TubeNet

Hey this is a call to all the car buffs out there (if there are any). I got this old buick, a 1937 straight eight LEAD SLED. It's in an unrestored state and runs great, 38,000 miles. I'd love to get the radio working again. It's an AM radio TUBE. It has power but no sound. I suspect a bad tube (it's never been replaced in 71years). Any advice/suggestions? Comments?

This is a long shot but if there any ham radio clubs in your area, they frequently will have a web site with some contact info. From there it is within the realm of reasonable possibility you can find somebody with a tube tester (of which I have two) ... and maybe (if the gods are really smiling) some tubes.

Google "antique automobile radio" and you'll find several pages of restorers.

I'd love to do this on my own (as in not paying for somebody else to do the work for me), I promised my grandmother I'd restore this old car and she up and gave it to me! Now that I have I realize how much studying I need to do before I dive into it.

Just to muddy up the water a little more ...
My guess is that if the tubes were working when the radio was last on, there is a good chance the tubes are still working. About the only thing that would mess them up is if air managed to get in through where the pins exit the bottom.

However, all those resistors and capacitors that make the tubes happy, have a tendency to change value or go bad. Checking the tubes is probably the easiest first thing to do. After that, the doodoo gets deeper, and slogging gets slower. Some of that stuff will probably have to be unsoldered to check it. And I'll bet finding somebody with a capacitor checker (that works) is harder than finding a tube checker.

Most often (experience from dealing with my Great-Grandmother's 1949 Chevy which we still have in storage) what goes out on these old radios is the mechanism that induces the DC to AC in order for it to be transformed to proper plate voltages and other bias voltages to run the tubes. Yes -- they're called vibrators.

To quote Harry Callahan: a man has got to know his limitations. I have torn down my Jaguar E-type engine and rebuilt the head and carburetors myself after it had been sugared. The engine, mechanical and body work are not that bad to do yourself. But the radio takes specialized parts that not all are being currently manufactured, and may have to rely on NOS. It would be better to spend a little cash having someone else fix it for you rather than spend a little to a lot more money unless you're experienced with the electronics. The same way, I'll fix a lot of things on my electric guitars, but I send all my tuba repair work out.

By chance have you checked the speaker?The "cardboard" cone may be the main problem.
Just my .02
Dave Hayami

No sound comes out, so I dont think its the speaker cone. I have had a few old speakers that weren't conected by cardboard all the way around it still made a noise. (not a very good sound )

still made a noise. (not a very good sound )

It must be working then. You just described most of the radio stations.

The tubes may still be okay. If their seals are still good, they probably still have a reasonable vacuum and will work.

The biggest problem will be capacitors, or "condensers" as they called them in those days. The old capacitors used wax paper as a dielectric, and the wax will have dried out rendering the capacitor leaky (for electrical current, that is). Sometimes you can reform the capacitors by bringing the power up very slowly over a long period, but you are probably better off replacing them with rebuilt capacitors. Bring your checkbook.

Tubes are pretty robust, as long as they still have their vacuum. If the filaments light and there are no shorts, then the only potential problem is air contamination, which brings humidity that will provide an arc path and oxygen that will cause corrosion. If the silvery patch on the inside of the tube is still mirror-like, though, it might be okay. That patch is made by the "getter", which is a heated element of special metals there to "get" stray air molecules, but it emits metal molecules that mirror the nearby inside surface of the glass. If the seals are gone, that silvery patch is probably white and chalky by now.

It's best to power the filaments and getters in the tubes for a day or two before applying plate voltage or grid bias. Obviously, this should be done by someone with the expertise and fixtures. That would NOT include ANY modern electronics repair house. Follow advice and go to an old radio amateur or a specialty restorer.

Rick "who just added another tube-type radio transmitter amplifier to the collection" Denney