CRT peel

[vjp...@at.biostrategist.dot.dot.com]

I bought an HP 2621a CRT computer terminal in 1980. But about fifteen years
ago the screen got black spots like mildew. But it ain't mildew. Apparently
the glue holding a plastic sheet over the glass is decaying. I looked online
and found you have to peal that plastic off and remove the glue. I do have a
Zerox (ok, it was Savin then) copy of the service manual, but it says nothing
about this. Yeah, it's nostalgia and prolly not worth the effort. But would
appreciate any tips from anyone who has done anything like this before.



--
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---{Nothing herein constitutes advice. Everything fully disclaimed.}---

[John Robertson]

On 2021/06/11 7:10 p.m., vjp...@at.BioStrategist.dot.dot.com wrote:
> I bought an HP 2621a CRT computer terminal in 1980. But about fifteen years
> ago the screen got black spots like mildew. But it ain't mildew. Apparently
> the glue holding a plastic sheet over the glass is decaying. I looked online
> and found you have to peal that plastic off and remove the glue. I do have a
> Zerox (ok, it was Savin then) copy of the service manual, but it says nothing
> about this. Yeah, it's nostalgia and prolly not worth the effort. But would
> appreciate any tips from anyone who has done anything like this before.
>

I have not done the process, however I do advise you wear protective
clothing (heavy leather/armoured apron or jacket and gloves) and a full
face shield that protects your eyes and neck when working with picture
tubes. They can be very dangerous, in close quarters, if broken...

John :-#(#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

[Michael Trew]

On 6/11/2021 10:10 PM, vjp...@at.BioStrategist.dot.dot.com wrote:
> I bought an HP 2621a CRT computer terminal in 1980. But about fifteen years
> ago the screen got black spots like mildew. But it ain't mildew. Apparently
> the glue holding a plastic sheet over the glass is decaying. I looked online
> and found you have to peal that plastic off and remove the glue. I do have a
> Zerox (ok, it was Savin then) copy of the service manual, but it says nothing
> about this. Yeah, it's nostalgia and prolly not worth the effort. But would
> appreciate any tips from anyone who has done anything like this before.
>
>
>

Would that be anything like the CRT "cataracts" that tend to plague
older CRTs? I've seen this type of issue clean back to post-war
televisions, possibly earlier. I've seen some that look different from
others.

https://www.youtube.com/watch?v=4zKnRoNc9Q0

[Stephen Wolstenholme]

On Sat, 12 Jun 2021 14:57:57 -0700, John Robertson <sp...@flippers.com>
wrote:

>On 2021/06/11 7:10 p.m., vjp...@at.BioStrategist.dot.dot.com wrote:
>> I bought an HP 2621a CRT computer terminal in 1980. But about fifteen years
>> ago the screen got black spots like mildew. But it ain't mildew. Apparently
>> the glue holding a plastic sheet over the glass is decaying. I looked online
>> and found you have to peal that plastic off and remove the glue. I do have a
>> Zerox (ok, it was Savin then) copy of the service manual, but it says nothing
>> about this. Yeah, it's nostalgia and prolly not worth the effort. But would
>> appreciate any tips from anyone who has done anything like this before.
>>
>
>I have not done the process, however I do advise you wear protective
>clothing (heavy leather/armoured apron or jacket and gloves) and a full
>face shield that protects your eyes and neck when working with picture
>tubes. They can be very dangerous, in close quarters, if broken...
>
>John :-#(#

I worked on a TV production line for a few years. Nobody had
protective clothing. Just occasionally a CRT would implode when it was
lifted out of the delivery box. It was seen as a loss of production
time rather than a potential injury.

Steve
--
http://www.npsnn.com

[Rob]

vjp...@at.BioStrategist.dot.dot.com <vjp...@at.BioStrategist.dot.dot.com> wrote:
>
> I bought an HP 2621a CRT computer terminal in 1980. But about fifteen years
> ago the screen got black spots like mildew. But it ain't mildew. Apparently
> the glue holding a plastic sheet over the glass is decaying. I looked online
> and found you have to peal that plastic off and remove the glue. I do have a
> Zerox (ok, it was Savin then) copy of the service manual, but it says nothing
> about this. Yeah, it's nostalgia and prolly not worth the effort. But would
> appreciate any tips from anyone who has done anything like this before.

Of course the service manual does not mention this, it was either not
known at the time it was made or the service was not intended to cover
that long of a lifetime.

There will likely be other things wrong with it, like dried-out electolytic
capacitors or other components that decay over such a long time.
I would recommend consulting someone with experience in refurbishing
such equipment, like "Curious Marc".

[Lucifer]

On Sat, 12 Jun 2021 02:10:09 +0000 (UTC),
vjp...@at.BioStrategist.dot.dot.com wrote:

>I bought an HP 2621a CRT computer terminal in 1980. But about fifteen years
>ago the screen got black spots like mildew. But it ain't mildew. Apparently
>the glue holding a plastic sheet over the glass is decaying. I looked online
>and found you have to peal that plastic off and remove the glue. I do have a
>Zerox (ok, it was Savin then) copy of the service manual, but it says nothing
>about this. Yeah, it's nostalgia and prolly not worth the effort. But would
>appreciate any tips from anyone who has done anything like this before.

I have a 45 year old CRT colour TV!

[ohg...@gmail.com]

On Friday, June 11, 2021 at 10:10:13 PM UTC-4, vjp...@at.biostrategist.dot.dot.com wrote:
> I bought an HP 2621a CRT computer terminal in 1980. But about fifteen years
> ago the screen got black spots like mildew. But it ain't mildew. Apparently
> the glue holding a plastic sheet over the glass is decaying. I looked online
> and found you have to peal that plastic off and remove the glue. I do have a
> Zerox (ok, it was Savin then) copy of the service manual, but it says nothing
> about this. Yeah, it's nostalgia and prolly not worth the effort. But would
> appreciate any tips from anyone who has done anything like this before.
>
>
>
> --

The CRT is considered a single replaceable component. Removing the bonded safety glass is very dangerous and something no manufacturer would recommend. John Robertson's advice to wear armored clothing and eye protection is a good one if you want to attempt to remove the safety glass. I've used a heat gun and piano wire stretched between a couple of pieces of wood dowel to slice the glue to remove the cataract safety glass, but both the tube and safety glass were indeed glass. If that's some sort of plastic on the HP, I don't know if the same procedure would work.

[John Crane]

Oh yes, this is true. Glass shards are not sent flying everywhere.
It's a very clean neat process and results in a little pile of glass on
the floor. Almost as if someone had swept up the debris!
After the glass breaks, the external atmospheric pressure pushes the
glass pieces into the inner vacuum void. Impressive to watch.

-John

[Michael Terrell]

On Sunday, June 20, 2021 at 9:40:48 AM UTC-4, John Crane wrote:

> Oh yes, this is true. Glass shards are not sent flying everywhere.
> It's a very clean neat process and results in a little pile of glass on
> the floor. Almost as if someone had swept up the debris!
> After the glass breaks, the external atmospheric pressure pushes the
> glass pieces into the inner vacuum void. Impressive to watch.
>
> -John

That's the case with the implosuion shield in place. I've seen cases where early CRTs without one launced the electron gun across the room. In one case, it was stuck in the wall after going through the drywall.
The early, round screen color CRTs were quite dangerous when they imploded, since the bell of the tubee was metal and didn't shatter.