Post subject: ballast tubes (see photo) Purpose? Why? How do they work?
Posted: Apr Wed 11, 2012 11:14 am
Joined: Apr Fri 03, 2009 10:32 am Posts: 1369 Location: New Rochelle, NY
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]
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.
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Post subject: Re: ballast tubes (see photo) Purpose? Why? How do they wor
Posted: Apr Wed 11, 2012 1:53 pm
Joined: Jan Thu 01, 1970 1:00 am Posts: 6979 Location: Latham NY
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.