Forgotten graphics technology: the wild workings of the direct-view storage CRT - Page 1
Forum section: electronics / general

author: BrianHG
author_rank: Super Contributor
timestamp: December 11, 2024, 05:55:54 pm
content: I never knew how my old analog CRT Tektronix storage scope held its image on its CRT.Now I see the trick...

author: TimFox
author_rank: Super Contributor
timestamp: December 11, 2024, 06:22:45 pm
content: Back in the 1970s, I used Tektronix and -hp- storage CROs, and specialized "scan converter" storage CRT devices before "frame grabber" memory-based systems were availableHowever, I have no nostalgia about that antique technology.

author: coppice
author_rank: Super Contributor
timestamp: December 11, 2024, 06:30:14 pm
content: Its only in the last 10 years that we finally have screens that can compete with a late 70s 4014 or 4016's 4k resolution, crispness, precise image geometry, and even pixel size from corner to corner. That they worked isn't too amazing. Just how well they worked is what was amazing. I liked how you could turn them off on a Friday evening, and the picture was still there when you turned them on on Monday morning, as crisp as when it was drawn on Friday.He didn't show one critically important feature, and one that was an option later on. They could display a cross-hair cursor dynamically, without affecting the stored image. The terminals had a joystick to control that cursor. Near they end they provided an option to dynamically display a small low complexity chunk of image, refreshed from a small buffer. Again this did not affect the main stored image, but being dynamic it could be quickly altered. I think they also had an option to erase specific sections of the screen, but I never saw that in operation. Considering the flood basis for screen erasure, I have no idea how they added that feature.Those tube were damned expensive. Like small apartment expensive. It was an application for capital expenditure just to get the terminal serviced if the tube was wearing out, and they did wear out.

author: jfiresto
author_rank: Frequent Contributor
timestamp: December 11, 2024, 07:13:04 pm
content: I once owned a well worn, university surplus Tektronix 4010. It proved invaluable when a software company tried to convince me their 4010 emulation was accurate. They fixed their bug.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 11, 2024, 07:32:11 pm
content: I am with TimFox. I used those in the 70s and 80s. And they worked as well as taking a Polaroid photograph of one time events. And made taking those pictures for the permanent record far easier. But at least on the ones I had access to they were fiddly and temperamental. Getting all the biases set right for the sweep rate in use was tricky, particularly for a new user. I have a couple of them in my pile of old equipment. They were cheap because someone thought they were non-working, but a few minutes of knob twiddling brought the screen back to life.But all in all not nearly as good as a modern DSO. Those antique scopes sit on a shelf while I use things made in this century. They share a spot with the mechanical integrators of the 1930s to 1940s. Really clever. A marvel of implementation. But not something I actually want to use.

author: coppice
author_rank: Super Contributor
timestamp: December 11, 2024, 08:03:34 pm
content: Quote from: CatalinaWOW on December 11, 2024, 07:32:11 pmThe oscilloscope versions of storage tube were pretty good when new. but became quite fiddly with age. Tektronix achieved some very high bandwidth versions, but never really made them easy to use. Things like the HP 1741 and 1744 were really nice to use as a day to day scope for capturing one off or infrequent events in digital systems, with almost no fiddling around. When I had the first HP1741 in the company, everyone was finding reasons why they needed to borrow it.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 12, 2024, 12:53:29 am
content: Quote from: coppice on December 11, 2024, 08:03:34 pmI can't t argue with that. I never worked with one new out of the box. As a junior engineer in a lower priority department the scopes I got to use already had a couple of years on them. And obviously the ones on my shelf are very long in the tooth. Only used and own Tek scopes. The few HPs that came into the lab didn't trigger well in our application.

author: SteveThackery
author_rank: Super Contributor
timestamp: December 12, 2024, 06:18:31 pm
content: Quote from: CatalinaWOW on December 11, 2024, 07:32:11 pmI agree. The one I used back in the '80s was very fiddly to set up, and quite prone to "blooming" after several seconds, regardless of how carefully it was adjusted. However, the big message for me is how incredibly smart our forebears were - they did loads of ingenious things.

author: Analog Kid
author_rank: Super Contributor
timestamp: December 12, 2024, 06:53:16 pm
content: I used one of those Tek terminals back in college in the mid-80s when I took a FORTRAN class. (The assignment was just to draw some geometric shapes.) I thought the storage 'scope was pretty kewl, and I had no idea how it worked: I thought it might just be long-persistence phosphors or some such.

author: TimFox
author_rank: Super Contributor
timestamp: December 12, 2024, 07:19:35 pm
content: The important thing about storage CRTs is that the charge is "written" onto a dielectric coating over a conductive grid, which is "read out" by a beam through the grid that hits the phosphor screen visible to the user.Playing with the conductive grid under the coating controls writing, readout, and erasure.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: December 12, 2024, 09:50:48 pm
content: It's fun stuff, I had a HP 1741 and had to run a "deep erase" cycle when I first got to get rid of the last waveform written to it. But it was fiddly to get the storage to work, I ended up using it in conventional mode but it just got dimmer and dimmer.I wouldn't mind one of those huge Tek terminals however.

author: nfmax
author_rank: Super Contributor
timestamp: December 12, 2024, 10:13:27 pm
content: I remember using a Tek 4010 terminal with a PDP 11-33 as a third year undergraduate, then 4051 & 4052 computers as a postgrad. There was a thermal printer, that read out the tube image somehow and printed it on nasty paper. I’ve still got a couple of prints, which are even legible after all this time!

author: BrianHG
author_rank: Super Contributor
timestamp: December 13, 2024, 03:40:11 am
content: Quote from: Alex Eisenhut on December 12, 2024, 09:50:48 pmI gave away to my friend a Tek scope in the early 2000s. As it aged, the storage mode also got dimmer and dimmer.He got the service manual and tuned it up. I never seen the storage so bright or sharp.

author: jfiresto
author_rank: Frequent Contributor
timestamp: December 13, 2024, 11:20:05 am
content: Quote from: nfmax on December 12, 2024, 10:13:27 pmDid a mental fetch of the model number post-increment or pre-decrement a digit of a PDP-11/23 or PDP-11/34?

author: nfmax
author_rank: Super Contributor
timestamp: December 13, 2024, 12:18:50 pm
content: Quote from: jfiresto on December 13, 2024, 11:20:05 amI realised I had mistyped the number when I woke early at 5:30 this morning. 11/34 is what it was

author: chilternview
author_rank: Frequent Contributor
timestamp: December 13, 2024, 01:08:42 pm
content: I recall those screens on a Calma GDS1 we had at Fairchild back in the late 70's. The flash when erasing the whole screen gave you a headache after a while!