Another Westinghouse H840CK15

[maxhifi]

Originally Posted by trinescope

I did get the transformer working, at least for about a half hour before I heard the sound of insulation breakdown. I did at least get to see the results of the IF and chroma bandpass alignment I had performed. Much better detail and color quality than before. Back to the drawing board on that transformer, though. I was trying to do the convergence procedure when the transformer went bad on me, so I didn't get the chance to take any pictures.

I need to find something for winding layer insulation that has a bit of grip to it so the windings don't move around so much. Kapton is good for insulating the inside and outside of the windings as well as between primary and secondary, but is too slick to hold the individual layers. Double sided tape is too thick for this purpose as it will result in a coil which will not fit in the core window. I used fiberglass resin in a glass jar under vacuum for impregnating, it seemed to work but is too thick, also expensive since I had to throw away over 90% of the material afterwards. I could try something like good old Minwax polyurethane and hope it will cure all the way through. At least the unused portion can be saved. This has been an interesting, although a bit costly learning experience. I would like to try doing some audio output transformers later on down the road with what I have learned so far.

I developed a process for doing the vacuum impregnation which I detailed on audiokarma, have a look here:

https://audiokarma.org/forums/index....t-home.859083/

Results have been extremely good, and I wouldn't hesitate to recommend this method.

[trinescope]

Thanks a lot for the information! I was thinking of thinning the varnish with mineral spirits so it would be thin enough to get inside the windings and insulation. I first need to find a suitable tape for winding layer insulation. I used Kapton the first time around, but it's a bit pricey, has to be ordered in, and wires just slide all over it easily. Masking tape is too thick (5 mil), so I need to use something like regular old Scotch tape. The secondary is the tricky part since it carries 3KV or so of DC and up to 1KV of AC on top of that, and that's in very thin 41AWG wire.

I already have the equipment for doing the impregnation, just need to try again. I really didn't pull a vacuum as long as I needed to since the resin I used had a relatively short work time and I didn't want to end up with a big block of resin with a transformer in it.

[maxhifi]

Originally Posted by trinescope

Thanks a lot for the information! I was thinking of thinning the varnish with mineral spirits so it would be thin enough to get inside the windings and insulation. I first need to find a suitable tape for winding layer insulation. I used Kapton the first time around, but it's a bit pricey, has to be ordered in, and wires just slide all over it easily. Masking tape is too thick (5 mil), so I need to use something like regular old Scotch tape. The secondary is the tricky part since it carries 3KV or so of DC and up to 1KV of AC on top of that, and that's in very thin 41AWG wire.

I already have the equipment for doing the impregnation, just need to try again. I really didn't pull a vacuum as long as I needed to since the resin I used had a relatively short work time and I didn't want to end up with a big block of resin with a transformer in it.

Rather than thinning the varnish, try pre-heating it to reduce viscocity, and also making sure the transformer is well heated to expel moisture. Read through the procedure I linked to, the steps and heating were all based on trial and error - I tried a bunch of iterations to get to that. Long working time of varnish is a good thing. After you're done, unused varnish can be put back into the can and used later.

As for wires sliding all over kapton, why not use something like spray on 3M adhesive to make it a little bit tacky before installing it? Just a light dusting should be enough to hold the wires in place.