[Eric T]

I put in new 600V electrolytics and no change. I decided that it was time to do some actual troubleshooting. I know this is a power supply problem because the detector grid is clean and the speaker hums even when the audio output tubes have been removed, which just ain't right.

So I check the transformer winding resistances. All of them look OK.

Then I checked transformer HV secondary output voltages at the rectifier tube pins. Plate voltages to center tap look about right, 345 VAC on either side. I checked filament voltages to ground next. My DMM shows them as 352 VAC on each side and goes kinda wacky when set to DC. Additionally, it's at 60hz, but should be 120hz if the full wave rectifier was working right and the filtering was bad. This really had me scratching my head because it's a NOS rectifier tube that I checked out in my other radio. How can a known good rectifier not be rectifying?

So just to be sure, I checked plate voltages again, but referenced directly to ground this time. First one reads 698 VAC, next one 0VAC. Eureka!

I had spliced on new wires inside the transformer and used heat shrink over the joints. Once the transformer heated a bit, the heat shrink migrated a little on one end of the HV secondary winding, shorting it to ground. Instead of having two legs at about 350VAC, I have one at 700VAC and the other at 0VAC.

I managed to open the clamshell enough to get in there and wrap electrical tape around the entire secondary side, covering all the splices. I put it back together and checked resistances to ground, and it all looks good.

Unfortunately, the largest bias resistor is now open ( it's a five watt, 150 ohm resistor!!!). I don't have one on hand, either.

Oh well, this will have to wait until I can get a replacement resistor. I guess I'll just go back to work on the little Crosley.