[Tgace459]

So...I have a Philco 40-195 that I restored...it's been playing fine till today. When turned on it popped and hissed for a while then went quiet except for a quiet hiss from the speaker.

I broke it down and took to the bench. Via some poking around with a nonconductive probe I touched a resistor or two then HEY PRESTO it started playing....except a power down and power up went back to "dead".

Eventually I narrowed it down to the speaker transformer. I unbolted it and moved it a bit and there was a little sparking and noise then it played again. Until once a again I did an off/on...nothing.

Ultimately I found that if I unbolt it and insulate it from the chassis with some cardboard it plays fine. Any contact between the transformer housing and the chassis causes some (slight) sparking then the radio goes dead. Slide the cardboard back in and it plays.

Is there some sort of short inside the transformer grounding it out? Or is there some other possible cause?

[Radioroslyn]

Simple enough to check be using a dc voltmeter connected from transformer frame + to radio chassis - with the transformer isolated from the chassis. If it is shorted replace it as it can destroy the rectifier tube and power transformer if left shorted to the chassis. Other things to have a look at are the 41 socket (shorts from pins 2 or 3 to ground) bad rubber wiring connecting to those pins. Bad cap from pin 2 to ground or tone sw.

[morzh]

What you describing could point to the oscillator. By touching some of its circuitry you could start it but it won't start on its own. See if the radio oscillates.

[Tgace459]

Simple enough to check be using a dc voltmeter connected from transformer frame + to radio chassis - with the transformer isolated from the chassis. If it is shorted replace it as it can destroy the rectifier tube and power transformer if left shorted to the chassis. Other things to have a look at are the 41 socket (shorts from pins 2 or 3 to ground) bad rubber connecting to those pins. Bad cap from pin 2 to ground or tone sw.

Any chance I can find where the contact is being made and insulate it? Or is it better to just replace entirely?

[Tgace459]

Simple enough to check be using a dc voltmeter connected from transformer frame + to radio chassis - with the transformer isolated from the chassis. If it is shorted replace it as it can destroy the rectifier tube and power transformer if left shorted to the chassis. Other things to have a look at are the 41 socket (shorts from pins 2 or 3 to ground) bad rubber connecting to those pins. Bad cap from pin 2 to ground or tone sw.

Based on the sparking Im getting I believe the transformer case has some current going through it....or the chassis...

[Tgace459]

What you describing could point to the oscillator. By touching some of its circuitry you could start it but it won't start on its own. See if the radio oscillates.

It starts up every time if I have some cardboard between the chassis and output transformer....

[morzh]

I missed that part.
Well.....just use an ohmmeter and see if the primary has continuity to the case.

[Tgace459]

I missed that part.
Well.....just use an ohmmeter and see if the primary has continuity to the case.

Thanks. I will do that!

[Radioroslyn]

I missed that part.
Well.....just use an ohmmeter and see if the primary has continuity to the case.

May work but may not tell the whole story. The primary may need to have the HV present to show the short like if it was arcing.

I think trying to repair the old transformer is a waste of time. I have heard of soaking transformers in polyurethane to try to re insulate them but it depends where to short is. And there is always the possibility of the pri going open at some point too. I think it's just better to replace.

[morzh]

It could be a simple case of something touching something it shouldn't.
It is unlikely inside, I think could be the wire coming out touching. I which case it is simply insulated or re-soldered.