Thorens TD-125 Mk II power supply - diyAudio
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Old 26th July 2005, 08:06 PM   #1
rmihai is offline rmihai  Canada
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Default Thorens TD-125 Mk II power supply

Hi all,

I am looking to upgrade the power supply of my Thorens TD-125 MK II.

Can you help me, please, with an idea of excellent outboard power supply for it? (money no object)

Thank you
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Old 27th July 2005, 09:01 PM   #2
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Hallo mihai ,
at holgerbarske.com -links-Diy Audio Projekte-Regler für Platine verdier-Projekte
you can find the website from Norbert Bayer and his Thorens Regulator .

Greetings from Germany

Jürgen
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Old 27th July 2005, 10:22 PM   #3
rmihai is offline rmihai  Canada
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Danke Jurgen,

I got it.
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Old 28th July 2005, 03:22 PM   #4
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Default TD125 Power supply

I visited Norbert Bayer's web site and had a look at the Verdier reg, but could not found a reg suitable for Thorens. The Verdier regulator is for DC motors only.

The TD125 has a low voltage synchronous AC motor, which is fed by a sinus generator (switchable and tunable oscillator plus power output). The oscillator and power output work with unregulated DC. At the moment I do not remember whether 12V or 15V.

There are two means to beef up your TD125. First, you could use a larger unregulated power supply by an outboard power transformer, big and fast rectifiers, and big electrolytic caps.

Second, you could use just a regulated DC source (like your standard laboratory DC voltage power supply) and feed the DC directly to the circuit, behind the original rectifying section. Just connect the DC supply to the existing electrolytic cap. You have to disable the original AC supply coming to the board then, but you need the old small power transformer for the strobe light, still. But then, you could install a modern quartz controlled strobe light, instead.

Be careful not to mix plus and ground, or you might see some fireworks.

BTW, being at the power supply board, just replace the old electrolytic cap with a modern one. The old caps are likely going to fail after long years of usage.

BTW, the second method is used by Phonosophie in their P3 record players, which are based on the Thorens TD2001/3001 models.

best regards,
Hartmut
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Old 29th July 2005, 07:31 PM   #5
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What are you trying to do? The TD-125 is specified at .035%flutter and it is difficult to improve on that. It is still very good compared to expensive modern turntables.
Regards,
Ray
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Old 29th July 2005, 07:41 PM   #6
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Forgot this link to the TD 125 service manual at http://www.theanalogdept.com/td125_svc_man.htm .
Regards,
Ray
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Old 3rd August 2005, 03:29 PM   #7
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You could also build Dhaen's oscilator shown in Raka's thread and feed its output directly to the power amp section of the Thorens own psu, bypassing its wien-bridge oscilator.

This will probably not affect flutter, but will likely improve drift.

J.Guilherme
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Old 3rd August 2005, 06:26 PM   #8
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If you look at the schematic in the manual, the power amp is the Wein bridge oscillator. You would have to disconnect the positive feedback network and you would need to replace the light bulb in the negative feedback loop with a resistor to use it as an amp.
Regards,
Ray
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Old 4th August 2005, 12:51 AM   #9
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I was just giving a general idea. Thanks for adding the details.
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Old 11th August 2005, 07:20 AM   #10
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Quote:
You could also build Dhaen's oscilator shown in Raka's thread and feed its output directly to the power amp section of the Thorens own psu, bypassing its wien-bridge oscilator.
You can't do that, the 125 uses a quadrature oscillator. That means in this case two sine waves, shifted by 90°. The Thorens motor (MKII) needs between 3.5 - 6V, not more. Go lightning up yourself (no offence meant)
Rüdiger
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