[Paul D]

Figured I would start a new thread on this....

I re-capped the radio last week and turned it on. It worked for about 30 seconds then it blew the rectifier tube. I determined that it cooked the heater element. Chuck is sending me the actual schematic, but I figure I can at least start some troubleshooting now.

The radio has the same tubeset and tube heater wiring as a 46-250. I noticed that the rectifier is the first heater in the circuit (going from + to B-), then it goes through an 80 Ohm ballast resistor, then on to the other heaters on the other tubes. All the other tubes are ok.

When the set was turned on my assistant (my 16 year old) noticed that the tube initally glowed normal, then would increase in brightness until the he saw a flash in the tube, which of course was the heater element failing. He also noticed that when the rectifier tube became brighter, the other tubes got dimmer, which I can only suspect was the heater in the rectifier losing resistance and starting to fail.

I checked the ballast resistor and it does read 80 ohms cold (matching the schematic) and I cannot find any shorts in the wires in this circuit.

The ballast resistor is Philco part number 33-3425-3 and it is riveted to the chassis.

Could I have a bad ballast resistor that is shorting to B- as current is passed through it or am I barking up the wrong tree?

Since the other tubes are ok I am assuming that the problem lies somewhere between the rectifier tube socket and the wire leading to the second tube in line. But then again, who knows???

Thanks in advance for any advice
Paul

[Arran]

What about the pilot lamp? Was it in place and functioning when this happened? Is the wiring to the pilot lamp socket in good condition? Other then a short in the filament circuit someplace the only other thing that I can think of is something in the B+ circuitry loading down the rectifier.
Regards
Arran

[Paul D]

It was functioning ok- but I will be sure to double check tonight. The filament is good, but I haven't looked super close at that wiring....

Thanks for the reply

Paul