Radio Conversion

[Joao46]

Anyone in the forum ever adapt a 6 volt positive ground vacuum tube radio to a 12v negative ground car by means of an inverter?

[Bloo]

I've never heard of it. A vacuum tube radio draws a lot of current, so the inverter would have to be quite large, and probably expensive. Also inverters make a bunch of radio noise.

 

Back in the dark ages when this sort of thing was common, it was done by 1) changing the tubes to 12V versions, usually these exist but when they don't, socket rewiring might have been necessary on one or two tubes, and 2) changing the vibrator to a 12V one, and 3) usually changing the vibrator transformer to a 12V one, but in some cases this was not necessary, and 4) making sure there are no polarity sensitive components are still connected directly to the 6V feed. There are usually not, but it needs to be checked. The basic technology of a vibrator power supply and DC powered tube heaters works on either polarity.

 

[Frank DuVal]

42 minutes ago, Bloo said:

3) usually changing the vibrator transformer to a 12V one

Right, otherwise the B+ will be TWICE as high, which will damage components inside the radio.

 

 

[Bloo]

28 minutes ago, Frank DuVal said:

Right, otherwise the B+ will be TWICE as high,

Yes, That should happen. I have heard of cases where it didn't, but I don't completely understand why. In most cases, the transformer will be needed.

 

Edited February 27 by Bloo (see edit history)

[series14]

   I used a 12 to 6volt regulator I found on eBay.  I measured the radio current, and it was between 5 and 6 amp.  I think they called it a buck transformer which was less than $20.  Worked great. 

[Jolly_John]

I have an solid state inverter available....but unfortunately, it's designed to do just the opposite of what you need. The invertor I have for sale is designed to run a 12v item in a 6v system car. I've found the inverter I have is useful for running a CB radio or a modern am/fm/CD player in a 6v collector car. Sorry I couldn't help. John

[Lee H]

Measure the amp draw, and with a little ohms law, you could find the correct resistor value to make it work. R=V/I

Edited February 29 by Lee H (see edit history)

[Frank DuVal]

Yes, but amp draw will vary some depending on speaker volume.😉

 

That being said, back when I worked in an electronics store/shop in the early 70s they still had in stock some wire wound resistors mounted in a box that were just for that purpose! 🛠️  For use in the convert your 6 volt car to 12 volts and keep the same radio/heater.

[Lee H]

In this case, you are doubling the total series resistance, and therefore halving the voltage to the radio, so the resistor needs only to match the radio resistance, and wattage.

 

Or you could just run two of the radios in series 🤓.

[hook]

1 hour ago, Lee H said:

In this case, you are doubling the total series resistance, and therefore halving the voltage to the radio, so the resistor needs only to match the radio resistance, and wattage.

 

Or you could just run two of the radios in series 🤓.

Then you could listen to music and news at the same time.