On Wed, 29 Oct 2003, Joe wrote: This does raise an interesting point: why are some CRTs susceptible and not others? Poor quality control? What kind of mold is this anyway? And what the hell is it feeding on? Based on what I know makes up a CRT, it must be some mutant radioactive strain of mold that is probably not to be trifled with. -- Sellam Ismail Vintage Computer Festival ------------------------------------------------------------------------------ International Man of Intrigue and Danger http://www.vintage.org [ Old computing resources for business || Buy/Sell/Trade Vintage Computers ] [ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]

At 09:13 AM 10/29/03 -0800, Sellam wrote: I doubt it. More likely the type glue/adhasive that they use to bond the safety glass on with. What kind of mold is this anyway? And Perhaps that's why we haven't seen Steve on the list for awhile! :-/ Joe

The older HP scope tubes (and, in fact, all the ones for scopes up to the digital models, as well as the electrostatic deflection graphics displays) were made in the tube shop at HP in Colorado Springs, so the tube construction process was different, as HP made them internally (HP was known for quality construction at that time...) If I recall correctly, HP bought the magnetic deflection displays for terminals from a 3rd party... Probably got them all (Calculator displays 9835/9845 and 264x terminal displays) from the same company, though they were made by different divisions... Bill "it" below refers to mold between the safety glass shield and the tube surface... Joe wrote:

On Wed, 29 Oct 2003, Joe wrote: I suspect that it is more a function of who produced the tube. I have a DEC VR201 that also has the same problem. - don

On Wed, 29 Oct 2003, Bill Sudbrink wrote: I also have an ADM 3A where this has happened. In fact, I might have two like this. I wonder if it's a specific brand of CRT? -- Sellam Ismail Vintage Computer Festival ------------------------------------------------------------------------------ International Man of Intrigue and Danger http://www.vintage.org [ Old computing resources for business || Buy/Sell/Trade Vintage Computers ] [ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]

I suppose many will think this is cheating and that it doesn't really address the problem, but I know where there are quite a few of these terminals available that I imagine will eventually just be junked. I'd suggest just getting one of them for parts to fix your terminal Jay. Meanwhile, let the repair procedure debate flow. regards, Dan Cohoe

Jay et al-- I originally posted this back in Sept last year- in reponse to a query from Steve L I think-but the subject line was not all that revealing if you went back thru the archives. ******* Subject: Re: Nifty Find - HP2644A Steve et al This sounds like the problem I had a month or so back with the CRT in a HP9845. Only in my case the mould spots had 'advanced' inwards from the edge of the screen around 2-3 inches. Not pretty! If you have a look you will probably find the 'seal' around the edge of the front of the tube is taped over- virtually no real moisture barrier at all for what is underneath. Further- you will almost certainly find that the front of the tube itself has a conventional bonded safety glass- the mould is in the layer of transparent 'goo' used to attach an additional anti-glare 'cosmetically appealing' dark glass to the front of the safety glass on an ordinary CRT. The 'goo' in the case of the 9845 CRT was very similar in texture to silicon rubber-possibly was- and the layer was a bit over an eighth of an inch thick. Likewise the dark glass on the front. (The I tried several solvents on the 'goo' (after removing CRT from 9845 of course!) and found ordinary petrol to be fairly effective- there are no doubt better solvents but it worked. Judicious use of a piece of piano wire and weights was tried, with the CRT mounted in a temporary wooden frame, but the most rapid way to get the goo out was (you are outside or in a well ventilated area - right!) to dribble a generous amount of petrol into the goo- wait about a minute, and carefully dig out the softened stuff with a long thin screwdriver. It's tedious work and I did it in several stages but it was not difficult. End result- cleaned 'em up and got a perfectly useable CRT and separate 'anti glare' glass. I reassembled them with an air gap and 'goo' in the screen corners only- its easy enuff to get into the gap and clean it out now- should the need arise again. Visually no difference- except maybe a bit brighter screen image. Essential point to note- make sure the tube has a bonded safety glass-- in this case it was difficult to actually tell till I had it out and removed all the black tape around the edge of the screen. DaveB Ch Ch NZ ----- Original Message ----- From: "Jay West" <jwest(a)classiccmp.org> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk(a)classiccmp.org> Sent: Thursday, October 30, 2003 2:55 AM Subject: Re: HP 262x terminal help sought