I am new to ARadio, and not experienced on this topic, I recently acquired a very nice condition 55 ford radio, it appears to be the Motorola version , everything is intact but one resistor is cracked, I am assuming this is 6V positive ground , the cracked resistor sits under the four pin capacitor(assuming thats what it is). I plan to replace the two tubes 6X4 and 6A05. I trying to add some images , any help on how to proceed and where to get parts is appreciated.

Here are instructions for adding images to a post:

https://antiqueradios.com/forums/viewtopic.php?f=2&t=365653

Please don't hook up the radio until you can verify the power connections. If memory serves me correctly my 55 Ford was negative ground, so I would expect the radio to be 6 volt negative ground.

55 was 6 volt pos ground, 56 was 12 volt neg ground. I have owned both.

DM

What difference does ground polarity make on a tube car radio? If it used a synchronous rectifier type vibrator, I could see a problem, but this one uses a 6X4 tube rectifier.

It makes no difference, radio will operate on neg or positive ground. As mentioned '55 Ford was positive ground, changed to neg with switch to 12v in '56.

When I was a kid I ran a positive ground '54 Ford radio on 6vac, viberator wasn't very happy but it did work.

The tubes are probably OK. Look into other things first, like replacing the electrolytic capacitors. Poke around on this site, lots of information about getting your radio up and running. As noted above, resist the temptation to plug it in until you have done your homework and some work on the radio.

If you can add the model number to your post, it might help to be able to find a schematic and identify parts.
Dan

There were 3 radios for 55 Ford passenger cars; model 5BF, a 6-tube made by Bendix (Less said about this radio, the better!), 5MF, a 6-tube by Motorola (Black plastic push-buttons), and 5MF8, an 8-tube by Motorola (Chrome metal push-buttons.) The Motorola radios are good performers and easy to repair. First thing I would replace in either radio would be the “Buffer” capacitor, in this case a .02mfd at 1kv.

Model 5MF information can be found in Sams AR-5 and Sams set 281-4. 5MF8 is also in AR-5 or Sams set 289-4.

Those white porcelain bodied capacitors are going to be leaky; they are paper inside.