The first two tubes in this radio went dark, looks like they are wire to the speaker jack. This radio has a wood tabletop cabinet. Anyone know what might be wrong with it? What model is it?
9 TTL TUBES
HEAVY
TRF?

Hi JG

All American Mohawk may be the manufacturer? Schematics can be found here:

http://www.nostalgiaair.org/Resources/018/T0000018.htm

Unlikely two tubes would have gone bad at the same time. Check filament solder connections. Two tubes wired to the speaker could be #45? They were often used in push pull to drive a speaker.

Norm

:The first two tubes in this radio went dark, looks like they are wire to the speaker jack. This radio has a wood tabletop cabinet. Anyone know what might be wrong with it? What model is it?
:9 TTL TUBES
:HEAVY
:TRF?

Norm, thanks for your reply. This radio is an All American Mohawk tabletop witha wood cabinet that is long with a lid top that opens, no speaker, 9 tubes, the unlit tubes are 71, I think the rectifier tube is a 24, I can't tell which model it is. A Philco site has a fix for the Audio transformer primary failure to the 71's. Mabey the same circiut. Do you know which model this radio is? The cabinet looks similar to a Radiola. Thanks Norm.

Hi JG

The rectifier should be an 80 tube. Since your radio uses 24 & 71 tubes it was most likely built in 1929. Just about any circuit using the same tubes will be close. Even a circuit with 45 output tubes should help. The 45 has 2.5 volt filament while 71 is 5 volts.

You mention an audio transformer primary failure driving your 71's. AES, www.tubesandmore.com sells replacement audio interstage transformers (A53C). You could also connect a 22K across the open primary and a cap from the driving tube plate to one output tube grid. The secondary of the transformer will invert the signal if you have a second output tube.

Norm

:Norm, thanks for your reply. This radio is an All American Mohawk tabletop witha wood cabinet that is long with a lid top that opens, no speaker, 9 tubes, the unlit tubes are 71, I think the rectifier tube is a 24, I can't tell which model it is. A Philco site has a fix for the Audio transformer primary failure to the 71's. Mabey the same circiut. Do you know which model this radio is? The cabinet looks similar to a Radiola. Thanks Norm.

One other thing.. Check continuity of your 71's with an ohm meter. Check AC voltage at the socket, two large pins. It should be 5 volts. May be a bad solder connection?

Norm

:Norm, thanks for your reply. This radio is an All American Mohawk tabletop witha wood cabinet that is long with a lid top that opens, no speaker, 9 tubes, the unlit tubes are 71, I think the rectifier tube is a 24, I can't tell which model it is. A Philco site has a fix for the Audio transformer primary failure to the 71's. Mabey the same circiut. Do you know which model this radio is? The cabinet looks similar to a Radiola. Thanks Norm.

Thankyou Norm for the great information, I will go to work on this Mohawk.
Regards,
JG

Hi Norm, one of the two 24 tubes filament is glowing very bright, mabey I should change it.

If the 24 filament has a short in it, either to itself, or to the cathode, this would cause it to glow bright. See to it that this is the trouble, and not somehow having the 2.5 volt filament wired to the 5 volt supply.......before replacing the tube. (put the bright 24 in the dim 24's socket)

Thomas

:Hi Norm, one of the two 24 tubes filament is glowing very bright, mabey I should change it.

Thomas, I switched the 24's and the one that glowed still glowed, so it is bad. Hopefully this is the problem with the radio, not the audio transformer primary.
Thanks Thomas

Hello Norm, The transformer next to the 71's has 8 wires going to it. Two of the wires go to the 71's, one to one tube and one to another, both small pins. The voltage is .002 at these pins. Another wire from under the deck, (80 driver?) a blue one, goes to the transformer and measures 240v. Another wire from the same area, which is in the direction of the 80 driver, goes to the + terminal on a grounded metal can (cap?) and then to the transformer, and is at 170v. Could the high voltgage pair of wires be the primary and the low voltage pair be the secondary of the transformer? Does the low voltage on the two wires going to the 70's small pins (.oo2v) reveal any problems? These four wires may be the ones to modify to bypass the transformer primary winding. As far as the rest of the transformer leads, one goes to ground, one goes to the + of the same metal can above, and the other two wires go to the speaker jacks, they have 240v also.
Thanks Norm