Thorens TD 125 Mki - capacitor values

music box
timmysteve
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Thorens TD 125 Mki - capacitor values

Post by timmysteve » 15 Jul 2016 14:45

Hi
In the process of restoring and fixing up an old Thorens TD125 Mki. Just taken off the circuit board and noticed that six electrolytic capacitors are not looking too good, bulging, leaking etc. So will need to change them.

My problem is the values. I can see that the two big ones are 2500uf and 40v. I can also see that the other bigger one is 250uf 70v. The other ones though I cannot see the values on the capacitors and the circuit diagram just gives their capacitance of 100uf, 50uf and 25uf.

Does anyone know what the voltage ratings should be for these?

Thanks

paki976
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Re: Thorens TD 125 Mki - capacitor values

Post by paki976 » 15 Jul 2016 16:26

I found those pics on Internet.....
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I see a 25uF 70V cap ,a 50uF 70V, a 100uF 63V,a 250uF 63V.

Ciao,
Fabrizio

tele88
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Re: Thorens TD 125 Mki - capacitor values

Post by tele88 » 15 Jul 2016 17:20

You can forget the big one from 250 uf its for 16 rpm. 100Uf is for 33rpm , 75 uf is for 45rpm best to select these for min.motor vibration .Voltage 40V or 63 Volt is ok.

timmysteve
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Re: Thorens TD 125 Mki - capacitor values

Post by timmysteve » 15 Jul 2016 17:25

Thanks great. Many thanks!

timmysteve
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Re: Thorens TD 125 Mki - capacitor values

Post by timmysteve » 15 Jul 2016 17:29

Would replacing these fix a problem that I am having when I test the DC part of the output voltage as per the manual. When I test it I cannot seem to get a stable reading on the voltmeter. It just goes up and down. Thanks

tele88
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Re: Thorens TD 125 Mki - capacitor values

Post by tele88 » 22 Jul 2016 15:31

timmysteve wrote:Would replacing these fix a problem that I am having when I test the DC part of the output voltage as per the manual. When I test it I cannot seem to get a stable reading on the voltmeter. It just goes up and down. Thanks

This value is not steady how much mV do you measure ?

timmysteve
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Re: Thorens TD 125 Mki - capacitor values

Post by timmysteve » 28 Jul 2016 18:31

Have replaced the capacitors and adjusted the DC output voltage. The manual says to get it low as possible and no greater than 5mv. At the moment I have left it in the minus figures, is this right?

tele88
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Re: Thorens TD 125 Mki - capacitor values

Post by tele88 » 03 Aug 2016 15:03

yes this is ok .

arts
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Re: Thorens TD 125 Mki - capacitor values

Post by arts » 03 Aug 2016 23:15

I would suggest that you also change the ''mustard'' caps at the same time.
Those are the yellow,low value axial types.The values are 0.075,0.1 & 0.2ufd.

In my own TD-125's,all of these caps were misbehaving,and I was unable to get stable adjustments until they were replaced.

And in almost 30 years of working in electronics,I cannot recall one of these types ever requiring replacement in any other piece of equipment.

Clean all of the trim pots with DeoxIt as well.

Good luck!

Art

timmysteve
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Re: Thorens TD 125 Mki - capacitor values

Post by timmysteve » 23 Aug 2016 18:08

When you say you could not get stable adjustments what do you mean exactly? I have not changed these caps yet but have noticed when setting voltages that I cannot get them exact and they will fluctuate around the voltage I want. Will changing these mustard coloured caps rectify this?

arts
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Re: Thorens TD 125 Mki - capacitor values

Post by arts » 26 Aug 2016 20:32

The voltages will always ''bounce'' a little bit,especially when using a DVM,and be somewhat difficult to dial in due to the single turn pots being twitchy in operation.

My problem was that,even after cleaning the trimmers and switches,the voltages were really unstable,and some were beyond the adjustment range of the pots. As all of the resistors had been checked for value,and the drifted ones replaced,these caps were the next possibility.I tested them afterwards, just for the sake of curiosity.They had tolerance issues,and one was erratic.When connected through a high value resistor across a power supply,my scope revealed quite a lot of noise being generated by this cap.

When you perform the adjustments,do an initial set up,then let the unit run for about half an hour to achieve temperature stability,then do a final touch-up.

Hope this helps,

Art

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Re: Thorens TD 125 Mki - capacitor values

Post by varunbadola1974 » 21 Jul 2019 18:31

Hello,
I am reviving this old thread in desperation. I hope I get the required help. For the past one year I have been working on my Thorens TD 125 MK1, which I changed from an AB to LB. a few months back my original motor died on me. The central barrel of the motor broke and I had to buy a new one. After installation, the new motor has shown the same problem off and on. just as the last one, it vibrates at times. I switched it on today and the vibrations could be felt through out the tone arm. with the vibrations, the speed at 33 slowed down. It was slow at 45 too but the vibrations were lesser. Now...the capacitors have all been changed and new ones put in. The film caps have not been touched. though the general consensus is that these film caps do not bother much, but they are at least 50 years old. I intend changing them. But is there anything else that I should be paying attention too? Would rotten film caps make the motor vibrate? I have just set the voltages for all the speeds just a month back and everything seemed to be behaving well. kindly guide me through this. thanks a lot
Varun Badola

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Re: Thorens TD 125 Mki - capacitor values

Post by varunbadola1974 » 21 Jul 2019 18:33

Oh yes...I do not have access to an oscilloscope. Would it be necessary to find one once the film caps are changed?
Thanks.
Varun Badola

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Re: Thorens TD 125 Mki - capacitor values

Post by Onder014 » 21 Jul 2019 19:47

Possibilities:
1. clean or renew the variable resistors
2. clean the switches for speed on the board. Best way is to take apart the mechanism of the board and clean the parts including the print tracks on the board
3. check and finetune the settings for the variable resistors according to the technical manual by a digital multimeter.

Regards,
Henk

varunbadola1974
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Re: Thorens TD 125 Mki - capacitor values

Post by varunbadola1974 » 22 Jul 2019 11:19

I opened up the table today and readjusted the voltages. The vibrations is still there. A friend suggested that what I feel is motor vibration could micro rumble.

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