The pilot lamp is in series with the rectifier plate, so yes, the lamp has to be there for the radio work. I don't know what lamp is called for. You might try jumpering across the lamp until you get the radio troubleshot -- that'll put a full 120-V AC across the rectifier tube, but so what.
But the lamp has nothing to do with why the tubes don't light up. This is an AC/DC set with all tube heaters in series across the 120-V line. If one tube blows, none will light.
When you checked your tubes, how did you do it? You can use an ohmeter across the two heater pins of each tube.
If the lamp blows, it may be because part of the rectifier heater is open, and the whole heater current is going through the lamp. Check the rectifier heater. It is tapped for the lamp.
A 35Z5 has filament between pins #2 and #7 with a tap on pin #3. Check continuity with an ohm meter between pin #2 & #7.
If open replace electrolytic filter caps along with 35Z5 & lamp. Shorted filter caps will blow the 35Z5 filament & lamp.
Norm
:Rick: I'm sorry, I misread the schematic. The lamp is not in series with the rectifier plate.
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:If the lamp blows, it may be because part of the rectifier heater is open, and the whole heater current is going through the lamp. Check the rectifier heater. It is tapped for the lamp.
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What tube tester manufacturers do, then, for testing the 35Z5 is they connect both pins 2 and 3 together (you either throw them down and leave pin 7 in the middle or you do vice versa). Then they send 32 volts through the remaining filament segment.
That said, it is entirely possible for the pilot ballast filament in the 35Z5 tube to be burned out, and yet the tube will light and perform perfectly well in a tube tester. When the tube is actually in use in a radio, however, it is usually wired so that current flows through the entire filament. That said, if the lamp ballast portion of the filament is burned out, it won't cause trouble in a tube tester but it will cause trouble in the radio.
The reason why the lamp ballast filament in your 35Z5 tube is burned out is because the pilot lamp is missing and someone operated the radio for some time with it this way. The pilot lamp ballast filament is designed to handle no more than the current that flows through the rest of the filaments. However, what the manufacturers do is first connect a pilot lamp across this ballast filament (pins 2 and 3). This REDUCES the amount of current that flows through the ballast, as some is also flowing through the pilot lamp. However, then they connect the plate of the rectifier (which supplies the entire radio with DC to the plates and cathodes, etc.) to the ballast filament as well. The AC line is connected to pin 2 of the filament. Current flows through the ballast and the pilot lamp to pin 3. Off of pin 3 some current goes to the plate of the rectifier, and also some goes to the remaining filament in the 35Z5 and the rest of the tubes. Under normal circumstances, once the tubes all warm up, the combined tube filament current flowing through the ballast filament and pilot lamp combination is enough to light the pilot lamp to full brightness, and due to the pilot lamp's presence, is not too much current for the ballast filament. However, if the pilot lamp burns out, the ballast filament in the 35Z5 must now handle both filament current and plate current all by itself. This is what stresses it and eventually burns it out.
With the 35Z5 pilot lamp ballast filament now burned out, when you try to replace the pilot lamp, the pilot lamp is not designed to handle even tube filament current, much less the additional plate current if the tubes were able to heat up (they can't, because the pilot lamp blows when you turn on the radio).
So, that said, replace your 35Z5 tube, and replace the #47 pilot lamp, and be sure to replace the #47 pilot lamp immediately after it burns out, should it burn out again. As long as you keep a working #47 pilot lamp in the radio, the 35Z5 ballast filament will never burn out again. When everything is working properly, the ballast operates slightly below its rated current, so it will outlast all of the other tube filaments.
Thomas
Thomas
:I try. Sometimes it is very difficult for me to pull my knowledge out of my brain and put it down on paper (or a computer screen). This is when my explanations don't make sense.
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:Thomas
A couple more things.. Replace the .01 mf cap on pin #3 of your 50L6. If shorted this cap will destroy your rectifier.
When powering up again wire a 60 watt bulb in series with the radio. This will act somewhat like a fuse. If something is shorted the lamp will be bright which should protect the rectifier tube. Don't leave the radio operate if the lamp is bright.
Norm
:Boy! Did I open a can of knowledge. I will get a brand new 35Z5 and put another #47 bulb in and see what happens. I could not pull the schematic up because I don't have the right program in my PC to read it. Rick...
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::I try. Sometimes it is very difficult for me to pull my knowledge out of my brain and put it down on paper (or a computer screen). This is when my explanations don't make sense.
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::Thomas
Rick......goto www.adobe.com and download the free version of Adobe Reader. That is the program that is used to view .pdf format schematics etc.