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VT520 Plastics Crumbling to Pieces

Alegend

Alegend

Experienced Member
Joined
Jun 13, 2017
Messages
88
Location
Israel
I know there is not much that can be done, but perhaps this post could serve as a wake-up call for anyone in possession of a VT520 CRT terminal.

My 1995 vintage VT520 was sitting on a shelf, when a couple of months ago it developed a nice, full crack on the bottom right corner of the front frame.
It was not dropped, hit, or even touched.
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I decided this would be an easy Cyanoacrylate fix, and put it on my mental to-do list.

Yesterday, the thing developed another full break, this time across the top left corner. No touching, no dropping, nothing.
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I moved the terminal ever so slightly for a photo shoot, when the top right corner disintegrated.

Spreading the parts on a flat surface for another photo shoot, a snap snapped, then one of the delicate internal plastic protrusions came off with zero force.
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I own several older VT320 and VT420 terminals, none of them has become crumbly (yet). Perhaps this has something to do with the presence of UL-94-V0 anti-flammability additives.

Interestingly, the affected part is only the front frame. The body of the VT520 apparently is of different composition, is a slightly different color, and is not crumbling.

This VT520 (unlike any of my other ones) has a known history and was never stored in a barn or on a beach. Always kept indoors.

It is too late for this front frame. I think if nothing else, dipping the entire thing in conformal coating lacquer several years ago would have stopped whatever was gassing its way out of the plastics from escaping. Leaving the thing untreated has very poor prognosis.

-Alon.
 
I have had it for 14 years, and it was kept and used in an office environment before that... It had one overseas move in a shipping container, not different from the same trip all gear from Taiwan has had at some point before it reached its destination.
 
As I've posted before, coating the thing probably would have accomplished little. Museums struggle with this constantly, with no solution yet in sight; storing at very low temperatures seems to be the only way to slow the deterioration.

I once owned an Apple monitor that spontaneously disintegrated, dropping bits off the case even though never being touched or powered on.
 
Chuck(G) said:
As I've posted before, coating the thing probably would have accomplished little. Museums struggle with this constantly, with no solution yet in sight; storing at very low temperatures seems to be the only way to slow the deterioration.

I once owned an Apple monitor that spontaneously disintegrated, dropping bits off the case even though never being touched or powered on.
Click to expand...

I have the same problem with an old Apple monitor. Just picking it up, you hear plastic snapping and cracking.
 
tradde said:
Did you actually read the entire first post? He answered your questions.
Click to expand...

Yes,

This VT520 (unlike any of my other ones) has a known history and was never stored in a barn or on a beach. Always kept indoors.

Being stored indoors doesn't mean indoors was climate controlled.

In an attic or garage may be considered indoors.
 
Plastic will be plastic. I had a fairly inexpensive stereo PC speaker set placed on a computer hutch shelf, and it was there for maybe 15 years or longer. Then one day it just crumbled. The knobs fell out of one speaker and the other just fell apart when I picked it up. The speakers themselves and the wiring still looked pretty good.
 
Chuckster_in_Jax said:
Yes,

This VT520 (unlike any of my other ones) has a known history and was never stored in a barn or on a beach. Always kept indoors.

Being stored indoors doesn't mean indoors was climate controlled.

In an attic or garage may be considered indoors.
Click to expand...

Not always climate controlled. Although I believe controlling the climate is only good for delaying the crumbling by a few years at most. Plastic does not turn into aluminum (or stone).

3D design of such a large and complex part, curved along two axis and with lots of detail, is going to be quite expensive. Perhaps using a good part as a reference to make a silicon mold would be a better option. Still would be expensive to cast just a couple of ABS parts this way.

-Alon.
 
Update (not a solution)

Update (not a solution)

Alegend said:
Not always climate controlled. Although I believe controlling the climate is only good for delaying the crumbling by a few years at most. Plastic does not turn into aluminum (or stone).

3D design of such a large and complex part, curved along two axis and with lots of detail, is going to be quite expensive. Perhaps using a good part as a reference to make a silicon mold would be a better option. Still would be expensive to cast just a couple of ABS parts this way.

-Alon.
Click to expand...

I have consulted a colleague that does plastics molding for a living.
Cheapest option is to 3D scan a good part, then proceed with some manufacturing technology of choice - CNC, SLA, or create a mold for a polyurethane part.
Some details of the frame can be omitted as it is not going to be an injection mold like the original.
Still it is a large part, and the on/off pushbutton is an additional part. It is easily a US$1K job maybe more. Unlikely it will be the right shade of beige, so then needs to be painted.

It is cheaper to buy a complete, non-crumbling, used VT520. Then better keep it in a freezer.
-Alon.
 
Just to add a little levity to the sad situation, I offer the lyrics of an old Shel Silverstein ditty:

Plastic
Song by Shel Silverstein

Now a little bitty termite, he come knockin',
Knockin' at my front door,
He walked right in, sat right down
Started nibblin' on the kitchen floor
He chewed on the walls and the ceilings and the halls
Lord knows he tried
But he kept a-gettin' thinner
And he never got no dinner
And finally he sat up and cried

He said, "It's plastic, good Lord, it's plastic!
I know it ain't no wood
And it can't do me no good,
Because it's plastic -- and you can't eat plastic,
Everything's gonna be plastic by and by!"

Then one afternoon in the month of June
I went down to the beach.
There were cuties and beauties in little bathin' suits
And all of them within my reach.
Then a 38-24-36 miss just happened to be passin' my way.
I said, "Please don't think I'm nervy, but you look so very curvy
Please tell me how you got that way!"
She said, "It's plastic it's only plastic,
It's pretty as can be, but you know that it ain't me,
Because they're plastic, oh yes they're plastic,
Everything's gonna be plastic by and by."
 
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