Reforming caps and CRTs

Rod Smallwood rodsmallwood at
Thu Apr 23 03:44:47 CDT 2009

I have two DEC VR201 mono monitors.
They both had the blue spot particularly at the edges.
The spotting exists within the adhesive that bonds the outer faceplate to the screen. The layer of goo is quite thick. (About 2-3 millimeters)

The result is something akin to a car shatterproof windscreen. The extra faceplate is not part of the original tube spec and would have been added by DEC later. I simply prised off the front faceplate in bits knowing it would not shatter as it was stuck to the goo. Peel off the goo on the screen, clean, adjust the cutoff pot and the result is a bright clear display. (Don't try this if you are not comfortable working with CRT's) 
There is a small gap between the bezel and the tube (extra cooling?) but the rubber tube spacers mean nothing is loose.  
Rod Smallwood

I collect and restore old computer equipment with this logo. 

-----Original Message-----
From: cctech-bounces at [mailto:cctech-bounces at] On Behalf Of Jules Richardson
Sent: 22 April 2009 20:25
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Reforming caps and CRTs

Gordon JC Pearce MM3YEQ wrote:
> Nope, I've never even seen this "screen rot" on any tube.  Maybe we
> don't get it in the UK?

I've seen it on lots of HP terminals in the UK, and there's also a Digico 
terminal at Bletchley which has a very bad case of it.

I don't remember ever seeing it on Tek / Apollo / Sun / SGI / DEC / Acorn 
displays, PC monitors, or low-end 40/80 column displays for vintage home 
micros - maybe it'd be possible to narrow it down to a specific manufacturer, 
model range or whatnot...



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