Zenith B600 Transoceanic IF Transformer Repair Question

[Geoff]

I am working on my Zenith B600 TO. I had the dreaded silver mica disease and removed the 1st IF transformer, cleaned the mica disc with an eraser, and re-assembled with no issues. During the disassembly of the second IF transformer I ended up breaking the wires from the top coil where they connected to the lugs.



Prior to disassembly I had 26 ohms across this coil. If I test continuity now by connecting alligator clips to the outside of the wires I get none. It's a little hard to see in the following picture but the lower coil that is still connected to the lugs is copper in color until it gets close to the lugs. Then it is silver. The silver wire seems to be inside of the the copper colored wire.



Do these wires have a copper colored insulation on them? If so, how can you strip it off and get to the silver wire underneath? It's so thin I can't see a good way of doing it.

Thanks,
Geoff

[bob91343]

It's probably enamel (paint) coated. Newer types have a coating that comes off with the heat from a soldering iron but the old ones need paint remover or scraping. There is stuff formulated for that but it's a shame to buy a bottle for one job (I haven't been able to remember the name of it). So scrape.

If you use a knife, it's easy to break the wire. Sandpaper works too. Once you see copper you can solder to it.

[Geoff]

Thanks for the tip. I'll give it a try.

[Reece]

Isn't that Litz wire? Look closely. These RF and IF coils are usually wound from this type of wire which is actually a collection of very fine wires. What you're seeing as silver should be the fine wires all soldered together. Carefully scraping the end and turning it over and scraping the other side should reveal all the tiny wires. Twist them together and tin. If not long enough to reach you can splice on a short length of hookup wire.

[bob91343]

I can't tell from the pictures but if it is Litz wire, yes you need to clean off every strand or at least most of them. Use a strong magnifier to see if it's one wire or a bunch.

[old_coot88]

For stripping fine gauge wire, check out post # 26 in this thread. It should work great on Litz wire too.
http://videokarma.org/showthread.php?t=257295&page=2

Also this thread from the rec.antiques.radio+phono NG regarding stripping Litz wire..
https://groups.google.com/forum/m/?f...no/CHx3hk-ifhg

[bob91343]

I think the stuff was called something like Strip-Var.

[Geoff]

Thanks for the tips everyone. Looks like it is 3 fine wires twisted together. I ended up using fine sandpaper to remove the insulation at the end. I had to create a small extension to make up for the shorter wire. WOW, what a pain in the butt these are to work on! The wires are so darned delicate.

Regards,
Geoff

[Reece]

OH yeah! Wait until you have to unwind one halfway to find the break, splice it, and then rewind dripping wax on it hoping and praying that what you "fixed" is going to work!

[Geoff]

Originally Posted by Reece

OH yeah! Wait until you have to unwind one halfway to find the break, splice it, and then rewind dripping wax on it hoping and praying that what you "fixed" is going to work!

Sounds like fun!