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Old 7th June 2009, 07:06 AM   #1
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Default Any Transformer Winders?

I grabbed a couple of vintage OPT's from the Bay with the hopes of using them in a project. The wires were very crusty (duh) so I popped off the endbells and tried to solder in new ones, but snapped a primary lead due to some really difficult varnish.

I cut through all the windings and pulled everything off the core, then used an x-acto razor to separate each lamination one by one.

I left the other OPT intact just to show what it looked like. That's an RCA 6SN7GTB for scale. Basically, I'm wondering if this is a salvageable situation. Anyone know where I could get these things re-wound at not too brutal a cost? I have some stuff (tubes etc.) I might be able to barter if that helps. I'm looking for 6 or 8 K primary (UL taps would be nice), to a single 8 ohm secondary.

I would wind the things myself but I'm not quite so hardcore yet with tube DIY.

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Old 7th June 2009, 07:26 AM   #2
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Hi Soren,

Contact Yves at www.dissident-audio.com , he may be able to wind you a bobbin to fit your iron.

Cheers!
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Old 7th June 2009, 10:00 AM   #3
Arnulf is offline Arnulf  Europe
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Complete brand new custom wound OPT of that size (that looks roughly like ~30VA core to me), air-gapped, sandwiched windings (secondary and primary layers interleaved) shouldn't cost more than $40-50 to make. It will cost more in your time or materials to clean up the old rusty laminations and get new bobbins wound. Alternatively you could purchase off the shelf transformers.
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Old 7th June 2009, 06:04 PM   #4
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Yeah I fired Yves an email. In the meantime, is there anything I should try to do with the laminations? Clean them up somehow, or try to re-oxidize the ones that got a bit scraped?
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Old 7th June 2009, 06:26 PM   #5
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by sorenj07
Yeah I fired Yves an email. In the meantime, is there anything I should try to do with the laminations? Clean them up somehow, or try to re-oxidize the ones that got a bit scraped?

After your next barbecue, throw em on the hot coals.

Sheldon
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Old 7th June 2009, 08:05 PM   #6
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Hah really? I have a gas grill, do you suppose that's the same deal? I can maybe ask a friend or something..
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Old 7th June 2009, 10:11 PM   #7
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by sorenj07
Hah really? I have a gas grill, do you suppose that's the same deal? I can maybe ask a friend or something..
Yeah, maybe. You want enough heat to bake off any varnish or potting material. No need to get them red hot, and you don't want to coat them with soot from flames.

Sheldon
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Old 7th June 2009, 10:47 PM   #8
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Hm. I'm a little worried about residue from the varnish doing strange things with the hot metal. Do you think soaking them in a nice big glass jar full of paint thinner or something for a couple weeks would be a good plan? I have a respirator to deal with the fumes
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Old 8th June 2009, 03:23 PM   #9
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Sorenj: Youv'e done well splitting the core: It looked well varnished. How many laminations did you damage = ?
When you clean 'em up make sure varnish is off the ends i.e the E&I faces butt clean together. Avoid over-bending and mechanical handling stampings as this degrades the properties.
There's a limit to this; a 1kW lump is a long boring and sometimes messy job. I use WD40 as a reassemble lubricant.
On re-assembly make sure you keep the job straight to the former: the last thing you want is to nick the 1st and last layers with the laminations by working in haste. That = ruined.

richy
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Old 8th June 2009, 04:13 PM   #10
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by sorenj07
Hm. I'm a little worried about residue from the varnish doing strange things with the hot metal. Do you think soaking them in a nice big glass jar full of paint thinner or something for a couple weeks would be a good plan? I have a respirator to deal with the fumes
Paint thinner probably won't do it. Lacquer thinner or paint remover is more aggressive.

Sheldon
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