work, but after that they are very easy to work on. They used really nice hardware and designed the unit to make it very serviceable. They even use captive screws in many locations where it helps with assembly.

 

[Blue Shadow]

I just did the 'upgrade' on a friends TD-125 II. I moved to the 8-pin chips and swapped all the parts in the lists above, as well as the C1 cap on the input board. Dialing it in, the SM makes it hard to ID the test points and which of the 9 VR should be adjusted for each step. Vinylengine had this info in pictures along with the instructions from the manual on one page. Here is the link to that:
http://www.vinylengine.com/turntable_forum/viewtopic.php?f=17&t=50096

The unit works much better now. I'm going to let it burn in for a bit and redo the adjustments as specified after the final three, setting the speed control in the center and making that correct. Thanks @tnsilver for this 'how-to'.