Small diameter CRT tube (15/8" ~ 41.3mm) screen type VLS492G or CV1527 - Page 1
Forum section: electronics / general

author: peteb2
author_rank: Regular Contributor
timestamp: November 03, 2017, 06:19:00 am
content: I have gotta ask, would anyone have the slightest knowledge as to what equipment such a small CRT screen may have been used? More than likely military equipment during WWII or perhaps the Cold War era i guess but it just seems truly a mystery to myself and friends. Google searches reveal the device in museum collections and that's all. I have a couple of them in their original sealed up boxes and i am wondering what i might do with them apart from just leave them in their boxes.... !Some have shown me the fashion of making a CRT become an analog clock display. Perhaps that would make an interesting project but at 15/8" diamenter screen it would would need a magnifier to see it i guess!The devices were made in the 50s (1954) by STC going from the datasheet:http://www.mif.pg.gda.pl/homepages/frank/sheets/144/c/C6SS-1B.pdf

author: Ian.M
author_rank: Super Contributor
timestamp: November 03, 2017, 07:49:55 am
content: This is pure speculation, but a tube of that size would have been useful for data overlay via a prism or semi-silvered mirror in an optical sight system. It predates digital gun computers but as its an electrostatic deflection tube, its capable of being used as a vector display and could have been driven by an analog computer e.g. to overlay range information. Later on similar size and even smaller tubes were commonly used for electronic viewfinders on video camera systems.What to do with it? Well whatever you do will need filament power, an EHT supply, X and Y deflection amplifiers and probably a grid driver for intensity or just for beam blanking. Build them and see what inspiration strikes.

author: peteb2
author_rank: Regular Contributor
timestamp: November 03, 2017, 05:35:41 pm
content: Thank you Ian.M. I had thought something like that, a range-finder etc and 'portable' perhaps because of the 2V filament....My main work i repair TV cameras used by News Networks and the viewfinder is a monochrome very high resolution often bonded yoke-coil raster scanned 1.5" 16:9 tube. Back a few decades i had to go through early consumer camcorders and they'd use a monochrome CRT picture tube too with less than 1/2 " diagonal phosphor target!On the broadcast professional units i seen the associated circuits to drive the tube to have grown smaller and smaller and there remains a teen tiny LOPTI and a thickly silicon-insulation coated cable for EHT that connects to the tube side. These units are now virtually impossible to repair and buying entire viewfinder replacements are the go but the warning is they will soon all have to be colored LCD (or OLED) which many older shooters hate the thought of having to use!I'll start hunting down ways to make the sorts of supply voltages for the VLS492 and as you say go from there....

author: chris_leyson
author_rank: Super Contributor
timestamp: November 03, 2017, 05:46:52 pm
content: Can't say that I've ever seen these sort of CRTs in any comercial equipment apart from small scopes or maybe the odd spectrum analyser and then they were usually designed by radio amateurs or hobbyists. There might have been some Heathkit stuff out there that used small CRTs. Viewfinder CRTs would have been magnetic focus and deflection as you can get a much smaller spot size than with electrostatic tubes.

author: Cyberdragon
author_rank: Super Contributor
timestamp: November 04, 2017, 01:55:03 am
content: Sometimes they could even be used as tuning/alignment indicators on radio equipment.

author: peteb2
author_rank: Regular Contributor
timestamp: November 04, 2017, 08:07:14 am
content: Quote from: Cyberdragon on November 04, 2017, 01:55:03 amYou might be thinking of the "Magic Eye" which is a very different kind of "CRT" compared to the VLS492 that i am trying to discover what they might have been used in. On a Cats Eye (another name), the phosphor is not directly coating the inside of the tube's flat-end glass but deposited onto an internal metal structure and there is a cap in the centre to cover the bright glow of the heater.

author: Cyberdragon
author_rank: Super Contributor
timestamp: November 11, 2017, 02:42:45 pm
content: No, in military equipment they sometimes had full CRTs as tuning indicators. You would have line or a dot that you would align to a gratecule to tune it. Way more precise than a magic eye. I've seen them in person, but I can't find any pictures of them. If you've ever seen a McIntosh reciever, it's the same thing except tube driven.They were also used in the German Pathfinder aircraft equipment