Thorens TD125 Power Transfomer

gcalvas · 26th December 2007, 10:29 PM

Does anyone know where I can get the 730-852 transformer? What is the output of the supply? Since I am not getting anything out. I see it going into a full-wave rectifier, but still no output at the 1000uF caps. I hope this is something that can easily be purchased, I hope!

gcalvas · 27th December 2007, 09:55 PM

Does anyone know the specs of this transformer? The OP Amps that it supplies have max values of +/-18VDC. On the other side of the bridge rectifier I should be able to use a +/- 15V DC supply. Does anyone know how much current is required to drive the motor? If I cannot find one, maybe I can build an AC/DC supply either to drive a switcher or a linear. What do you all think?

analog_sa · 27th December 2007, 09:59 PM

Make absolutely sure the transformer is indeed toast. Open primary?

tubenut · 28th December 2007, 08:27 PM

There are different versions of the on board electronics of this deck, not sure about the transformer. When next I look at the one I have hear for a client I will see if I can measure something.

As it is mounted on the TT Chassis and if it is toast, I would have it rewound rather then replaced with something unlikely to fit as well...

Mark Kelly · 29th December 2007, 03:37 AM

According to the manual on Vinyl Engine, on the Mk1 the DC voltage after the full wave rectifier is +/- 16.5V so the transformer is about 25V CT. Since your Mk 2 seems to have the same part number for the transformer (730 852) it should be the same voltage

Since the motor only draws a couple of watts and the class B amplifiers are about 50% efficient, you only need a few VA - anything above 6 should be OK.

Getting the original rewound sounds like a waste of time and effort to me, since moving the transformer outside the TT chassis invariably yields a benefit because all transformers vibrate.

A good plan would be to get a small Hammond box and place the new transformer, a new bridge and two new caps in there and wire the DC output into the old board. There are even three convenient pads which appear to have been designed for this, the three pads in a row about half way along the edge of the board nearest the motor. The one nearest the edge is common, the next one is negative and the third one is positive.

Next step up would be to put a 30V CT transformer, a new bridge, two new caps and a pair of adjustable regulators in the Hammond box and feed the new regulated voltages to the board.

Next step up would be to tear out the entire motor drive and start again, but I digress.

gcalvas · 29th December 2007, 02:23 PM

Quote:

Originally posted by analog_sa
Make absolutely sure the transformer is indeed toast. Open primary?

I checked the AC voltage at the beginning of the wiring prior to it going into the transformer. I have 115VAC. On the secondary side, I removed all the wiring from the board and then I just took a 3K resistor and loaded each side one at a time. I measured the AC output using a Fluke meter. The output was 0 on both legs. It "seems" that the input soldering and wiring going into the transformer look good. Should I take apart and resolder?

analog_sa · 29th December 2007, 02:56 PM

Quote:

Originally posted by gcalvas

Should I take apart and resolder?

You got nothing to lose. Looks like the primary is indeed an open circuit.

26th December 2007, 10:29 PM	#1
gcalvas diyAudio Member Join Date: Dec 2007	Thorens TD125 Power Transfomer Does anyone know where I can get the 730-852 transformer? What is the output of the supply? Since I am not getting anything out. I see it going into a full-wave rectifier, but still no output at the 1000uF caps. I hope this is something that can easily be purchased, I hope!

28th December 2007, 08:27 PM	#4
tubenut diyAudio Member Join Date: Nov 2002 Location: South Africa, Jhb	There are different versions of the on board electronics of this deck, not sure about the transformer. When next I look at the one I have hear for a client I will see if I can measure something. As it is mounted on the TT Chassis and if it is toast, I would have it rewound rather then replaced with something unlikely to fit as well... __________________ Guillaume Croak Audio Exploration

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27th December 2007, 09:55 PM	#2
gcalvas diyAudio Member Join Date: Dec 2007	Does anyone know the specs of this transformer? The OP Amps that it supplies have max values of +/-18VDC. On the other side of the bridge rectifier I should be able to use a +/- 15V DC supply. Does anyone know how much current is required to drive the motor? If I cannot find one, maybe I can build an AC/DC supply either to drive a switcher or a linear. What do you all think?

27th December 2007, 09:59 PM	#3
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	Make absolutely sure the transformer is indeed toast. Open primary?

29th December 2007, 03:37 AM	#5
Mark Kelly diyAudio Member Join Date: Feb 2006 Location: Geelong	According to the manual on Vinyl Engine, on the Mk1 the DC voltage after the full wave rectifier is +/- 16.5V so the transformer is about 25V CT. Since your Mk 2 seems to have the same part number for the transformer (730 852) it should be the same voltage Since the motor only draws a couple of watts and the class B amplifiers are about 50% efficient, you only need a few VA - anything above 6 should be OK. Getting the original rewound sounds like a waste of time and effort to me, since moving the transformer outside the TT chassis invariably yields a benefit because all transformers vibrate. A good plan would be to get a small Hammond box and place the new transformer, a new bridge and two new caps in there and wire the DC output into the old board. There are even three convenient pads which appear to have been designed for this, the three pads in a row about half way along the edge of the board nearest the motor. The one nearest the edge is common, the next one is negative and the third one is positive. Next step up would be to put a 30V CT transformer, a new bridge, two new caps and a pair of adjustable regulators in the Hammond box and feed the new regulated voltages to the board. Next step up would be to tear out the entire motor drive and start again, but I digress.