Mislabeled Tube Misadventure

[Winky Dink]

This is an RCA tube with no discernible identification, which I had labeled “35Z5” at some time in the past. After unsuccessfully trying to use it in an AA5 I noticed that it had only 5 pins--a good indication that it is not a 35Z5GT which has 6 pins.



For high-resolution image go here and click on photo:
https://goo.gl/photos/fDdyFv4PuBPvP1dp8


So, just out of curiosity, what is it? It tested good as a 35Z5 rectifier on transconductance and emissions testers. Pins 2 and 7 are the heater, 31 ohms. Pin 3 taps the heater at 7 ohms/24ohms. Any guesses as to what it might be? And does anyone remember WHY I labeled it “35Z5?”

Apparently the next tube in the series, a 50A5, was injured. As far as I can tell, the 50A5 heater got 120 volts instead of the specified 85 volts. Now it tests as zero transconductance and zero emissions. The heater of course doesn’t light up, but curiously it still shows continuity (31 ohms) across the heater, just as it did before this misadventure.