tips? cracking insulation on tranny taps!

[G-hoppa]

I'm using the original OT and PT on my Heathkit-to-guitar amp project. I need to re-wire everything-- the original kit owner made a mess. The circa 1957 insulation on the various taps is brittle and cracking as I move it around-- what should I do? These are potted transformers.

Options I can think of:
solder new leads near the base to replace the originals, use shrink insulation over the joint;

use plastic electrical tape or maybe shrink insulation over the whole length of the wires (seems like a bad idea);

just use tape or shrink over the cracks. (seems like asking for trouble later)

Anybody have suggestions?

[Don Moose]

solder new leads near the base to replace the originals, use shrink insulation over the joint;

just use tape or shrink over the cracks. (seems like asking for trouble later)

I like option 1, but I'd want to try to unpot down to where the leads get connected to the actual windings.

Option 2 (black tape) - NO! DANGER!

Option 3 - There's this clear tubing you could get - slip that over the insulation and hit it with a dab of glue at the tranny. Doesn't shrink, but keeps the color, doesn't risk porking the tranny's internal solder joints like option 1 does. I'll see if I can dig up a source in a day or three.

[G-hoppa]

the clear flexible stff sounds perfect-- I was hoping to keep the color if I could. I'll see if they have it at my local electronic place. If you do find a source, let me know--

thanks

[J Martin]

I don't think the color of the tape matters. I have some black paper tape that is an excellent insulator in some spots. If you use electrical tape for anything make sure it is a good grade like 3M # 33 or #88. 88 has held the coax to my antenna masts for years through heat and cold. I never buy the "barrel grade" tapes. Vinyl tape can get gummy where it gets hot, so it doesn't get used in tube amps around here. That out of the way...

The way I deal with crumbling transformer leads is use shrink wrap. Since I run a shop, I have it in many colors. After shrink wrapping, tie off all leads to a lug strip located close to the transformer. This will prevent any further flexing of the leads while you rewire the amp. You can solder and resolder to the lugs with no danger. If you are carefull You will have those transformers for many years to come.

[G-hoppa]

I like the shrink wrap idea-- not sure I have room for the number of lugs(terminal strips maybe?) necessary to provide for all the bunched leads from the 2 trannies. I could anchor them to the tranny mounting bolts with an insulated terminal strip I guess . . .

Is there an easy way to evenly shrink the tubing? What do people use? This is one of those basic skills I lack. I fear I would burn the old insulation under the new shrink, or at least make some ugly looking wires.

[J Martin]

There should be no bunching of leads, cut them short. The insulation is no good anyway. I use the lug strips from Mouser. They fit a #6 screw. Transformer mounts are usually #8. No need to insulate. Some of the grounded lugs can be used for winding center taps or to ground the common from the output transformer so the feedback loop works.

Usually a heat gun is used for heat shrink. Even if you had one it would be difficult to get close enough. I use my soldering iron up away from the tip and stroke quickly along the wire. This does take a little practice as its easy to damage the shrink if you linger in one spot too long. Practice with a piece of scrap wire until you get the hang of it.

[Enzo]

And shrink tubing DOES come in clear.

I used to buy my shrink from Weico wire and cable. I got tired of spending $4-5 for a hunk of tube when the Weico people sold it for 25 cents a foot, or whatever. They get $25 for a 100 foot roll of 1/4" tube, I just looked. $21 for 1/8".

3/4" tube for sleeving guitar plugs is $75 for 100 feet.

http://www.weicowire.com/index.htm

[G-hoppa]

Thanks for all the ideas. I'll use clear shrink tubing from the tranny to terminal strips used as an anchor mounted nearby. Can I get away with an inch or so of untwisted taps between the tranny and the anchor points? There aren't any components nearby. It was trying to twist the leads that caused the insulation to crack. I suppose with the tubing in place I can twist a bit . . .

[WholeToneMusic]

Heat shrink tubing

The heat shrink tubing works great, I use the black and leave some wire on the end for color identification. Let me know how the clear works out if you go with it.

[G-hoppa]

I have high hopes-- I like the idea of having the original colors visible, but protected. I've got a bunch of it coming next week from Enzo's Weicowire.com suggestion.

[G-hoppa]

success with clear shrink tubing

Been a while, but WholeToneMusic wanted to know how it turned out. Answer: great. Weico shipped more than I'll ever use, and it shrank right around the original cracked insulation. Completely clear. So good at making the leads safely flexible again, in fact, that I didn't use any extra lugs, just ran the tranny leads as the original diagram showed.
The amp is almost done-- I took a long break, but now I'm a couple ordered parts away from a test run.

[WholeToneMusic]

Great to hear!! The local Electronics supply around here has the multi color packs of heat shrink and it includes a couple of clear pieces. That sure was alot easier than changing all the leads out!


Best Regards,
Brian