HP CRT mould update

Bob Shannon bshannon at tiac.net
Sun Apr 17 14:19:16 CDT 2005

Someone on the list asked me to send them samples from my Imlac
restoration.  I've got the email saved here somewhere....

I even bagged up some samples that have not been 'melted off' with
a wire, but I've not gotten them packed to ship just yet (my 'shipping
department has a huge backlog).

----- Original Message ----- 
From: "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
To: "General Discussion: On-Topic and Off-Topic Posts" 
<cctalk at classiccmp.org>
Sent: Sunday, April 17, 2005 2:11 PM
Subject: Re: HP CRT mould update

> On Sun, 2005-04-17 at 10:13 -0700, Vintage Computer Festival wrote:
>> On Sun, 17 Apr 2005, Jules Richardson wrote:
>> > I've just removed the faceplate on the CRT for an HP 250 that was
>> > suffering from the dreaded mould. Used a bit of resistance wire as
>> > someone here had suggested, and it was a remarkably easy job.  Took
>> > about ten mins to make it all the way across the CRT (although I was
>> > only running from a 10V DC supply - I expect there's a lot of scope for
>> > increasing the voltage without risk of damaging the CRT)
>> >
>> > The sealant stuff pretty much just peels straight off the front of the
>> > CRT / rear of the faceplate once the two are separated.
>> Thanks for the info.  Did you save any of the affected scraps to have
>> analyzed by a biologist or something?
> Hmm, nope - but they're just in the bin outside (contained within the
> newspaper on which I was working) so if someone does know someone I
> could retrieve a piece...
>> Are you certain it was a mold eating at the sealant
> Actually, there was no obvious mould as such on this one - it seemed
> more like the sealant had turned to liquid in some places (visible as
> 'puddles' behind the glass), whilst in others it seemed to have
> crystalised into small hard lumps (giving the visible white spots)
> So, no sign of visible mould - I wonder if the dark spots sometimes seen
> are maybe some form of optical effect; trapped bubbles as you say rather
> than being something physically dark in colour.
> Our other HP 250 display shows far more signs of the dark 'mould' spots,
> so maybe I'll give that one a go now that I know the procedure works.
>> > I'm not sure about trying to re-seal it; that could go horribly wrong
>> > and leave air bubbles trapped in there. Not even sure what stuff to 
>> > use.
>> > Padding the faceplace out as necessary right at the edges (where it
>> > won't be visible when everything's back together) is probably the best
>> > course of action and it'll look as good as new when back together.
>> If you don't introduce some sort of filler you might have a shadow or
>> annoying opitcal affect.  Possibly.
> Hmm, good point. Initially I think we're just going for a static display
> anyway, because there are more pressing projects to sort out than this
> machine - so it won't be an issue until someone has time way down the
> line to actually restore the machine to working condition.
> Maybe I should try this same procedure on one of our HP terminals that
> have the same problem though, then I can mess around with fillers on
> those (or see how well it works without).
>> > Next interesting task will be getting the paint off the 250's console
>> > desk though - seems like when they were scrapped someone just went
>> > around with a spray-can and put big X's on anything that was being
>> > disposed of...
>> Gasoline (or petrol as you might want to call it :) is supposed to be 
>> able
>> to dissolve spraypaint without affecting the underlying paint.
> Interesting, I'll give that a try on a test area somewhere - luckily the
> spray painters missed the built-in keyboard area! Mainly worried about
> whatever I use to remove the paint damaging the underlying console table
> material...
> cheers
> Jules

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