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Suggest Who Can Rewind Power Transformer Counterpoint SA100?

Basspig

Basspig

Active Member
I have an SA100 with a shorted HV winding. Have been trying to find a place that will either rewind it or make a new one to spec. Contacted six vendors, one said they might be able to make me a new one for under $500. I gave them the dimensions and the winding voltages and application. They said when they run the simulation, it runs too hot. I've been back and forth with them since September and they stopped answering e-mails and phone calls.
Looks like I need to find someone else who can do the job. I used to use a guy name Gary up in Maine, but he's gone now..
Does anyone know a shop that can rewind this odd duck of a transformer?
 
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Basspig said:
I have an SA100 with a shorted HV winding.
Does anyone know a shop that can rewind this odd duck of a transformer?
Click to expand...

Sorry to hear about this situation. So, it is only the tube HV supply that shorted. Do the other coils still work?

I don’t know how much space you have, but could you pancake two toroidal transformers (one for tube HV and heaters, and another for the Mosfet supply), one on top of the other? I will probably try that and if it wouldn’t fit I’ll go for an external transformer with an umbilical cord. But I tend to go for the cheap solution.

This small transformer from Antek will serve the tube section well, and there probably are separate transformers available for your Mosfet supplies. Antek has a 300VA 40Vac x2. Both transformers will cost you under $90.

https://www.antekinc.com/as-05tc250-50va-250vx2-transformer/
 
Is it a part number 12-4-TR? ? From the internet I see it has 2 primaries 100/120VAC, and 3 secondary, 6.3CTVAC, 259VAC, and a third one I think it is a 6VAC. A schematic would help.
Seems like a simple enough PT. If you have an estimation of the current for each secondary windings, you could ask Heyboer for a custom wound PT with the same physical specification.

It is an hybrid so I wonder where the SS power supply is taken from.

If you look here: https://www.canuckaudiomart.com/det...-and-rebuilt-by-mike-elliott-great-condition/

They swap the PT with a toroidal Plitron, as span suggested.

Looks like a common problem on this device.
 
Sorry I am wrong, the 6.3CTVAC is a 34V 68V. That makes sense for the SS amp section.
So the tube section uses the heater 6VAC for the heater and 259V for the HV supply.
 
The specs can be simplified to a single 120 VAC primary. The dual primaries are probably provided to allow worldwide operation with series or parallel connection.

Regards,

Anwesh
 
The reason I can't use the original transformer and piggyback another 270VAC transformer is because the original's is overheating from the shorted winding. If left to run for a few minutes, it will start to smoke.
There is no room for an additional transformer either.

The closest I got to a solution was from Pacific Transformer. They said they could make me an equivalent new unit for just under $500 if I can provide the original specs. I gave them a photo off the top of the transformer which shows the winding diagram and voltages. PacTran got back to me and said that when they ran the simulation, it ran too hot. I suggested we could make the transformer 10% larger in volume and I redrill the chassis to fit, or derate it some for the crest factor of program material. After all, the original was smaller and lasted over 35 years. That's about when they stopped communicating. It looks like they don't want to be bothered making a new transformer.

The numbers are not that legible. I took several photos and sent them to PacTran.

SA100 tfr2.jpg SA100 tfr.jpg
 
I guess here the unknown are the currents needed for the SS amp 34VAC and 68VAC.
For the preamp section we can estimate based on the tube types.

If you have the 2 SS current needs, I am pretty sure Heyboer can do it within the optimal physical space you have.
I've done it in the past with success.
 
Does the transformer smoke when completely unloaded? Meaning, does it smoke when completely removed from the chassis without anything connected to it except only the 120 volts input?
 
Brice said:
Sorry I am wrong, the 6.3CTVAC is a 34V 68V. That makes sense for the SS amp section.
So the tube section uses the heater 6VAC for the heater and 259V for the HV supply.
Click to expand...

Here is a schematic that shows the SS rails are +-53 Vdc. The HV secondary is shown as 250 vac.

upload_2022-12-15_21-28-59.jpeg
 
I recall Heyboer was one of the six companies I contacted in August. They said no can do.
With the secondaries disconnected, the transformer gets warm to the touch after operating for 30 seconds.
 
Might be easier in the long run to watch for a used one to come up at auction and buy it for parts. Or go with the dual toroid approach discussed above.

I'd prefer to spend a little more money and replace the bad transformer with an authentic one from a donor unit. That will maximize resell value later. Trick is finding a "donor" that is otherwise not working but has a good power transformer. I bet one will show up eventually though.
 
kward said:
Might be easier in the long run to watch for a used one to come up at auction and buy it for parts. Or go with the dual toroid approach discussed above.

I'd prefer to spend a little more money and replace the bad transformer with an authentic one from a donor unit. That will maximize resell value later. Trick is finding a "donor" that is otherwise not working but has a good power transformer. I bet one will show up eventually though.
Click to expand...

This is a pretty uncommon amplifier, so finding one for sale is quite rare. Finding a parts unit may mean a wait of years.
 
I just got a quote for $870 to wind an equivalent transformer, this time from Mercury Magnetics. A tad outside of budget..
 
Ouch. Just for a PT... Can't imagine how much they would charge for a good OT.
I would go the Toroidal route, maybe custom too.
 
Or, maybe it is worth it if you want that piece to be as original as possible and if it has sentimental value. I note you can pick up a used SA-100 right now for the same price as what they are charging for the rewinding of that PT. Search for "Counterpoint SA-100" on flea Bay.
 
I guess it's either wait for a parts unit to show up on ebay, or wait and see if PacTran will come around to doing it.
 
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