Ethan Dicks via cctalk wrote:
On Mon, Sep 23, 2019 at 4:36 PM steven stengel via
cctalk
<cctalk at classiccmp.org> wrote:
Found a Datapoint 2200 in Austria that I wanted -
I asked seller Viktor to pack it well, by wrapping it several times in big-bubble
bubbewrap, until it was just a giant cube of bubble wrap.
Looks like it was worth it.
Second - what to do about that screen?
As someone pointed out, that looks like "CRT cataracts" - where the
PVA layer between the face of the CRT and the implosion field breaks
down. I've had to fix DEC terminals with this condition (and others
here have had similar experiences on certain devices). There are ways
to get the protective glass off the front. I used a wire to slice
through the PVA. Others have reported using heat guns to soften the
PVA. In the case of the VT220, I needed to put the glass back after
cleaning both surfaces because just the CRT along wasn't thick enough
to fit in the bezel with the original mounting technique. It did
depend on the PVA layer. I found some 3M Silicone Tape (3M VHB Tape
4910?) that was clear and 1mm thick. I just put squares on the
corners but it would likely work if you edged the entire area to keep
dust out of the space between.
I know DEC VT220s and VR201s are prone to this condition and I believe
I've read about ADM 3A terminals with the same. Some terminals use
bare CRTs (thicker face glass, or just manufactured to older
standards?)
-ethan
Just a comment.. such picture tubes with the PVA layer seem to be
completely unusual in the former eastern block countires.
They all used tubes with thick fron glass for implosion protection.
Regards,
Holm
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