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.... How do you manage getting THAT kind of a screen burn?
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faustian.spirit <faustian.spirit@...>
130521489871
speechless.
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Don Black <jeans@...>
I guess it stood ready and waiting for the call to duty for many hours.
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Back in the late sixties at the university I worked at in the AVA department we got sent a vidicon tube and asked to fix it. This was when lasers were the new toy and the physics department had been experimenting with them. obviously they had used the vidicon to observe the laser beam, either directly or through some optics and it had nicely evaporated the photo surface off the faceplate with a 2:1 Lissajous figure. You didn't have to operate it, the burn was clearly visible just by looking at the tube. It makes this burn look like a mosquito bite. We just said "sorry" and gave it back to them. Don Black.
On 20/05/2011 5:38 AM, faustian.spirit wrote:
130521489871
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Albert LaFrance
The worst screen burns I ever saw were on IBM “green screen” CRT terminals (3270-series) used as operator’s consoles on mainframe computer systems back in the 1980s. Portions of those tubes sometimes displayed text that would remain unchanged, sometimes 24/7, for years on end. And they were usually running at high brightness due to the lighting levels in the computer room.
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of Don Black
Sent: Thursday, May 19, 2011 8:52 PM To: TekScopes@... Subject: Re: [TekScopes] .... How do you manage getting THAT kind of a screen burn?
I guess it stood ready and waiting for the call to duty for many hours.
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faustian.spirit <faustian.spirit@...>
Well, guess the vidicon would make a good monoscope if you have any use for a figure eight ;)
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But won't any evaporated phosphor or photoconductor mess up the vacuum far in excess of what the getter can take? In case of the 585 tube I wonder whether the phosphor has just been chemically altered and discolored, or whether it is actually gone from the screen. Is the intensity vs focus/trace width on a 585A tube much different from what I know from the 545B (while you can dial in a blinding brightness there, you will dial it right back in normal operation because the trace becomes hideously wide if not viewing something of very low repetition rate)? ... I was reminded to post this when seeing the picture in 61954 (2235 w/ intensity control problems, I am aware these are not the operators fault. Looks like there is already phosphor damage at least under the left end of the center graticule line, if not under all of its length. That level of perceived brightness under conditions of bright light shining on the front panel would make me *leap* for the intensity knob But then I have probably gotten too cautious from having two ASOs as my current main bench machines :) . Or does the photography really make it appear far brighter than it is even under the fault conditions described?
--- In TekScopes@..., Don Black <jeans@...> wrote:
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Brad Thompson <brad.thompson@...>
On 5/19/2011 9:19 PM, Albert LaFrance wrote:
The worst screen burns I ever saw were on IBM �green screen� CRTHello-- IIRC, the pumpkin-orange phosphor used in some monochrome CRT displays circa 1975-1980 was also extremely susceptible to screen burns. Which brings to mind another anecdote: I worked for a company that built industrial controllers and automated-visual inspection systems that included small CRT displays manufactured by Ball Bros. Research. As a cost-reduction measure, someone in Purchasing bought some Chinese-made displays that were inferior and would have led to order cancellations, had we not replaced them with the original displays. I pointed out that it was the first known instance of the Balls having someone by the customers. My manager was Not Amused...<g>. 73-- Brad AA1IP
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mileschuck59
Don, this is a little OT, but Tektronix had a mod kit (p/n: 040-0159-00) that is easy to install and limits how bright you can set inten control. I have added one to my 545B and others,... saves nicely from burns. Chuck
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--- In TekScopes@..., Don Black <jeans@...> wrote:
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David Holland
Details on said kit? and how hard it would be to replicate manually?
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I have a couple of 500 series tek scopes now that it may not be a bad idea to protect them... thanks, David
On Fri, May 20, 2011 at 1:04 PM, mileschuck59 <chuckhmiles@...> wrote:
Don, this is a little OT, but Tektronix had a mod kit (p/n: 040-0159-00) that is easy to install and limits how bright you can set inten control. I have added one to my 545B and others,... saves nicely from burns. Chuck
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faustian.spirit <faustian.spirit@...>
I also wonder whether they made something to replace the coin-operable case locks for educational settings, IF 500 or 7000 boxes were ever used in such settings, and IF it wasn't assumed that high voltages inside would educate and examine the student in a far more practical way ;) I am not a teacher (which is good QED), but if I was nowadays I'm afraid I'd be virtually required to disconnect some of the outputs and padlock the case shut on a 5xx used in class...
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With low rep signals, the high intensity reserve of a 545B certainly rocks - split microsecond edges of kilohertz square waves... but then you make certain the tops of the square are and stay well offscreen! ... low rep users, independent of perceived brightness, might be a different matter...
--- In TekScopes@..., "mileschuck59" <chuckhmiles@...> wrote:
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David Gravereaux
On 05/19/2011 07:29 PM, Brad Thompson wrote:
On 5/19/2011 9:19 PM, Albert LaFrance wrote:The worst screen burns I ever saw were on IBM “green screen” CRTHello-- Here's a fun example of burn-in. Got permission to finally replace the green-screen (P31?) CRT in our old H/P 8924C RF test set and luckily took a comparison picture for posterity. This dates back to around 1985. So that's many, many hours of use. -- David Gravereaux <davygrvy@...>
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