Invisible crt getter?

[SwizzyMan]

So my Labor Day vacation turned into a TV hunt. I picked up a beautiful admiral with a 20B1 chassis and a phonograph. I didn't take my crt tester with me to Daytona where I am spending my Labor Day weekend. So I immediatly took out the crt to look at the getters. I don't see anything in the getter window all I can see is a rainbow like effect on the side of the getter window. This tube was a rebuilt 12LP4, could the tube still be under vacuum? Will start a restoration thread on this set once I get it back home and find out whether the crt is still under vacuum.

[Username1]

I don't think those tubes have vacuum problems.... Although there may be that one.....

.

[miniman82]

I have a couple 12AU and AX7's with getters like that, they would fine. I suspect they weren't completely flashed, if there were a problem with the vacuum you would see white instead.

[Eric H]

I've had some like that that still worked just fine.

[old_tv_nut]

Curious - could the getter be further up in the funnel and not visible in the usual place?

[Username1]

If a getter was not fully fired, and a tube gets weak, can it be fired again....?
Can the cathode be put through the activation process again...? Anyone at etf
tried experimenting on some dud tubes...? Something that should be looked into...?
Especially on rebuilds that may possibly have had less than perfect procedures...?

.

[Eric H]

Some, or maybe all of the 10 & 12 inch round tubes have a getter in the neck, and another in the funnel near the Anode. Sometimes there's a window where it's visible, or maybe it's only visible when the Dag coating has flaked off.

[SwizzyMan]

OK tube has not gone to air. But is tired. Is it OK if I let it cook at about 8 volts all night?

[Eric H]

Originally Posted by SwizzyMan

OK tube has not gone to air. But is tired. Is it OK if I let it cook at about 8 volts all night?

That's too long at that voltage, if it hasn't improved in 5-10 minutes it probably never will.

[Username1]

I use to run weak rca color tubes at high fil. voltage and brightness all the way up
for a few days, and it would improve the tube.... I also use to hit them with a stick
on the neck lots a snapping in there... I guess it was just burning off the carbon....

If it's a weak tube, you don't have much to loose, I wouldn't go much above what a
brightner would put out though.....

When you say you run the fil. at 8V, is it just the fil. or is the tv on with the tube
having cathode current flowing...? And not P@@@ current, full brightness,
retrace lines as bright as the scan lines.... I can't see just a high fil. voltage and no
current flow as making a difference...? Heating up the cathode with current flow
is the only thing that comes close to the activating kinda thing it went through
at birth..... I figure that's how I got life outa the tubes I cooked years ago....

.

[Bill Cahill]

I've got a rebuilt used 16GP4 that I tried cooking three times, with an hour separating them shut off. Every time, Tube takes a long time to show anything. It slowly sneaks up in the red, then, after about five minuites, barely goes into the green. It's definitely tired out. Came with a combination RCA Victor tv I own.

[timmy]

i think if there is an invisable getter present then i think its safe to say that when fired it was there but gassey and other things that may go wrong with a crt may have taken several factors away from the getter where it no longer looks the way it should. but of course air would have turned it white. i have a sylvania 7jp4 with such a getter, can bearly see anything aside from what looks like a rainbow as a getter and the tube bearly shows a pic in the dark. some would think that there are still people around that was there in the day building these tubes and know what is what when it comes to these questions regarding crts but then again they may be up in age and not be able to recall all the info that may be asked of them. so i guess we are left to guess or assume what may be or not be wrong with a given crt, either way we are left with what we have working or not and may never be able to get a crt rebuilt to the degree of standing up and lasting longer then the set it self.

[kramden66]

Bill that 16gp4 doesn't show an image when the set is running?

[SwizzyMan]

Hmmm when I let it sit at 7 volts it would produce a nice picture. Maybe a brightener would be an option?

[Phil Nelson]

I would restore the TV and see how it looks. Sometimes tubes that don't look so hot on a tester produce an acceptable picture. Testers are good for identifying gross faults in tubes, but they don't tell the whole story.



Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html