[rescue] Old Monitors

[John Hudak]

Just a note about keeping old monitors.
There is a time (and somewhat environmental) issue that will render the CRT
difficult to see possibly making it totally useless despite having good
electronics.

A leaded glass face is bonded to the front of the CRT.  Over time, the
bonding deteriorates and the glass begins to delaminate.
In general, the adhesive used was some sort of thermoset polyester or amide
type compound which is both hygroscopic and biodegradable.
As the delamination occurs, moisture gets trapped and gives rise to
alge-like specs that grow on the inside of the front glass.  Sometimes the
delamination looks like a wave or a dark irregular shape on the glass.
Note that no amount of cleaning is going to make the marks go away.  There
is no (safe and sane) way to remove the glass, clean it, and reattach it.
The CRT is worthless.  It may still perform well, but the user is
constantly looking through the muck that has grown between the glass.

I bring this up because my collection of CRT based things (terminals, test
equipment, and computers) have begun to show delamination.
A Perkin Elmer terminal mfg 1976 came down with the disease about 9-10
years ago.  A Hazeltine terminal circa 1979 showed the blight about five
years ago, my HP logic analyzer, circa 1982 showed the blight  about a year
ago. All of these devices were kept in a climate controlled basement when I
inherited them from their labs - they were not mistreated.
So, extrapolating a bit, if I am seeing failures in gear mfg in 1982, that
suggests a 35 year life span.  Partially substantiated by the failure time
line of my mid 1970s CRTs.  Applying the failure timeline to gear produced
in the late 80/early 90s, they got about 7-10 years of life left... more or
less.
So my points here are:
1. one may be able to fix the electronics but the CRT degradation will get
you in the end. Its unavoidable, like death n taxes.
2. If you use/collect vintage CRT based gear, may want to plan on options
to use something else instead.
I don't know of any way to guard against this failure - of course,  keeping
them in a good environment will help.

I was more than a little bummed when I went to throw my logic analyzer onto
my PDP11 and found that it had the blight...
This has been my experience, friends of mine have seen similar
failures....YMMV.

In many cases you can find donor machines or NOS parts but chances are they
are in the same timeframe
Disposing of CRT based devices in the states has become a royal PITA as
salvagers that take this type of gear are very few and far between, with
fees to process your device ranging from $30 to $100/device.

-J




On Wed, Feb 14, 2018 at 9:30 PM, Mouse <mouse at rodents-montreal.org> wrote:

> >> Seems to me there's a market - a small niche market, but still - for
> >> new CRT monitors.  Anyone looking for a business plan?
> > If I remember correctly there was also an environmental reason why
> > folk moved away from manufacture of CRTs, possibly to do with heavy
> > metals or some such reason?
>
> Possibly; I don't recall any such details, for what (little) that may
> be worth.  It seems obvious to me to take the sync-to-signal
> electronics from a CRT and backend it with a flatscreen, but a friend
> who's much better in touch with such things than I am says that would
> infringe various patents.  (Invalid patents, I suspect, based on the
> obviousness criterion, but, even if I'm right, breaking them would
> require someone willing to slog through the relevant aspects of the
> applicable legal system(s).)
>
> Of course, there may be jurisdictions with saner patent systems where
> there are no such patents, but I suspect that does not describe most of
> the market, thus semi-killing the business plan. :-(
>
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