10fp4 purple glow

[tvdude1]

I have a 10fp4 that when tested on my crt tester, shows a slight purple glow when tested for emissions. My question is this tube leaking or just tired? I want to send it to Hawk Eye but not if it leaks. I did not think glass crts leaked.

[jr_tech]

How do the getters look...Nice and silvery?... Thin enough to read a newspaper through?... White? Does the whole gun light up purple, or just between the elements where the beam is passing? How does it test for emission?

I think that every tube leaks, but glass tubes leak very slowly. Likely spots are where the wires pass through the glass, and perhaps around the HV button. When you re-gun the tube, you get new feed throughs at the base, and as a precaution, a little VacSeal or diffusion pump oil around the HV button can't hurt.

jr

[Eric H]

How does it test? Is it on the inside surface of the glass or between the elements?
I've seen a surface glow too on some CRT's. I don't think it hurts anything as long as it's just on the glass.

If the tube is leaking it's most likely through the base, which would get replaced during the rebuild process.

[tvdude1]

Only glows when you push test button and its in the center of the gun only. It glows the size of a match head.

[tvdude1]

Also no emissions at all.

[jr_tech]

Originally Posted by tvdude1

Also no emissions at all.

Hot Shot it? It sounds like you would have nothing to loose by running the heater for a few hours at 8 volts (or so) then re-testing.

jr

[tvdude1]

Will try it.

[jeyurkon]

It does sound gassy. I have a test CRT that does that but it still works. I don't think the test CRT has a leak. There's a burned spot in the center where it was powered up without sweep and I think the gas came from that.

I agree that you have nothing to lose by running it at 8 volts for awhile. If it does recover you might not have the best focus.

John

[Eric H]

Sounds like it's gassy.
Can you put it in a set and apply the high voltage? If it's badly gassy the whole neck should glow purple.

[Reece]

Found this note from "6AU6" over on ARF, he's talking about receiving tubes, FWIW:

"The bit with the magnet is a good test to differentiate between normal cathode rays and glowing gas. If the glow moves around in response to the magnet - it's just good old cathode rays. If it stays still, it's gas (burp)."

[tvdude1]

Left in on 8 volts for 3 hours and rechecked for emissions, well no ones home.Will hunt down another tube.

[leadlike]

If it helps, every crt I've ever tested on my Sencore would make the ion trap magnet give off a small purple glow during the emissions test.

[Eric H]

In any case don't toss it, a 10FP4 would be a good tube to get rebuilt!

[bandersen]

I've got a 10FP4 on it's last legs and have been considering a rebuild. I hope to scrape up the dough soon.