GU-39b Heater

The GU-39b is a transmitting tetrode with 8000 watt plate dissipation and a 6.3 volt 100 amp heater. Sadly one of the parallel-running heater filamens appears to be broken so the tube won't reach full emission current. I would be really grateful if someone could sell me or exchange for a similar healthy tube, I am in search of one of these for a long time, and when I finally get it - it's kind of damaged... :-(

Category:

Science & Technology

Tags:

• vaccum
• tube
• transmitting
• tetrode
• thermionic
• valve
• heater
• direct
• heating
• external
• anode
• vttc

[danrulz98]

What a shame :( Beautiful tube.

What is that transformer you're using?

[jmartis2]

@danrulz98 It's an old ?welding? transformer with 7 turns of 50 mm^2 welding cable wound around it (there was just enough space left to fit those turns).

The tube is still operational however, I think I wont use it to its max ratings anyway, but there's always the risk of the filament remnants shorting out something inside the system - that I'm most afraid of.

[MarshmallowVogt]

I sure wish I could understand what you were saying the things you do are so cool I'm sure if I tried I could get a lot of people watch a video of me electrocuting myself lol

[jmartis2]

@ubuntupokemoninc It will not, just make sure you don't get arc overs to it. It could, however, generate some x-rays if it's an all glass tube.

[favret94]

Don't worry, the same thing happened to me, when i finally found and bought a GMI2-b after some years and i tryed it, i found that the heater was disconnected from one of the heater pins, the tube is new...

[jmartis2]

@ubuntupokemoninc I think you'd better use a resistor... here I would use a 250 watt choke for mercury vapor lamps, but I don't know if you have those there. A resistor will be ok, use a ~20-50 watt resistor that limits the inrush heater current to 40-50 amps, then bypass it after a few seconds.

[ubuntupokemoninc]

@jmartis2

gu-5b, sorry i'm using an on screen keyboard, the heater is 27 amps max @ 12.6 volts. so i can use chokes from high intensity light? we only have CFL bulbs can i use them?

[jmartis2]

@ubuntupokemoninc So which tube do you have? You can use a small variac, or an inductor choke (for HID or fluorescent lamps) as inrush limiter for large heaters. A resistor is OK for smaller heaters, the resistor can be rated at only a fraction of the dissipation it will see - as it's only for a moment.