I did a DUMB THING... Philco 39-7 radio - Videokarma.org TV - Video

holmesuser01 · #1 08-26-2010, 05:28 PM

Found this little radio in a pile of trash. All the tubes are in it.

I looked over the chassis a little bit and noticed the 2 electrolytics in the power supply were shot. Replaced them with new ones under the chassis.

Brought it up on my variac. At around 80 volts, I started hearing noise and hum when I touched the cap on the detector. Then, smoke... from the power transformer. Turned it off fast.

Idiot me didnt notice that the wires on the power transformer were no longer insulated at all. Thanks, Philco, for the rubber insulation.

This weekend, I hope to pull the power transformer, open it up to separate the wires, and see if it is actually fried.

This is not my month for power transformers!

Bruce

batterymaker · #2 08-26-2010, 05:59 PM

I think we all have had an oh, SHIT! moment in our collecting lives...

bandersen · #3 08-26-2010, 07:54 PM

Bummer. I hope it's OK.

I have a 39-30 with the same failed rubber insulation. I'm either going to unsolder the end of each wire and slide heat shrink tubing over it or just replace them all.

Chad Hauris · #4 08-26-2010, 09:02 PM

You should be able to remove the bottom cover of the transformer and put heat shrink tubing over the old, bad insulation....taking off the bottom cover will make sure you get the heat shrink tubing all the way up to the core. Also very carefully warming the wires with a heat gun will help in keeping the insulation from shattering off while you repair the wiring. Just be careful not to get the wires too hot and melt the insulation.

bgadow · #5 08-26-2010, 10:38 PM

I messed something up on one of my Philco sets from that era, maybe it was the 38-3? I forget exactly how I did it, but I connected one of the caps wrong. The transformer did not like it one bit-but luckily, after correcting what I had done, it seems no worse for the wear.

dieseljeep · #6 08-28-2010, 08:52 AM

Hi Bruce. I looked up the Riders and that chassis is simular to my 38-12. I thought that model was one that had a rectifier tube on top of the transformer, but that model has a simple two secondary transformer. Realy low B+ on that model. Dave

Adam · #7 08-28-2010, 11:40 AM

I'm restoring a 39-116 now, replacing the rubber wire is a long-slow process. I'm just replacing most of the rubber wire, but I'm going to have to take the cover off the power transformer and put heat-shrink over those wires too.

I like these Philcos, but sure wish they didn't use the rubber wire. After the 39-116, I have a 41-295, and a 41-629 to do.

holmesuser01 · #8 08-28-2010, 01:29 PM

Thanks for the replies. I didnt see the power transformer until I got it home. It's a much nicer radio than I thought it would be when I grabbed it. For some reason, I was expecting something that would be terribly cheap.

The transformer on this chassis stands up sideways. Someone has replaced the OEM speaker with one off of an Operadio set. It fits, but I doubt it is right. Same for the audio output transformer. But, for now, this is the least of my problems.

I sure hope my transformer is not ruined. It was only turned on for about 3 minutes total, and was running thru a Variac with a 2 amp fuse on it. Nothing blew. Nobody before me could have run this set, as the cord, also rubber, was totally rotton.

Of course, this could be very old damage. It was nice, though, that I was getting a signal through most of the radio when the heat started.

I dont trust the 6Z4 in this set. Does anybody know if this tube suffered from the same problems that the early 6X5 rectifiers had? Killing power transformers? I made a tiny adaptor years ago so I could run a (thinking from memory here) 6X4 in place of the 6Z4. I did this for a while in an old Philco that I was playing with until I located a new 6Z4.