depotting transformers

Nat Eddy · 11th October 2005, 12:07 PM

Has anyone depotted an epoxy potted transformer? I have a CAL Alpha with the transformer pulled right out, and the leads broken off. Replacements are unobtanium.

SY · 11th October 2005, 12:11 PM

Epoxy is hopeless to remove easily. What you need to do is CAREFULLY chisel it away from near where the wires come out. Once you can expose a few millimeters, new leads can be soldered on.

I just had to do this with some nice UTC transformers- it was a pain, but I've got good connections now. And once the transformers are mounted, no-one can tell without flipping the amp over and removing the bottom plate.

dnsey · 11th October 2005, 03:27 PM

I agree - but I'd 're-pot' the new terminations afterwards. The leads have a nasty habit of breaking again where the digging out has weakened them, and it's almost impossible to repeat the process sucessfully.

SY · 11th October 2005, 04:08 PM

I'm sure there's a way to do that, but everything I've tried on my transformer didn't stick well. Two part epoxy, PMMA resin, two part polyurethane, and hard silicone all let go. I suspect the original potting was a filled phenolic, but I don't know for sure. If you have any suggestions, I'd like to try them.

TwoSpoons · 12th October 2005, 12:20 AM

If you heat epoxy enough (90-120 C IIRC) it becomes jelly like, and is easy to chisel away with a screw driver. It goes back to its glass state as it cools. I've done this with some large epoxy potted high voltage transformers that I used to work with.

I found a hot air gun (paint stripper type) is ideal for heating.

11th October 2005, 12:07 PM	#1
Nat Eddy diyAudio Member Join Date: Feb 2003 Location: Connecticut	depotting transformers Has anyone depotted an epoxy potted transformer? I have a CAL Alpha with the transformer pulled right out, and the leads broken off. Replacements are unobtanium.

11th October 2005, 12:11 PM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Epoxy is hopeless to remove easily. What you need to do is CAREFULLY chisel it away from near where the wires come out. Once you can expose a few millimeters, new leads can be soldered on. I just had to do this with some nice UTC transformers- it was a pain, but I've got good connections now. And once the transformers are mounted, no-one can tell without flipping the amp over and removing the bottom plate. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

11th October 2005, 04:08 PM	#4
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	I'm sure there's a way to do that, but everything I've tried on my transformer didn't stick well. Two part epoxy, PMMA resin, two part polyurethane, and hard silicone all let go. I suspect the original potting was a filled phenolic, but I don't know for sure. If you have any suggestions, I'd like to try them. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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11th October 2005, 03:27 PM	#3
dnsey diyAudio Member Join Date: Mar 2004 Location: Shropshire, England	I agree - but I'd 're-pot' the new terminations afterwards. The leads have a nasty habit of breaking again where the digging out has weakened them, and it's almost impossible to repeat the process sucessfully.

12th October 2005, 12:20 AM	#5
TwoSpoons diyAudio Member Join Date: Oct 2004	If you heat epoxy enough (90-120 C IIRC) it becomes jelly like, and is easy to chisel away with a screw driver. It goes back to its glass state as it cools. I've done this with some large epoxy potted high voltage transformers that I used to work with. I found a hot air gun (paint stripper type) is ideal for heating.

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