Removing PVA from a CRT

Alan Perry aperry at
Mon Nov 19 19:28:44 CST 2018

In the video that I looked at, the guy cut 8 1/8" pieces of double-sided 
foam tape, three each along the top and bottom and one on each side, 
then sealed it with clear packing tape. It seemed to me that using some 
optically clear adhesive sheet would accomplish both jobs.

I have some heat pads (gel in plastic that gets thrown in a microwave to 
heat up) for loosening the screen adhesive on iPads and such. Can I use 
them to get the remaining PVA to loosen up?

On 11/19/18 1:10 PM, Cory Heisterkamp wrote:
> Those retrace lines are likely an artifact of the brightness control 
> being set too high. It's pretty typical with older monochrome TV sets. 
> It also looks like there's insufficient vertical sweep, probably due 
> to old capacitors.
> On a CRT that small, I wouldn't be concerned about direct fitting the 
> safety glass over the CRT. In fact, if it has an implosion band, that 
> outer glass could possibly be for glare reduction only. Some TV 
> collectors use foam tape around the perimeter of the CRT face as a 
> cushion, then seal the glass to the face with a good quality tape.
> The good news is that PVA is so bad that an hour soak in a tub of warm 
> water should do the trick. -C
> On Mon, Nov 19, 2018 at 3:02 PM Alan Perry via cctech 
> <cctech at <mailto:cctech at>> wrote:
>     On 11/19/18 12:18 PM, Warner Losh wrote:
>     >
>     >
>     > On Mon, Nov 19, 2018 at 11:41 AM Alan Perry via cctech
>     > <cctech at <mailto:cctech at>
>     <mailto:cctech at <mailto: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?
>     >
>     >
>     > Pics?
>     Here is an attempt to use Facebook for image hosting here. If it
>     doesn't
>     work, I will put the image up on a real image hosting site.
>     alan
>     >
>     > Warner

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