Removing PVA from a CRT

Warner Losh imp at
Mon Nov 19 14:18:22 CST 2018

On Mon, Nov 19, 2018 at 11:41 AM Alan Perry via cctech <
cctech at> wrote:

> I recently picked up a Rainbow 100. The PVA between the safety glass and
> the CRT on VR201 that came with it has broken down and failed badly.
> I have seen videos and read about removing the safety glass, cleaning out
> the PVA, and reattaching and resealing the safety glass.
> All that I have seen basically sticks the safety glass on at its edges and
> leaves a void where the PVA had been. It seems to me that the PVA was
> providing some implosion protection. Would it work to replace the PVA and
> attach the safety glass to the tube with an optically clear adhesive sheet?
> I have seen that this exists, but have never used it before.
> Also, I have never worked on a CRT before. I am trying to find a local
> person who can observe me and stop me from doing something stupid. If I
> can’t find someone, what am I more likely to do wrong? How can I be sure I
> discharged it before touching it?

I have a VR201 that's like this myself, and I've been too scared to try to
fix it. Instead, I've tried bodging together various hacks to try to get
the signal into a modern composite to VGA converter...

Finally, a VR201 specific question. I booted the Rainbow over the weekend
> and, looking through broken-down PVA, I could see the Rainbow has booted
> and I could enter DOS commands. I could also see white retrace lines. What
> is the likely cause of that on a 35-year-old CRT?



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