Please help me with Thorens TD125 mk II fault - diyAudio
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Old 27th July 2013, 06:06 PM   #1
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Default Please help me with Thorens TD125 mk II fault

Hi guys

I am really hoping that someone on here can help me identify a problem with a Thorens TD 125 mk II TT I recently bought.

I am so keen to get this fixed as this was my fantasy TT in my teens.

There is absolutely no sign of an power on the TT, essentially it's as if the TT was not plugged into the mains.

I have a basic multimeter and basic knowledge of electronics.


I can get AC on both sides of the fuse under the black plastic cover.

Both poles of the micro switch mounted under the chassis are working.

I have read a similar thread on here but that person had power going to the strobe.


Thank you in advance of an help

Graham

(UK)
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Old 27th July 2013, 06:41 PM   #2
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You may also be getting power to the strobe, but it may be dead.

Check secondary AC voltages on the transformer and DC voltage. If that's ok it's either the motor or the oscillator/driver. Or one of the switches. It will be much easier if you have a scope, or are able to connect your PC sound card to the motor terminals.
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Old 27th July 2013, 07:19 PM   #3
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Default Many thanks for tips, any more please ?

Wow, that's great fast feedback, impressed here indeed

I notice that the secondary winding on the transformer has 3 leads out, and am confused about how to check its output. Any suggestions please ?

Unfortunately I do not have access to a scope, and I fear that would be outside the limits of my knowledge. I have been trying to find a simple step by step guide to take you through servicing but no luck.

I have been trying to get at the slide switches but not sure how to do this or what to clean the contacts with.

Any help at all would be fantastic

Many thanks

Graham
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Old 27th July 2013, 07:57 PM   #4
AuroraB is offline AuroraB  Norway
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You should probably have somewhere around 2x 12-13V on the secondary windings , or 24-26V Ac on the outer legs.....
If you register on Vinylengine, you'll find complete service manuals......
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Last edited by AuroraB; 27th July 2013 at 07:59 PM.
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Old 27th July 2013, 08:03 PM   #5
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Default Thanks again

Thats great Aurora

Have got the pic of the circuit board frm Vinyl engine

The service manual has the circuit diagram but I have no clue how to measure the voltages from the transformer given there are three leads

Hank you so much. I hope I can solve this


Best wishes

Graham
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Old 27th July 2013, 08:32 PM   #6
AuroraB is offline AuroraB  Norway
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Measure between point bl and e and /or f- you should find 12-13 V, and 24-25 V AC betwwen e anf f.

bl is the point in the lower left corner looking at the PCB from the bottom as pictured in the manual page 6. The component placement is on page 5, - as seen from above...
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Old 27th July 2013, 08:49 PM   #7
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Default Great stuff

Thank you Aurora

I'll get on to this tomorrow. At least I should be able to narrow the fault down and ideally get a spare part somewhere

Am I right in thinking that BL is a common ground rail from the transformer ?


Graham
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Old 26th December 2013, 02:17 PM   #8
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Default TD 125 fault continues

Hello all,

I hope Christmas went well for everyone. I am continuing to try and fix my Thorens TD125 mk ii TT, after several months of failed attempts.

I have again attempted to re calibrate the speeds on the TT by following the TD 125 mk ii service manual on Vinyl engine, as follows;

Connect meter (dmm) to test points ge and rt (phase 1) and adjust:
45rpm set R10 for 6V
33rpm set R9 for 5V
16rpm set R8 for 3.2V


connect meter to test points ge and bl (phase 2) and adjust:
45rpm set R13 for 6V
33rpm set R12 for 5V
16rpm set R11 for 3.2V


Speed adjust:

set pitch control to centre position and adjust:
45rpm set R18 for stationary display on strobe ring
33rpm set R20 for stationary display on strobe ring

16rpm set R22 for stationary display on strobe ring

Repeat until no further change noted.

16 rpm and 45 rpm are setting perfectly, but despite repeatedly measuring the voltages and re setting the PCB pots over several months, I am still unable to set the 33 speed so that the strobe is stationary. I am wondering if one of the components, which are specific to the 33 speed (R21 and C12) might be at fault. I am assuming that the TT has been mostly used on 33 over the years and therefore components are likely to at fault when in this speed setting ?

Any help would be really appreciated.

Happy New Year everyone.

Graham
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Old 27th December 2013, 05:56 PM   #9
kevinkr is offline kevinkr  United States
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You should plan on replacing all of the electrolytic capacitors on the PCB, and the caps and resistors associated with the 33 rpm speed setting unless you can diagnose specifically what part is bad.
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Old 1st January 2014, 04:20 PM   #10
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Default Problem solved.....Very stange brain teaser

Happy New Year guys

Ok this one is very strange indeed.* After months of trying to fix my Thorens TD 125 mk II, I have solved the problem, but have no cle how this works.

After finding an App called iRPM for my IPhone, I thought I'd experiment with it on my Thorens.

A complete a complete failure* to set the strobe properly on 33 speed I used the iRPM app to measure tge platter speed on each speed setting.

Whilst adjusting the speed control pot (20) for 33 speed and observing tge patter speed I have managed to lock all 3 speeds. Tge strobe is stationary on 16 and 45 rpm. But I still can't set 33 to be still, even though tge iRPM app gives the speed as 33.3.* Weird ?* *Makes me wonder how accurate these turntable strobes are.*

So to summarise, the 33 speed is now stable according to the iRPM app but not on the TT strobe


Any clues to explain this guys ?* *

Sitting here listening to the Thorens with Shure V15 iii and the improvement over my previously used AT 95e and Shure M75ED ii is staggering.

One happy bunny here

Any clues guys ?

Graham
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