Tube L-49-B

10/28/2010 9:31:08 PMBob

Have an old Firestone Model R-3121 table top with a L-49-B tube in it I can't find tube tester or substitution data on. I assume it's a power tube but that's all I can figure out. Any help would be greatly appreciated.

10/28/2010 10:40:28 PMEdd

Sir Bob. . . . .

As per your surmising of that L49B "tube" to be in the power supply, indeed it sort of is.

It is a thermally trimmed, power ballast resistor guised in a tubes "clothing".

Its basically related to dropping voltage to the proper value for a sets series heater string.

Referencing:

> > > L49B ballast < < <

Couldn't find any info on that Fireless-stone 3121 in my data . . . . . which must mean that it must be Post Neanderthal . . . .pre Cro Magnon vintage . . .

(Meaning that you can't get it to light up, by neither rubbing two sticks together NOR striking flint shards together.)

73's de Edd

I have an ooold Firestone Model R-3121 table top with a L-49-B tube in it I can't find tube tester or substitution data on. I assume it's a power tube but that's all I can figure out. Any help would be greatly appreciated.
:

10/29/2010 12:57:09 AMPeter G. Balazsy

Bob:
Is this the same radio you have?
http://www.radioatticarchives.com/radio.htm?radio=4971

10/29/2010 10:18:14 AMBob

:Bob:
:Is this the same radio you have?
:http://www.radioatticarchives.com/radio.htm?radio=4971
:

:
: Yes, this is the radio in question. Thanks

10/29/2010 1:01:41 AMWarren

An Emerson BJ200 has the L49BG. The "G" is just for glass. This schematic does show the heater string and the dial lamp. Most likely the same set up as yours.

http://www.nostalgiaair.org/Resources/871/M0004871.htm

10/29/2010 1:10:23 AMPeter G. Balazsy

Bob:
This radio uses the same AC voltage for the filaments as your other Emerson does that you asked about using a Zener for to replace the line cord resistor. (elsewhere in this forum)
You can essentially do the same "dropper-cap" fix for this radio to replace the L:49 ballast and save a lot of extra heat.

10/29/2010 1:47:08 AMWarren

Yes you sure can as Peter has said. Here is a link showing how to put that AC capacitor inside the old ballast tube. Scroll down the page to see.

http://www.oldradiosrus.com/build.html

This is my buddy at the San Diego Antique Radio Store here in San Diego.

10/29/2010 10:27:46 AMBob

:Yes you sure can as Peter has said. Here is a link showing how to put that AC capacitor inside the old ballast tube. Scroll down the page to see.
:
:http://www.oldradiosrus.com/build.html
:
:This is my buddy at the San Diego Antique Radio Store here in San Diego.
:
:
:
: Thank you very much. I will follow the advice from this site and Mod the replacement component. You guys are great. Thanks again