Fragile old PT wire insulation

[Toxophilite]

As I about to start hooking up the power supply of my amp I was noticing how fragile the PT wire insulation seemed.
I had to extend a couple and upon closer examination it looked like there was some exposed wire right at the entrance to the Bell housing where the fragile wire insulation had cracked and broken, this set off alarm bells, DANGER DANGER!!
This might've been a result of me moving the rectifier socket around and also they pretty well look like they were about to go
The PT is functional m(though  I didn't try it after moving things around and noticing the wires.


Anywho I took out the PT to hopefully address the problem


The problem seems to be on the two beige wires going to the rectifier AC?  and one of the heater wires that go to the power tubes etc


I'm wondering if this is a diminishing returns situation  or can I try and gently take the bell cover off and splice in some new wiring?

[sluckey]

I'd pull the cover. It's possible that some heatshrink tubing is all you'll need. Teflon spaghetti may be another option. And of course, splicing.

I had to replace every wire coming out of the transformer in that old RCA radio that I converted. Pulled the cover and took my time. I treated the PT as a separate project. Ended up with a 60 year old PT with long bright shiny Teflon leads.   

[Toxophilite]

ye gods! It's full of petrified custard!

[sluckey]

Post a couple pics when you recover from shock!

[Toxophilite]

ooops I meant to
I did manage to slide some shrink wrap 4-5 mm past the broken insulation areas
Then my plan was to use some epoxy at the base of the wires to immobilize the problem area
(this picture is of course pre shrink wrapping anything)

[Toxophilite]

here's the PT with some heat shrink on the wires . As the heatshrink transfers the stress point right to where the enter the coil(whilst insulating the wires of course). I plan to immobilize them for a 1/4 or so with some epoxy so the stress point is covcered in heat shrink, thus stronger

[eleventeen]

I think you're doing fine, I would not do the epoxy: The epoxy can melt stuff inside and if you have to re-do the repair, you might have to rip up stuff inside the bell that makes whatever you're concerned about much worse.


If you're careful, slow, methodical, the great majority of these repairs work out just fine. The "immobilization" really occurs when the bell is replaced.....if you can get the heat-shrink covered wires thru the holes in the end-bell. TAPE the wires together, just temporarily, so that you can thread them as a group through the hole in the bell.....without twisting and turning them and inducing exactly the stress you are concerned with. That's often a task. Once that's done and the bell replaced, I like to tie some tie wraps around the bundle of leads that come out of each hole. I use multiple small tie wraps instead of big thick (wide) ones. Why? To get the fat tie wrap tight, you really have to pull on the bundle of wires and that in itself could induce failure. Instead of working to make the bundles of wires absolutely immovable, I think you're better off just trying to minimize their movements, LET them move a little bit, but away from where they enter the bell.


Most of these type repairs work fine.

[Toxophilite]

Cool
I just 'cooked' the PT for a couple hours, it got slightly warm, there were no sparks smells smoke etc.
All the voltages seem to read right so I'll have careful go at reassembly

[pompeiisneaks]

This is the kind of thing that makes this site so cool to me, well done!

~Phil

[uki]

Respect for resources of this planet is something to respect, no waste there ! Well done !