The Stovebolt Site Forums The Shop Area The Electrical Bay The Radio Bench '52 GMC Radio; multiple problems?

Hi Folks, I am working on the radio for my '52 GMC. It has not worked since I have owned it. I have it on the bench with a 6v battery, but I will be running it on 12v in the truck (with a 1.2 ohm ballast resistor, as directed in other posts.)
Problem 1: the back of the on-off switch seems to be power related. There are 4 wires: power, lamp power, lamp, and a wire that goes to the transformer. When the switch is turned on, the lamp gets power from the lamp power lead, but the transformer does not get any power from the power lead (I'm assuming that it should.)
Problem 2: Assuming (yeah, I know...) that the lead to the transformer should have power, I applied (fused) power to this wire, and had no response whatsoever. Seems like it isn't drawing any current even when the dead power switch is bypassed.
Problem 3: all of the links I have found to the service manual/ schematic have been dead. Can someone please send it to me? Thanks!
This is about the last big thing to get this truck finished!
http://www.volkmanns.org/1952_gmc_pickup.htm

Thanks in advance, Tom

tombo,
good to hear from someone working on their AD radio! Here is a link that will be helpfull to you:

http://chevy.oldcarmanualproject.com/radios/index.htm

The Old Car Manual project is a little hard to find your way around but this is how to do it. Go to the site and click on site index. Then read the note about the the "Old Chevy manual " project and click on it.

As to your problem, you will not see much of a power draw from the radio unless your vibrator is working. If that is all that is wrong, you should at least have the tubes lit up. Anyhow, I will be glad to help you troubleshoot your radio.

Fred

Thanks Fred. I'm not sure I can read the model number on the tag. Is it anywhere else? Are GMC numbers different from Chevy #s? I don't think the tubes are lighting either. Looking at the manuals, the 511 looks closest to the one I have, with the dial above the speaker. (Actually looks more like this: http://chevy.oldcarmanualproject.com/radios/51rs53.htm )Maybe I can come up with the right number... Tom

Tombo,
from that index that I mentioned, here is one of the pages for your radio:

http://chevy.oldcarmanualproject.com/radios/51rs38.htm

There are actually two models that were the same, except for the dial for GMC and Chev Trucks. The first model went from 1947 to somewhere around 1950 and then the second model went to 1953. They look very similar, almost identical from the front and can be used interchangeably. The earlier radio has a back that has sides cut on an angle and the later one has a straight back. The circuits are very similar but there are some subtle differences.
If you tell me which style you have I will Email you the correct manual pages.

It was quite common for the power portion of the switch to burn out on these radios first. Sometimes you can get away with hooking the radio up to the half that controls the dial light. Sometimes however the burning out of the first portion makes the switch mechanically unstable.

Fred

Fred, That looks like it. It has a flat back. I'll look through this manual; thanks for the link. I'll start by bypassing the switch and seeing if I can get anything going. I'm sure to be having more questions; thanks for your help. Tom

Fred, I have been studying the schematic. I have no power through the switch, and when I jump the switch, I still don't get any hum or tubes lit. My gut tells me I should buy a new vibrator. Is this the likely culpret? I also see a lot of recommendations saying I need to replace all the caps in this radio. Thant is looking like a bigger project than I was looking for! Are there any key caps, or do I really need to replace them all? The $300 overhaul is looking better and better.
Thanks, Tom

Tom,
I would not put a new electronic vibrator in a set that hasn't been done over. If you can get a working mechanical vibrator it would be worth trying it in the radio. If you are bypassing the switch and the vibrator is not buzzing, you probably have a bad vibrator. It is possible in some cases to take the vibrator apart and clean both sets of points and make it work again.

I am a fan of replacing all the paper capacitors as a first step with these old radios. That is pretty standard procedure.

Fred