Another AA5 radio mod, to run off low voltage AC

[wa2ise]

Yet another radio mod, this one I doubt anyone would replicate. At my mom's house there is this 8/16V @ 5A power bus, using the old 1/4 inch Jones plugs. Why these voltages> It dates back from the time we had a model railroad setup, and the lights in it used 8V. I have a few 4BE6's and 4AV6's, and a 17V centertap transformer I could wire backwards to get the plate voltage. The rectifier became made of sand, and the 50C5 became a submini 5902. And the 12BA6 changed to a 6BA6, and a small heater dropping resistor. The B+ came out a little low, around 90VDC, but the radio still works well.

[boora2]

Had a 32 volt tube radio,as as a kid there were these old trains parked in a siding,we used to drink beer and fool around with girls,found if we used a broom to raise the panto graph,36 volt worked the lighting,all 20 100watt bulbs on voltage dropped to 34 volts radio worked fine,had 2 6ba6 rfs, 6cs6 converter,pinched that out of a tv,sync separator tube,6be6 gone to air,2 6ba6 if,had a final if trans with three windings,2 0a91 diodes I avc and 1 audio,and 2 16bm8 audio.

[dieseljeep]

I built a BC band convertor for my BC348 receiver, that doesn't have a BC band.
It was part of a gutted Zenith clock radio. It used the first IF transformer and all the original osc and mixer circuitry. I only had a small 12avc transformer, for a power supply. The 12BE6 worked well with voltage doubler that furnished about 28-30 vdc.
I tuned the receiver to 455 on the 200-500KC band and it seemed to work very well.

[DavGoodlin]

That's pretty neat. Great stories here!
Due to unsanctioned junk being plugged in, I was banned from using 120 volts when I was 8, so I had a model train transformer that would put out enough DC to operate a 1958 Plymouth radio, a Motorola IIRC.

[old_coot88]

When i was about 11 or 12, the family radio, identical to this one.. http://www.sfhobbies.com/sfhobbies/r...jpg&model=6123
needed a new curtain burner cord.
With no replacement available, i stripped the secondary out of my Marx electric train transformer, and wound a new secondary for the heater string supply (about 75 VAC). Mounted the xfmr on the chassis.
Winding it had been real tedious, since there was no way to take the 'bobbin' out of the core. So had to wind it in 4' lengths at a time, splicing them together.

Not having any laquer for the laminations, i used model airplane dope. The radio worked like a charm, but always smelled of airplane dope when it warmed up.

[wa2ise]

Did a little more work on this radio:

Mostly changed the B+ supply to a voltage doubler. Oh, it sags under load, but I still get around 150VDC.

Also changed the 8V supply to a big transformer rated for 15VCT @51A, and used a couple of 7A circuit breakers, one for each 8V output (the 7.5V reads 8V under low loading). Breakers intended I think for mil work, tested them with dead shorts (pop immediately) and a 2X overcurrent (kicks out in about 1 1/2 minutes). This transformer will have a low Thévenin equivalent resistance (like 0.04 ohms), so the voltage will have very small sag. But I definately need overcurrent protection, or else the wires will get hot like a Weller soldering gun element, if a short ever happens. Just like the house wiring protection.

[dieseljeep]

Instead of the sub-mini tube in the output stage, you could've used a 6CU5 type of tube and provided a two volt drop for the heater.
That just my observation!
I still believe your converting proceedures are brilliant. I still follow your advice on using a 6SB7Y instead of a 6SA7 in my Hallicrafters receivers.
Makes for a hotter receiver.