I recently bought a 180dmb22(g) tube from ebay for about 25 dollar with rating 7 and large wear pattern just to experiment with.

I connected the tube using the electronics from another tube that had low emission but the electronics worked fine on that tube. Once connected I noticed that the hv power lead was a little less isolated than my other tubes but it seemed like an older model tube anyway (did not have electronic astigmatism with original electronics).

Putting the marquee 8500 on I saw the green tube work with low emission but after a few seconds I heared a spark I think I even saw it looking in the tube and all the tubes went down. I rechecked all the connections with another person, they where all good. Powered it up again and now it sparked right away. Okay I put the old tube back in and no damage was done. So with a few hartbeats I got away with it but what might have caused this sparking? Is it possible that this tube was for an 8500 with lower high voltage?

If it hit spark in tube neck, it's propably some debris in gun assembly that cause short. It's not so rare when tube have been shipped or removed.

It might loose when tube neck is tapped gently or it could need be plasted with tube conditioner.

anode lead

http://www.avsforum.com/avs-vb/showthread.php?t=1135323&highlight=marquee+high+voltage+anode+lead

anode lead

http://www.avsforum.com/avs-vb/showthread.php?t=1135323&highlight=marquee+high+voltage+anode+lead

Thnks for the answers! Seeing this picture is indeed how the anode lead looks compared to the 'old' tubes.

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=138780&d=1238866748

Is it possible to take the anode lead from another tube and exchange them?

Is it possible to take the anode lead from another tube and exchange them? yes, but it's a little tricky. I would try simply cleaning and filling the old loose fiting boot first with RTV.
If you have a newer style lead with the clear silicone sleeve then Use a very sharp exacto knife and work it around the boot. Don't use too shallow of an angle with the knife or it will slice the boot.It's better to angle the knife down towards the glass and only go in 1/4 inch at a time. Go all the way around and then work your way in towards the center.

I bet it just needs a good knocking while its running as crud might have shifted to the guns from the front of the tube, all my used and some new tubes have showed this.
had the same issue with a shut down and initialization. onec i got it to stay on I was able to knock the tube neck and watch the fireworks inside the tube neck, very cool.

Athanasios

I bet it just needs a good knocking while its running as crud might have shifted to the guns from the front of the tube, all my used and some new tubes have showed this.Athanasios true, fox should clarify if the "spark" was a flash inside the tube or a loud crack-snap noise on the outside of the tube. If it was a loud snap outside then it's a HV leak. If it's a flash inside the tube then it's crud on the gun.

I think I saw some light sparking through the fosfor so it might very well be inside the tube as suggested. I will check both suggestions, I'm glad I asked because I allmost threw the tube away :)