I don't understand the idea behind ballast tubes. I own three radios with ballast tubes. All three run very hot and have a unique smell that my non ballast tube radios don't have.
What was the purpose of the ballast tube? The one in the photo below does not appear to be a tube.[img][/img]

In the most basic form, it's just a series resistor to give the right voltage to series-string tube filaments. The filament material has a higher resistance when cold---thus limiting the startup current surge.

They are called "tubes" because they are often put in tube-like enclosures. Are any ballasts under vacuum??---not sure.

Do they always emit a smell? Not offensive, but definitely a different odor than what is emitted by non ballast tube radios.

The dust that has collected inside will smell when heated. Plus any other foreign matter that is in there. Effectively, they are 'fancy' resistors.

Gene

How about if I need to replace a ballast tube? Are they the same or is each radio receiver serviced by a ballast tube with a specific resistance level?


Thank you, fellow ARF members.

I am working on an older set that used 3 6v and 2 25v tubes(300 ma) and a ballast tube that was burned out. I have replaced the ballast tube with 6.5 mfd mylar cap and a 50 ohm resistor for the dial light. This reduces the heat and should be more reliable.

Interesting!

Hi

Sometimes we post this. It explains ways to get around the hot ballast tube/resistor.

http://www.vintage-radio.com/repair-res ... calcs.html

A very interesting web site that I have placed in "my favorites."