Heathkit GR-900 Build Thread!

[jr_tech]

Originally Posted by N2IXK

I have serious doubts about the safety of tubes that have undergone the standard cat removal procedure. The whole purpose of that resin was to effectively form a glass/resin/glass laminated panel, similar to automotive safety glass. Without the resin layer, it is just an unprotected CRT behind a second sheet of non-safety glass (the reinstalled faceplate). At least the older sets actually used a laminated glass safety panel in front of the unprotected CRT. The faceplates on laminated tubes are just tinted or frosted glass, which would only add to the shrapnel from an implosion if not bonded with the resin.

Obviously CRT rebuilders must have had a way to remove and rebond these faceplates properly when rebuilding tubes, as the resin would never have stood up to oven bakeout. Does anyone know how this was done? It isn't addressed in the excellent film made of HawkEye's rebuilding process over on the ETF site. I imagine that it takes some special setup (like vacuum impregnation) to ensure no trapped air bubbles in the resin. Clear 2 part urethane casting resin is available from several suppliers, and would probably be a good substitute for the PVA that was originally used, if a way was available to get a void-free fill.

In this post, I described a process that I have observed:

http://www.videokarma.org/showpost.p...11&postcount=2

jr

[N2IXK]

Interesting. Thanks for posting that. The PPG number you posted appears to be an automotive paint, not a bonding resin. I have used various products from Forsch Polymer Corp. over the years, and they have a few resin systems that seem like they would work well for this application, with low uncured viscosity and good transparency when cured.

May have to give it a try on a dud tube at some point to see if the cataract problem can be solved without compromising future safety.

[jr_tech]

Originally Posted by N2IXK

Interesting. Thanks for posting that. The PPG number you posted appears to be an automotive paint, not a bonding resin.

I tried to dredge another number out of the old memory cells, but I keep comming back to PPG 5252. Dead cells? Two numbers associated with this task had a nice rhythm, like 5252 and 1418 for the UL crt implosion test document. Wonder if the 5252 number got recycled to another product after the process was retired.

The resin that was used was heated (85 C ?) in small batches and the mek-p catalyst was added and mixed in just before the pour was made. When cured, the resin had a rubbery consistency.

Good luck with your experiments,
jr