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How to- Thorens TD-145 Auto Stop?

garpt

garpt

"Analog is BACK!"
Hi
Anyone know how to adjust the auto shutoff position on a Thorens TD-145?
The arm is raising and powering off before the end of the record. It is a N.O.S., never used before, but something must have been knocked out of calibration during shipping.

I hope its something I can do, I just paid for a lubrication, but there was no cartridge installed so I guess this wasn't checked.

Thanks!
 
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The position of the unit on the base of the tonearm that has the antiskating dial has to be at the correct angle.To move it you need to loosen the two allen screws that you would loosen to adjust the VTA.
 
garpt said:
Hi
Anyone know how to adjust the auto shutoff position on a Thorens TD-145?
The arm is raising and powering off before the end of the record. It is a N.O.S., never used before, but something must have been knocked out of calibration during shipping.

I hope its something I can do, I just paid for a lubrication, but there was no cartridge installed so I guess this wasn't checked.

Thanks!
Click to expand...

The service manual is on the VE forum. But well, the answer is as follows: Under the tonearm there is a magnet which turns with the tonearm. This magnet, at the end of the record, positions itself over a coil and that's what trips the stop mechanism.

There is a screw that allows you to move the magnet position so it shut offs exactly at the end of the record.

(You need to disassemble the turntable's bottom cover and then the tonearm's cover/shield to access this).
 
Appreciate it all!
so, it's definitely user- servicable for a fairly competent person. It sounds like a really unique and clever system for its day!

-GT
 
drillher said:
The position of the unit on the base of the tonearm that has the antiskating dial has to be at the correct angle.To move it you need to loosen the two allen screws that you would loosen to adjust the VTA.
Click to expand...

This would be the first thing to try, before trying any adjustments to the magnet underneath the table.
 
garpt said:
Appreciate it all!
so, it's definitely user- servicable for a fairly competent person. It sounds like a really unique and clever system for its day!

-GT
Click to expand...

Mmm... Not so unique. The Lenco L85 predates this turntable and used a similar system AFAIK.
 
drillher said:
How did it work?
Dave
Click to expand...

A coil senses the position of a magnet which is linked to the tonearm position.

There is a high frequency oscillator using the coil. When the magnet is near the coil, strange things happen to the frequency on the coil and this triggers the auto-stop relay.

(This is my cheap explanation, the good explanation is on the manual)
 
I just repaired my TD-145 that wouldn't auto stop. After reading all the comments about mechanical adjustments I have this to say:
If no one has monkeyed with the mechanical adjustment of the coil and magnet, DO NOT TOUCH IT! The circuit is very sensitive to the HFE of the transistors. After measuring voltages and analyzing the circuit I figured out how to troubleshoot it and repair it.
1. The TD-145 manual is garbage. It talks about measuring the AC voltage at point B but it doesn't tell you what postiion the arm is supposed to be in! If you try to set it for 2V when the arm is in the rest, it won't even get close! The TD126 uses almost the identical circuit. You can even use the schematic to troubleshoot the TD145, it's identical except for the control lines on the right hand side of the schematic, but the oscillator, amp, and detector are the same. There is a cardboard gig to position the arm for adjustment. No pictures of it I could find. But the TD126 manual tells you how to adjust the position of the magnet vs the coil with the cardboard gig in place. If no one has messed with it, all you have to do is move the arm so the leading edge of the pole piece of the magnet is 1/3 across the sensor coil. With the arm there, adjust for 2V at point B. If you don't have a meter that is flat out to 80KHz, use a scope and adjust for 2.6V peak.
2. If all that is ok and it still won't work, look at point C with a scope. Point C should be very sensitive. On mine, after I fixed it, Point C was 5V with the arm at the adjustment position, and if you moved it inwards a bit, Point C went to 0V, I think. If it reads higher, you need to remove T104 and check the HFE. It should be greater at least 100. Mine read 20. Replaced it with a 2N3904 that read 130. All fixed.
3. Note that this circuit responds to relative quick movements of the arm, like the end groove or if it's bumped.
 
drillher said:
The position of the unit on the base of the tonearm that has the antiskating dial has to be at the correct angle.To move it you need to loosen the two allen screws that you would loosen to adjust the VTA.
Click to expand...

Do this first; if that doesn't work, do it again.
 
FWIW it is real easy to set up with a scope, BUT the thorens is a live chassis and a scope ground will spark. We always used an isolation transformer (old TV Tech standard equipment)

Also, it's not a magnet but an iron slug - Basically a variable inductor and a tuned circuit.
 
Where the heck were all you guys when I was freaking out about my TD-145 a few weeks ago? I found that messing with the slug mounted to the tonearm was a mistake - on mine as soon as I touched it, it fell apart. I had a horrible time repairing that. But the switch it actuates is adjustable for location in relation to it. I don't have a scope so I had to do it by trial and error.
 
drillher said:
The position of the unit on the base of the tonearm that has the antiskating dial has to be at the correct angle.To move it you need to loosen the two allen screws that you would loosen to adjust the VTA.
Click to expand...
This is a very old thread and not sure if you are even still on the site, but, this was the most outstanding information ever! This fixed my issue which arose after a shop installed a new cartridge for me. The very very precise tweaking of the part you described fixed me right up. Thank you for this info.
 
I'll add this to this old thread: I owned a TD-145 that arrived in great shape with working auto-stop. I made a small adjustment to VTA and never got the auto-stop working properly again. If one isn't a technician the wise course of action is to leave the VTA alone and never try to service the arm or work on the auto mechanism. It's INCREDIBLY finicky.



dr*audio said:
I just repaired my TD-145 that wouldn't auto stop. After reading all the comments about mechanical adjustments I have this to say:
If no one has monkeyed with the mechanical adjustment of the coil and magnet, DO NOT TOUCH IT! The circuit is very sensitive to the HFE of the transistors. After measuring voltages and analyzing the circuit I figured out how to troubleshoot it and repair it.
1. The TD-145 manual is garbage. It talks about measuring the AC voltage at point B but it doesn't tell you what postiion the arm is supposed to be in! If you try to set it for 2V when the arm is in the rest, it won't even get close! The TD126 uses almost the identical circuit. You can even use the schematic to troubleshoot the TD145, it's identical except for the control lines on the right hand side of the schematic, but the oscillator, amp, and detector are the same. There is a cardboard gig to position the arm for adjustment. No pictures of it I could find. But the TD126 manual tells you how to adjust the position of the magnet vs the coil with the cardboard gig in place. If no one has messed with it, all you have to do is move the arm so the leading edge of the pole piece of the magnet is 1/3 across the sensor coil. With the arm there, adjust for 2V at point B. If you don't have a meter that is flat out to 80KHz, use a scope and adjust for 2.6V peak.
2. If all that is ok and it still won't work, look at point C with a scope. Point C should be very sensitive. On mine, after I fixed it, Point C was 5V with the arm at the adjustment position, and if you moved it inwards a bit, Point C went to 0V, I think. If it reads higher, you need to remove T104 and check the HFE. It should be greater at least 100. Mine read 20. Replaced it with a 2N3904 that read 130. All fixed.
3. Note that this circuit responds to relative quick movements of the arm, like the end groove or if it's bumped.
Click to expand...
 
DavidTT said:
I'll add this to this old thread: I owned a TD-145 that arrived in great shape with working auto-stop. I made a small adjustment to VTA and never got the auto-stop working properly again. If one isn't a technician the wise course of action is to leave the VTA alone and never try to service the arm or work on the auto mechanism. It's INCREDIBLY finicky.
Click to expand...
And this is exactly what happened with me. I owned my table since new and while I went through many cartridges never was the VTA messed with. The auto stop always worked. I took mine to a shop to mount a new Ortofon and they adjusted the VTA (incorrectly as it turns out but that is another story) and even after I corrected their misalignment and got it to track properly the auto-stop ceased to work. I could tell that while the tonearm base was going up and down to correct the VTA it was also rotating somewhat and I am sure that was messing with the auto-stop. You are correct about how finicky this was to get back, and I hope it stays fixed now that it appears to be working properly again. Minute movement of the pieces, totally imperceptible to me, and a lot of trial-and-error. I am leaving well enough alone now :-)
 
Anyone have an issue with the autostop where it engages as soon as you turn the Lift knob to drop the needle? I can’t get my tone arm to stay down because the autostop engages as soon as the drop needle knob is turned halfway. I’m thinking my autostop circuit board must be bad, because on the rare occasion I can get the needle to stay down, the auto stop never engages no matter where I move the tonearm across the top of the record.
 
I have a TD-145 and the auto stop feature works intermittently. Most of the time it doesn't work but on a few records I have it does work. Not sure if it's the length of the record or something else but it's only with those records it works which surprises me sometimes. Not sure what I should do about it. it would be great to get it working all the time but correctly adjusting it sounds pretty complicated.
 
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