Transformer rescue

[mhuss]

I have an amp on the bench (DR201) that got dropped, the huge PT sheared it bolts and yanked all the wires coming out of the PT breaking at least one.

Is there a safe way to remove the transformer coil wrapping (to see if this can be rescued)? Using anything sharp, I'd be afraid of nicking or cutting the windings inside.

[R.G.]

Hmmmm... plastic spudger?

[Stevem]

I have fixed a few output transformers where the feed wires out of core broke there connection to the winding.
The question always comes down to how deep in the winding core did the feed wire go to make its connection to the actual winding.

I use a Xacto knife to cut into and then un-rap the paper and insulation to find the connection point, but this will only work for you if the feed wire is not more then 2 layers deep.

As you cut into the core use extreme care and use super glue to reinforce any connections that you pass thru on your way to the layer you need to get to.

The winding wire itself has a enamel coating so you will need a very hot iron to burn that off and get it to tin up again if you want any hope of getting the external feed wire hooked back up to it again.

Once again if your able to hook it back up and get a good resistance reading then use super glue to hold it there.

I then use epoxy to hold all the feed wires firm to the core.

At this point with at least 1 feed wire busted off you have nothing left to loose by cutting into it.

Oh, you will likely need magnifying glasses to see as needed.

[mhuss]

Thanks for the suggestions.

[didit]

Hello --

I've had to rescue a few. Good advice so far. Careful slow work. Softer tools when possible. Magnifier is a great recommendation. For an adhesive, suggest finding a hi-temp electrical RTV that cures stiff and hard.

Best ..

[wpaulvogel]

Thanks for the suggestions.

The first suggestion I have is to see if possibly you can pass something very thin between the outer paper insulation wrap and the lamination steel to break the varnish layer between the paper and steel. If that’s possible you then can begin to verify carefully attempt to remove the outer layer of paper insulation. This is tedious work but possible and useful something thin and dull (butter knife blade). Same thing as with the varnish to steel process. Once you expose the splices of the magnet wire and the lead wires you hopefully will have just enough magnet wire to re splice the lead wires. Clear tape can work to secure the wires back to the core and this is difficult because you need to thread them through the small window between the core and the steel. Brown craft paper cut into a long strip is then fed through and wrapped around the core. Finding a way to secure it to itself within the steel and not visible from outside is the most visually pleasing way but it’s difficult. Paint on varnish to lock it together and let it dry for a week. Then dip it in the varnish to saturate the splices and insulate everything. If you skip the paint on step the tape adhesive will release and the wrap won’t hold secure. There’s still a possibility of it unwrapping but chances are better after the first varnish application is fully dried. Just in case you wonder, I’ve done this before and it taught me the process for winding transformers at the finishing step.

[mhuss]

All good information, thanks