U.S. Radio model 19B

[DavGoodlin]

I have the chassis and speakers on my bench to repair. It looks like someone did a quality restoration job but it has no sound and Im having trouble tracing circuits.

Its not built like a Philco or RCA of the early 30's and has two speakers, each with center-tapped field coils. One appears to be in the "B-" circuit and puts a split potential on ground.
And the other field appears to be across the B+ supply rather than in series with it. .

The 6mH coil in the plate circuit of the 56 second detector tube was open, so I thought that was IT and got a replacement from Allied. No change - just noise as the volume control is operated. Even tube voltages are hard to measure because the reference points vary I tested the tubes before anything else, no issues there. This is a very confusing set.

HAs anyone worked on one of these ?http://www.nostalgiaair.org/pagesbym...0/M0022160.pdf

[maxhifi]

I would troubleshoot this by signal injection, start at the speaker voice coil, then Primary of output transformer, primary of the phase inverter transformer, then the grid of the preamp, then the detector, etc etc.

If you work backwards you will figure out where the signal stops getting trough.

Very cool radio what's it look like?

[DavGoodlin]

Originally Posted by maxhifi

I would troubleshoot this by signal injection, start at the speaker voice coil, then Primary of output transformer, primary of the phase inverter transformer, then the grid of the preamp, then the detector, etc etc.

If you work backwards you will figure out where the signal stops getting trough.

Very cool radio what's it look like?

Thanks for the help - I have the old EICO 147 tracer ready.
Not sure what the cabinet looks like and I'd have to see if the owner can send me a picture. I does have an AVC control and there are lighted mini-dials for the three pots.

[maxhifi]

Signal tracer definitely will work too, but I would be more inclined to work backwards with this one using an AF generator and an isolating capacitor to verify the audio stages all work first. Once you know audio is fine then proceed to troubleshoot any RF or IF issues. The signal tracer will be your friend then. A bad IF transformer would certainly have the same symptoms.

[DavGoodlin]

The Audio generator used is an EICO 378 with 600 ohm balanced for external load.
I pulled the driver tube and connected the output to the primary of the phase-splitter ( output driver) transformer and got 500Hz nice and clear - power supply and output are cleared!

Next was the 2nd detector - across grid and cathode - louder this time, cleared this stage.

Just skipping over the IF stage its plate voltage was OK, then I checked the 1st detector (oscillator) and the plate was zero volts to B-. Checked terminals on can to verify the open primary.
I pulled the can off and saw the telltale green specks on the winding just above the solder terminal. This coil looks wind-able if I have the right wire but Im trying a surgical repair first.

Thanks for the help!

[maxhifi]

I think I have a few new old stock 262 kc if transformers, let me check tonight. If one of them will work you can have it for shipping.

[DavGoodlin]

Originally Posted by maxhifi

I think I have a few new old stock 262 kc if transformers, let me check tonight. If one of them will work you can have it for shipping.

This one has 3 separate windings and two windings have taps so I probably have to repair it. I still might have to PM you though.

[DavGoodlin]

That oscillator coil winding was on the outside of the form. There were several spots with the green cancer and it was open in three places. Fortunately, again the "open" spots were all at the beginning and end of the winding and only 2-3 turns were lost in the repair

Was this cancer due to a period of humid storage, mold growth that ate protective coatings, allowing oxidation?

Is there a method to cancer-proof more exposed windings which seem to be at risk? brush and encapsulate with spray lacquer? Or just spray with DeOxit and rely on the remaining lubricant to ward off decay?

[Electronic M]

If it is anything like the Ant and Osc. coils in a Philco 60 you can rewind them (or replace turns with) the phono pickup wire Radio Shack(if you can find one still open) sells. I've done three such Philcos the recent ones I got away with patching opens on one, but the other had far too many opens to fix so I simply rewound it with that wire using the same turns count, and it worked well.

[maxhifi]

Awesome, glad to hear it worked out. I would suggest to keep it warm and dry, I think that sort of deterioration happens worse in humid environments or in unheated ones where condensation forms.

[DavGoodlin]

Originally Posted by maxhifi

Awesome, glad to hear it worked out. I would suggest to keep it warm and dry, I think that sort of deterioration happens worse in humid environments or in unheated ones where condensation forms.

The winters here can be very unstable One day its in the teens and dry as a bone, which is fine by me.....then some mild low pressure system blows in with rain and fog - then everything in the detached garage and barn that was cold has condensation on it, lasting for hours - even days Forget about running on ANY tubed equipment during those times. I retreat to heated spaces

[Captainclock]

The company that made your radio was based out of Marion, Indiana I know because I have a 1932 U.S. Gloritone Cathedral Radio that was made by The U.S. Radio and Television Co. of Marion, Indiana, and my radio too had been meticulously restored electrically but then apparently whoever did the restoration work decided they would try to carry the radio by the top of the cabinet and put their fingers through the speaker and the grille cloth so I had to patch the speaker using watered down elmers glue and coffee filters and then now I am going to try and refinish the cabinet and hunt down some new grille cloth to install in the cabinet, put it back together again and then use it to listen to some radio on.

[DavGoodlin]

Originally Posted by Captainclock

The company that made your radio was based out of Marion, Indiana I know because I have a 1932 U.S. Gloritone Cathedral Radio that was made by The U.S. Radio and Television Co. of Marion, Indiana, and my radio too had been meticulously restored electrically but then apparently whoever did the restoration work decided they would try to carry the radio by the top of the cabinet and put their fingers through the speaker and the grille cloth so I had to patch the speaker using watered down elmers glue and coffee filters and then now I am going to try and refinish the cabinet and hunt down some new grille cloth to install in the cabinet, put it back together again and then use it to listen to some radio on.

Thanks for the info. This radio was a customer's and has since gone back to its owner and cabinet. It sure wasn't like the Philco-RCA types Im used to.
I found the variable AVC or "Q" control very unique and it was interesting to dial around at night with the 125 ft outdoor wire connected.
The speakers were made by Utah corp, so I had assumed the radio was one of many makes built in Chicago.

[Captainclock]

Originally Posted by DavGoodlin

Thanks for the info. This radio was a customer's and has since gone back to its owner and cabinet. It sure wasn't like the Philco-RCA types Im used to.
I found the variable AVC or "Q" control very unique and it was interesting to dial around at night with the 125 ft outdoor wire connected.
The speakers were made by Utah corp, so I had assumed the radio was one of many makes built in Chicago.

Mine had a Utah Speaker in it as well and nope it was made in Marion, Indiana The volume control Knob in these radios is actually made by CTS here in Elkhart, indiana which was another dead give away that it was an Indiana based company that made the radio, they sourced the Speaker from Utah because it was the only company at the time that made speakers for companies who didn't make their own inhouse speakers like RCA or Philco did, and actually it makes perfectly good sense that an Indiana company would use Utah for its speakers because Utah Eventually moved to Huntington, Indiana from Chicago.