[TA Forbes]

Working on a 46-420 chassis that has a problem that caused the pilot light to burn out. Not sure what the problem is, but what kind of bulbs do these sets take? These are not what I usually work on, my sets are mainly 1930-38....

[John R]

Hi,
Layout shows a # 44 T3&1/4 bayonet base lamp. John

[Radioroslyn]

Hi Tom
Since the heater string is 150ma I'd go with a #47. The 44 is a 250ma job. I didn't look at the diagram to see if there are resistors in the circuit to limit the current. Also check the paper caps around the 35Z5 those will take out the lamp and the tap on the heater too.
Terry

[TA Forbes]

Thanks, Terry: It had a 47 in it, so I replaced it with a 47 I had and it immediately fried it. All caps have been replaced, I am wondering if either the 50L6 or the 35Z5 is the culprit?? The 35Z5 glows way more than it should before the pilot light blew.

Again, these AC/DC sets are not my usual fare....

[Radioroslyn]

I think I'd find another 35Z5. It may have some sort of cathode to heater leakage. Most of the AC/DC set I've work it is usually the 35Z5 or the 50L6 are were the problems come from. GL I'm sure your get it working properly. Double check to see if your lamp is not shorting to chassis ground.
Terry

[Arran]

Does it have a resistor in parallel with the pilot lamp and the 35Z5 filament? Maybe the filament is shot on one side of the pilot light tap and destroyed the pilot lamp?
Regards
Arran

[LASJayhawk]

Keep in mind the pilot lamp (and part of the 35Z5 filament) is in series with the plate of the 35Z5. If you are drawing too much B+ you will continue to burn out lamps and or tubes.

Some people recommend replacing the tube and pilot lamp at the same time.....