[jrblasde]

Perfect! I do not have a variac, but I can quickly use the dimmer. I do have an isolation transformer that I’ll definitely be using.

[jrblasde]

I started disassembling the transformer from the chassis, and it's not good. Directly on the underside of the chassis from this power transformer is the audio output transformer. I needed to remove the output transformer to get to the wiring from the power transformer, which passes through a grommet to the underside of the chassis. Once I removed the audio output transformer, I saw that all of the insulation on the wiring had either flaked off of the cables already or began flaking off as I touch the wires.

I don't dare to plug this in. I think I will keep investigating a rewind. I will also speak to Edcor and to Heyboer to see what they could quote me. I also have sent an email to Mark Oppat to see if he's got a comparable transformer. His website said to contact him to ask about transformers. 

A side note, but my first job out of college was an audio-video systems engineer. We used Edcor transformers quite the bit. Nice products!

[Arran]

I think you could start by Ohming out the various windings on the transformer, the H.V secondary is usually the one that fails first, the resistance on either side of the H.V center tap should be fairly close, like 35 to 40 ohms, give or take 5 Ohms per side, the rectifier heater winding should be something like 1.2 Ohms, the 6.3 volt winding 1.5 Ohms. Crumbling insulation may or may not be an issue, other then you would have to replace the transformer leads, or sleave them. If the transformer is bad they usually have a strong odor of burned varnish, and tar, along with the paper being charred. 
  I tried to look at the Edcor site but it does not seem to work with Brave Browser, some don't if they have cookies, or block ad blockers. Antique Electronic Supply also has some replacement transformers for tube type guitar amps, both vertical and horizontal mount, the one in the Philco looks like a vertical mount which makes it easier to fit a replacement, none are cheap but all would be cheaper then getting the factory one rewound if it really is shot. 
Regards
Arran

[TV MAN]

Again, don't assume it is bad. Sleeving can be accomplished with shrink wrap. Some isolation transformers have voltage settings that you can kinda use like a variac, and start out with lower voltages. Some do not. +1 on the HV winding usually being the one that goes bad, due to shorted filter caps, tube, etc. But, don't assume it's bad my looks. It could be perfectly fine. Try to keep your colors or somehow mark the leads so you know what goes to what.

[GarySP]

I don't think Mark winds transformers, but his website says contact him for transformer needs. If it gets to this point what is to be lost by trying? Take care and BE HEALTHY! Gary
P.S. Welcome to gutta-percha insulation. It's not the end of the world. As Tim said, sleeve the wire with shrink tubing. If you choose to replace the wires route the new wire exactly like the original was. I've got a 40-180 myself in the bullpen. It is behind my other two consoles, a Philco 41-280X and a Freed - Eisemann neutradyne battery set. All are on hold for medical limitations. Take care and BE HEALTHY! Gary

[jrblasde]

I get readings of 113 ohms and 106 ohms from each side of the HV to the center tap. For the 6.4V, 3.45A rectifier output, I get 0.6 ohms. for the 6.4V center tapped, 0.3A filament output I get 1.6 ohms (0.8 ohms from each side to the center tap).

[morzh]

Do not use dimmer.
This is not what they meant by dim bulb.

[jrblasde]

I reread that discussion, and I realize that I had misunderstood. I am glad you said something! Okay, so I will simply install a lightbulb in series with the radio’s primary winding while testing.

[Arran]

From those readings the power transformer secondary's sound like they are fine, as long as the primary isn't cremated I think that replacing the leads, or sleaving them should do the job.
Regards
Arran

[jrblasde]

This is really promising news. I’ve been afraid, but it sounds as though I’ve worried for no good reason. I’ll get this transformer cleaned up and do the wires re-insulated, and then continue with some more extensive testing.

As for stripping the rust, should I stick to dry methods such as a wire wheel? Or is it safe to use rust removers on a transformer?

[Arran]

Is it safe to remove rust on the transformer? It's perfectly safe to use whatever method you like on the bells/covers. If you mean the iron laminations in the core, a small wire wheel followed by something like phosphoric acid should take care of it, or Naval Jelly if you have some, just to kill the rust, you can also paint them black, some companies painted the iron, some did not. However I would suggest using a wire wheel outside, or in a garage, they throw around a lot of dust, and bristles.
Regards
Arran

[GarySP]

I would take the transformer out and wire wheel it FAR AWAY from the rest of the chassis. Don't need conductive Iron Oxide (rust) particles floating around in the chassis. Take the bells off and re-sleeve the wires while it's easy to do. My $0.02. Take care and BE HEALTHY!! Gary

[jrblasde]

Thank you all for the advice. I’ll remove it from the chassis and get it cleaned up with a wire wheel. I can take it out to the garage to do that. I will also order new sleeve material, likely tomorrow. I’d like to match the original coloring.

For certain I’ll repaint the bells. I’ve also heard of people applying a clear coat to the exterior of the laminated metal after cleaning them. I might just do that, provided that the material looks presentable after cleaning. Otherwise I’ll just go with solid black. Regardless I plan to paint the bells black.

I should ask, what is naval jelly? I’ve seen it written here before.

[DaleHCook]

Naval jelly is a rust-removing gel containing phosphoric acid. I do not recommend using it on anything that cannot sustain a long and thorough rinse to remove the remaining acid, and that eliminates transformers.

[jrblasde]

Noted, thank you for elaborating. I’ll steer clear of it on this transformer. I may only need a wire wheel, but I could probably scrub on it some with a pretty dry paste of baking soda and a tooth brush if I need to do a bit of fine tuning.

My favorite rust treatment is 6% vinegar, but that requires a long soak as well. Obviously that’s off the table for this application.