I have a tube that I can't identify and I'm hoping someone can help. The only ID I can find is the number 488. Maybe a Westinghouse? I tested it as a 50 on a Triplett 3413 tester, and it's gassy with a purple glow inside the mesh, but I let the filament run for a while and the glow diminished. I'll run it some more today and see what happens.
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The WE-252A looked like this also... Some had mesh plates.
I have a 50 from RCA with that shape of bulb, without the glass neck at the base, and the plate is pressed and square.
T
I have a 50 from RCA with that shape of bulb, without the glass neck at the base, and the plate is pressed and square.
T
Given the gassy state,
It will be nice to know the tube type, so you can put a label in front of it for your Tube Museum Display.
Do not feel bad. I bult a stereo 45 amp ready to go to VSAC (Vacuum Tube State of the Art Conference).
Sounded Great!
The next morning one of the 45s glowed like that, and oscillated. I did not have a spare 45.
So, 2 days before VSAC, I rebuilt the amplifier to use 4-65A Tetrodes (screens used as plates, and the real plates grounded). Whew, what a lot of effort to make the conversion.
It will be nice to know the tube type, so you can put a label in front of it for your Tube Museum Display.
Do not feel bad. I bult a stereo 45 amp ready to go to VSAC (Vacuum Tube State of the Art Conference).
Sounded Great!
The next morning one of the 45s glowed like that, and oscillated. I did not have a spare 45.
So, 2 days before VSAC, I rebuilt the amplifier to use 4-65A Tetrodes (screens used as plates, and the real plates grounded). Whew, what a lot of effort to make the conversion.
I've left it cooking all day (filament only) and on testing the purple glow has diminished, though not entirely gone. It doesn't peg the meter now.
You may be able to get rid of the gas by getting some plate dissipation going.
You would need a variable plate supply.
Configure the tube as basically a diode with the grid tied to the filament. Slowly increase plate voltage and back off if you get gassing. Only run plate current within reason for the tube also.
I have been able to clear some transmitting tubes that way,
You would need a variable plate supply.
Configure the tube as basically a diode with the grid tied to the filament. Slowly increase plate voltage and back off if you get gassing. Only run plate current within reason for the tube also.
I have been able to clear some transmitting tubes that way,
Running without plate current could poison the filament and reduce or eliminate emission. I have been told that baking in an volume at 250F or so might be effective.
The other option is to run at low plate voltage and current, if it gets hot enough the getter may do the rest.
If this is a 50, in circuit grid resistance to GND should not exceed 10K even with autobias IMVLE. (GND to filament as suggested above.)
Plate voltage <= 450V and plate current of ~55mA in a healthy 50, start with much less voltage and watch the current.. Since it is a mesh plate rated dissipation is probably a bit lower than in the 50. I would probably keep this to 15W or so until you know more about the tube.
Even with this intervention it is likely the case this tube is living on borrowed time.
The other option is to run at low plate voltage and current, if it gets hot enough the getter may do the rest.
If this is a 50, in circuit grid resistance to GND should not exceed 10K even with autobias IMVLE. (GND to filament as suggested above.)
Plate voltage <= 450V and plate current of ~55mA in a healthy 50, start with much less voltage and watch the current.. Since it is a mesh plate rated dissipation is probably a bit lower than in the 50. I would probably keep this to 15W or so until you know more about the tube.
Even with this intervention it is likely the case this tube is living on borrowed time.
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I'll set something up and give this a try. As you said, it's likely dead, so it won't hurt to try.