Prototype set is here

[miniman82]

I have very sad news to report: the proto CRT is dead. I don't know why this happened, it was in operation a few days ago. I came back from Beloit this afternoon and turned it on, only to be greeted with crackling sounds and no picture. Sliding back the neck stuff revealed white getters, and a crack nearly all the way around near the base. This means there's no more proto CRT's left working in the world, and it will be a long time, perhaps never, that one will be seen in operation again.

[Sandy G]

Damn ! Might have been a manufacturing defect that just finally manifested itself...

[Glenz75]

Aw Man that really, really sucks, sorry to hear this news...

[David Roper]

I'm gutted, I can only imagine how you feel. So sorry Nick.

[Eric H]

Oh man, this is terrible news!
We can only guess what went wrong, being a Prototype it was probably run off in a hurry with no thought to it's longevity.

Thankfully we at least got to see it (and document it) operating before this happened.

I wonder if that darker area was the fracture origin point, being on top it would have had the most heat, and stress.

[sampson159]

at least we had it once.sad ending to a great set and a great series of posts

[mpatoray]

Nick,

How sad to see this happen, although it was great to see the picture on it that you did capture of it working properly.

I felt privileged to see it at the ETF, and also privileged to help u that little bit of soldering I learned a lot watching you guys work on it.

Matt

[miniman82]

The only thing I can think of that might have gone wrong is a hot spot on the glass, a consequence of building the tube incorrectly to begin with. If the flames are kept on the glass for too long during an operation like neck welding, the glass becomes very brittle and subject to fracture. This can be seen with a polarimeter, the glass will have a blue band around it. Can't be sure what the cause was, since I hadn't done anything to it between the time it was last used and now. It just sat up here in the apartment, no one even touched it. I suspect this is a fatigue fracture, caused by repeated heating and cooling of the area around the weak glass. The heaters were supplying the heat, and it looks like it gave way at the hottest spot- right above them. If RACS can rebuild this, it would be a simple job. Just neck glass and a gun, but I hesitate because dot plates have broken in the past and these are more fragile than a 15GP22 because the internal structures are different. A 15GP22 has a lightweight frame holding the mask and plate in alignment, and because it's light it gains or looses heat relatively fast. The proto tubes on the other hand have a heavy metal block between the dot plate and mask, meaning they have much more thermal mass. I will have to ask Filipe what he thinks about giving this a go, it's a long shot at best.

[mstaton]

Wow, that really sucks. Sorry to hear that miniman.

[ChrisW6ATV]

I am sad to see this news. I wish you good luck with the rebuilding possibility.

[zenithfan1]

OMG! That is the crappiest news I've heard as far as the tv hobby is concerned. It had such good emissions too I wish I could have seen it working more, I was sick last week with a sinus infection or I'da been over. Crap, I hope you can get it rebuilt at least.

[Steve McVoy]

I wonder if this is related to the convergence problem. Maybe there was a very small leak that still allowed the tube to have emission but messed with the convergence?

[Aussie Bloke]

I am very saddened that your prototype tube has cracked and gone to air, especially the fact the tube was finally up and running displaying good colour pictures , if something like this happened to me with my projects I would be weeping buckets! Knowing RACS having successfully rebuilt a 15GP22 and there being possibility they can do the same with your prototype tube gives some ray of hope and I do hope after your discussion with Filipe it will be agreed that it will be feasible to try getting the prototype tube rebuilt. Anyhow despite the sad news, it was really good that you brought this tube back to life while it was in working condition and got it to display excellent pictures! Anyhow best of luck with whatever possibilities there is to get the tube rebuilt!

[Kevin Kuehn]

Bummer for sure. But thankfully it was slow enough lose of vacuum to not launch the gun assembly forward. Hopefully RACS can rebuild.

[dieseljeep]

Did you leave the air conditioner on
for the weekend? With all these temperature extremes we've been having, it's little wonder other failures aren't occuring.
Third floor apartment and all!