Would like to know how to bring up a tube radio on a Variac

[Danddd]

I have this mid 40's tube radio console. I bought it about 24 years ago in Des Moines for very little. I used it for a couple of years and haven't plugged it in for at least 15 years. Since joining AK I've learned to bring up old equipment on a variac. I like this radio and plan to clean it up and then get it refurbished eventually.

I'm not sure how to bring up an old tube radio on variac. So I'd like some instructions. Also is an inexpensive...say $49.99 variac on Amazon suffice?

Thanks in advance.

 

[BrassTeacher]

I can't speak to the inexpensive variac, but I revived an old Hammond organ in the following fashion:

Look under the chassis for any cracked insulation on the wires. Replace any that look suspect. Then -
If the radio has a fuse, make sure it is good, and I would put in the fast-blow version even if it calls for a slow blow.
Plug radio into variac, plug variac in, turn everything on. Start with the variac at zero Volts! If the variac does not have.a voltage meter, connect a DMM across the incoming voltage to the radio in as safe a manner as possible. Walk the variac voltage up to ten volts or so. Let it sit 5 - 10 minutes and walk it up to 20. Each time you up the voltage keep your hand on the can cap on the left side of that chassis (looking at it from the back), and make sure it is not getting warm. If all is good so far, after another 10 minutes, walk it up to 30 Volts. Wait ten minutes again, check the filter cap for heat, if cool, go to 40 Volts. Keep repeating the process until either the fuse blows (You should probably start to notice heater glow about 60 Volts, sooner maybe if they are low-voltage heaters), or the filter cap starts getting warm, or you reach 110 Volts. If you make it to 100V without the fuse blowing or the can cap getting warm, test the radio for function. If all is well, power it down and replace that can cap anyway. If the fuse blows, replace the can cap and start the process over again from 0V. If the can cap gets warm before or after 110V, stop, replace the can cap, and start over from 0V. Sense a common theme here? Replace it now, or after a successful test to 110V, but replace it either way.

Good luck, and personally, I wouldn't buy a variac that didn't have a built-in voltmeter.

 

[init4fun]

Why spend $50 on a variac, when a "Dim Bulb tester" will do the same thing for less money

https://antiqueradio.org/dimbulb.htm

And I do agree with BrassTeacher, if the B+ filter can cap ain't dead yet, i'll likely be shortly after it sees power for the first time in at least 15 years. Pretty much all of the wax paper caps that see voltage (first AF amp plate to output amp grid, for example) are likely to be well past prime as well.......

 

[TriodeLuvr]

A Variac isn't the proper approach for equipment this old. The first thing to do is to replace all the electrolytic and coupling caps.

Jack

 

[AlTinkster92]

Keep in mind that these old radios ran on 110-117 volts back in the day, get a bucking transformer when you get it redone and working.

 

[Shawnnnn]

If your plan is to refurbish it there is no point in trying to run it with a variac. It worked the last time you plugged it in so there's no need to test it.

Like Jack said, the old caps have to go. A variac is not going to make them new again.