Tube tech?

**HotHead** · 03-28-2011, 04:13 PM

Re: Tube tech?

I should of put the make and model.

It's a Victor (1939) A-31 Globe Trotter

**japlytic** · 03-28-2011, 07:45 PM

Re: Tube tech?

According to http://www.classaxe.com/wireless/data/sets/ , this set can do the AM band.
Replace all of the paper capacitors with polyester units (you can hide the new ones in the old ones if you want), reform the electrolytic capacitors and check the tolerance of the resistors.
Check the oscillator, RF, IF and speaker transformers for continunity.
When powering on for the first time, use a series lamp limiter. If it glows brightly, you may have a problem.
The heaters in metal tubes are a bit hard to tell if they are working or not; the only way I can think of is to measure the resistance between the heaters, or if they draw heater current.

**kc8adu** · 03-28-2011, 09:12 PM

Re: Tube tech?

dirty bandswitch?
weak oscillator tube dropping out?
this set needs a complete overhaul.all wax and lytic caps first off.then dig out the remaining bugs.

**bluto** · 03-28-2011, 09:16 PM

Re: Tube tech?

^^^^^^^^^^^^^^^ This!!! Be sure to do the light bulb trick when you finally go to power it up. And as one site put it: "For the love of Marconi, don't plug it in yet!" You will probably want to replace the main filter caps (the old ones are big aluminum tubes filled with liquid). You may also want to replace all of the wax capacitors and probably some of the resistors too.

Once you have done this try the light bulb inline with the power cord. If all is well, it will glow dimly or flicker a little. Once that is OK you could move on to using a variac to bring up the voltage slowly while carefully looking for hot components and magic smoke. If all goes well, keep raising the voltage and hopefully the radio will start to "sing".

Some links:
http://antiqueradio.org/begin.htm
http://www.nostalgiaair.org/ (schematics)
http://antiqueradios.com/ (forums and info)

It's not too hard, I restored an old Zenith model 807 a few years ago with no previous antique radio experience. It had been languishing in a moldy basement for years. I replaced the speaker, all the caps and resistors, as well as the power cord. No tubes needed replacing. I also gave it a good cleaning and some minor restoration to the cabinet and now it is almost as good as new! And it plays great too! (although there is not much to worth listening to on AM and SW these days)

But it is pretty neat to hear it play (in today's world of 50 inch plasmas and 500 channels of satellite TV) and think about how it was once cutting edge for technology and entertainment.

Some before and after pics:

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