I'm working on Air-King from the late 1930's. It seems to be a Model 21, but the tube types do not match the schematic available on Nostalgia Air. Here is what is in the radio:
6D6 (Six Pins)
6c6 (Six Pins)
25A7G (Octal)
M80F (Octal, Made in USA by Hytron)

I cannot find any info on the M80F tube. The heater is burned out, so this project is going nowhere unless there is a suitable replacement. Suggestions appreciated.
I'll try to post some photos here:

Case
http://aycu02.webshots.com/image/24121/2004178274511448646_rs.jpg

Chassis Back
http://aycu18.webshots.com/image/24097/2004166068951685620_rs.jpg

Chassis Top
http://aycu33.webshots.com/image/21432/2004198039036009526_rs.jpg

Tube
http://aycu37.webshots.com/image/22036/2004121934433716728_rs.jpg

I'll try the photos again:

Case
[URL=http://allyoucanupload.webshots.com/v/2004178274511448646][IMG]http://aycu02.webshots.com/ima

ge/24121/2004178274511448646_th.jpg[/IMG][/URL]

Chassis Back
[URL=http://allyoucanupload.webshots.com/v/2004166068951685620][IMG]http://aycu18.webshots.com/ima

ge/24097/2004166068951685620_th.jpg[/IMG][/URL]

Chassis Top
[URL=http://allyoucanupload.webshots.com/v/2004198039036009526][IMG]http://aycu33.webshots.com/ima

ge/21432/2004198039036009526_th.jpg[/IMG][/URL]

Tube
[URL=http://allyoucanupload.webshots.com/v/2004198039036009526][IMG]http://aycu33.webshots.com/ima

ge/21432/2004198039036009526_rs.jpg[/IMG][/URL]

Rob

I was able to view your photo. Your M80F is a ballast tube. It will be wired in series with tube filaments and acts as a dropping resistor. In operation it will be very hot.

M80F is rated to drop 80 volts @ 300 ma. According to the book it has two resistors built in. One between pins 2 and 3 and the other between 7 and 8. As long as you have resistance readings between these pins the tube is good.

Norm

:I'll try the photos again:
:
:Case
:[URL=http://allyoucanupload.webshots.com/v/2004178274511448646][IMG]http://aycu02.webshots.com/ima
:
:ge/24121/2004178274511448646_th.jpg[/IMG][/URL]
:
:Chassis Back
:[URL=http://allyoucanupload.webshots.com/v/2004166068951685620][IMG]http://aycu18.webshots.com/ima
:
:ge/24097/2004166068951685620_th.jpg[/IMG][/URL]
:
:Chassis Top
:[URL=http://allyoucanupload.webshots.com/v/2004198039036009526][IMG]http://aycu33.webshots.com/ima
:
:ge/21432/2004198039036009526_th.jpg[/IMG][/URL]
:
:Tube
:[URL=http://allyoucanupload.webshots.com/v/2004198039036009526][IMG]http://aycu33.webshots.com/ima
:
:ge/21432/2004198039036009526_rs.jpg[/IMG][/URL]

You can buy universal replacements from www.tubesandmore.com. Look for one with similar resistances. You may need to rewire the socket, but that's no big deal. You might also be able to use a non-polarized cap of appropriate capacitance as a cool replacement for the ballast tube. For the pilot lamp, parallel with the same size resistor as was originally specified. Then also parallel the pilot lamp with two 6.8 to 7.0 volt (whatever you can obtain) zener diodes wired in series, back-to-back. The zeners will protect the pilot lamp from surges that occur when capacitance reduction is used in place of resistance reduction.

Thomas

Thomas

:I'm working on Air-King from the late 1930's. It seems to be a Model 21, but the tube types do not match the schematic available on Nostalgia Air. Here is what is in the radio:
:6D6 (Six Pins)
:6c6 (Six Pins)
:25A7G (Octal)
:M80F (Octal, Made in USA by Hytron)
:
:I cannot find any info on the M80F tube. The heater is burned out, so this project is going nowhere unless there is a suitable replacement. Suggestions appreciated.
:I'll try to post some photos here:
:
:Case
:http://aycu02.webshots.com/image/24121/2004178274511448646_rs.jpg
:
:Chassis Back
:http://aycu18.webshots.com/image/24097/2004166068951685620_rs.jpg
:
:Chassis Top
:http://aycu33.webshots.com/image/21432/2004198039036009526_rs.jpg
:
:Tube
:http://aycu37.webshots.com/image/22036/2004121934433716728_rs.jpg

Rob,
I believe your radio may be a model 214:
http://www.nostalgiaair.org/PagesByModel/302/M0000302.pdf
Carl T

Many thanks to each of you. This is the oldest radio that I have worked on and the first time to come across a ballast tube.

:I'm working on Air-King from the late 1930's. It seems to be a Model 21, but the tube types do not match the schematic available on Nostalgia Air. Here is what is in the radio:
:6D6 (Six Pins)
:6c6 (Six Pins)
:25A7G (Octal)
:M80F (Octal, Made in USA by Hytron)
:
:I cannot find any info on the M80F tube. The heater is burned out, so this project is going nowhere unless there is a suitable replacement. Suggestions appreciated.
:I'll try to post some photos here:
:
:Case
:http://aycu02.webshots.com/image/24121/2004178274511448646_rs.jpg
:
:Chassis Back
:http://aycu18.webshots.com/image/24097/2004166068951685620_rs.jpg
:
:Chassis Top
:http://aycu33.webshots.com/image/21432/2004198039036009526_rs.jpg
:
:Tube
:http://aycu37.webshots.com/image/22036/2004121934433716728_rs.jpg