Interesting ION issue

[DZ]

I'm having an interesting ION issue and I can't come up with a good reason for it. It's a Reliant 300WC with around 160 hours. The head was last serviced in 2007, originally manufactured in 2003. When it first starts it has a great color balance though it does lean a bit red. If I let it run for 6-8 hours at around 9-10 amps it will shift largely to red, leaving the other lines very weak. If I turn it off for 6-8 hours and then turn it back on, it again starts with a relatively nice balance, then shift red within about 30 minutes. If I leave it off for a couple weeks I can get a good 6-8 hours at 9-10 amps before it shifts red again.

When I say it shifts red, yellow is almost completely gone, the 2 green lines are both very weak and with a semi strong blue line. To me, from reading thru the laser FAQ, this would indicate high krypton pressure, but why start with such a balance of color only to shift to high krypton pressure with use. I'm not understanding why the Vdrop is going up unless maybe there's a contaminant in there or perhaps I just need to run the hell out of it to get the krypton down.

If it helps, at 9amps tube voltage is around 180VDC when the colors are balanced. When it's shifted red the tube voltage is around 193VDC. When this occurs I have ramped the current up to max, 12A, and the voltage drop went up to 205VDC.

[mixedgas]

Your cathode is spongy and is releasing gas. If the blue is 482 or 488 You have the "Red Blues". What is suprising is how long it takes to degas, yet how qucikly it re-adsorbs. Check the cathode voltages. Does this one have a third pin for a getter? See if one end of the cathode meters to the end bell through a tiny fraction of a ohm.
That is the other getter location, welded from the endbell to a lead.

Steve

[DZ]

Your cathode is spongy and is releasing gas. If the blue is 482 or 488 You have the "Red Blues". What is suprising is how long it takes to degas, yet how qucikly it re-adsorbs. Check the cathode voltages. Does this one have a third pin for a getter? See if one end of the cathode meters to the end bell through a tiny fraction of a ohm.
That is the other getter location, welded from the endbell to a lead.

Interesting, so does that indicate to you a poor job of reprocessing of the tube back in 2007? Guess I'll be using a different company, though not many are left, are there? Cathode is about 2.7V, no 3rd pin for the getter. Neither end of the cathode has continuity to the end bell.

[Zorched]

I would not say that is poor reprocessing. It sounds like a cathode aging issue. Did it work as planned when reprocessed?

Z.

[DZ]

I would not say that is poor reprocessing. It sounds like a cathode aging issue. Did it work as planned when reprocessed?

Z.

Welcome to PL, Zorched. Well, I don't know if the cathode was replaced in 2007, if not, then it's a 9 year old cathode with less than 200 hours on it, of which at least 100 of the hours were at idle current. I talked to a tube reprocessor and they don't think it's a cathode issue, more of a reprocessing issue back in 2007. Aparently, it was either not baked hot enough or long enough to burn out the gasses trapped in the tube walls. So when the tube gets hot the gasses start to release, not just from the cathode but from the BeO as well. Which might explain why it happens so quickly and recovers so quickly. So ultimately this thing has a date with a reprocessor, but it's going to have to wait until after Halloween! And probably wont happen until next year.

[Zorched]

Was this the reprocessor in Ohio who thinks he should not use tube ovens and heat tapes? Plasma processing alone is not enough.

Something else in the tube has to be spongy, once gas is in BeO, it is very much a one way trip. A weld, the cathode matrix, some left over brazing flux etc

Z.

[DZ]

Something else in the tube has to be spongy, once gas is in BeO, it is very much a one way trip. A weld, the cathode matrix, some left over brazing flux etc

So in other words it was poorly reprocessed, which is why it wont go back to the same place as before. Who is this anyway, why are you hiding behind a newly registered screen name that is creepily similar to my last name............

Was this the reprocessor in Ohio who thinks he should not use tube ovens and heat tapes? Plasma processing alone is not enough.

I wont confirm nor deny the answer to this question. I actually communicated with 2 different reprocessors, one of which I've done business with before and the other came highly recommended by an old friend.