I am trying to make sure this OT is good. I looked at the schematic and it shows a green wire that my transformer does not have.





This is what I got from measuring all of the wires.

The blue & white wire measure 278 ohms. (Suppose to be 262)

orange & blue measure 144 ohms.

orange and white measure 134 ohms.

Black & grounded non-sleeved wire measure .5 ohms. ( I am thinking this is suppose to be .7 black to green)

I think it seems to be ok but I want to make sure I am testing it correctly.

The only thing that really has me confused is it shows 238 ohms next to the orange wire but I have not measured anything close to that one.



Thanks for the help.
Kris

If there is anyone here that can help I really need to find out if this is working today.
Thanks.
Kris

No, it should be 500, per the schematic. You have to add the two values on the primary side.

Given your readings, it would seem obvious that the primary is badly damaged. Comparing your total primary reading to the schematic, you have a 45% loss.

It is rather curious, though, that the orange-white value is so very close to half of what it should be.

I get it now. Thanks for the help Nick.

I hope the other console I have has a good TO in it so I can help Noisebox get his radio working.

Kris

I believe teh Black wire is actually the bare wire going to ground, what you are taking for Black is actually Green but darkened from age.

Try scraping a little of the insulation off it and see if it isn't green.

Hi Eric,
I scraped some off but it still looks black to me. It is hard to tell though it could easily be a dark green.

What should I do with this? Would it still be usable as is in a different radio or is it shot?

Thanks. Kris

The transformer is grounded to itself (the casing), which in turn is grounded to the chassis.

It shouldn't be used, even if you can find a good fit for it in some other radio. It has become unstable and could continue to open up until you only have a few ohms across the primary.

Thanks Nick, I will put it in the scrap pile.
Kris

I still wonder what happed to that green wire. Yanked out?

I think the black wire is actually the "Green" and the wire grounded to the case is the "Black" like Eric pointed out. I pulled this from my chassis and I don't see any green wires in the chassis that got left behind. I have another one of these radios and plan to pull the OT from it also and see if it is any good.

Thanks again for setting me straight. I would have figured this one tested good if I would not have asked.
Kris

You're still missing a wire. The bare wire soldered to the case in the second pic is your ground and you should have 5 other wires, but you only have 4.

Thanks Nick. I will look at the chassis again and see if I can find it in there.
Kris

There is almost never a problem on the secondary (green-black or green to frame). The main issue is the primary side on these, and they are commonly bad on 1940-42 Philco radios. Measure from the center tap (orange) to each outside wire of the primary ( first blue, then the white). dont worry about exact measures, close is ok usually (+ or - 20%). Also check for any ohms reading from FRAME to the primary wires. Should be none, or VERY high lke over 2 meg ohms. Sometimes these can short to frame, then its toasted.

When replacing, use any transformer from any other radio using the same or similar tubes for output. If your radio here uses the type 41 tubes Philco used for instance, look for an OPT from any other radio or phono combo of the 40's using a pair of 6K6 tubes or 6F6 or 6V6. basically any of those would work. Thats what 40's radio-phono combo units are good for... PARTS !

Mark Oppat
www.oldradioparts.net