I recently got a bunch of old 80’s crts which I cant find any information about online.
I do have the service manual tho link
Looks like standart composite with external Horizontal and Vertical Sync to me but I’m not 100% sure and I dont want to fry anything
Thanks,
Oha
You must log in or # to comment.
I’m not sure exactly what you’re asking, and I probably don’t know the answer anyway, but I felt compelled to add a safety warning for anyone working with these.
The CRTs themselves can hold a high voltage for a long time, please be very very careful.
The service manual says they were made for an F55 video terminal. 1980s video terminals had video driver boards in them to convert the TTY signals to video. That driver board varied wildly on the output signals, some would output composite video leaving the monitor to control the raster scan, sync, horizontal & vertical sweeps but some would output all of that and there would be minimal circuits in the monitor cage. Hopefully you have ones that take composite video. can you get pictures of the back and sides?
Also, as others have said BE CAREFUL! the crt itself is actually a really big capacitor that can store a lot of potential and deliver a high voltage zap long after it is unplugged. While it’s running the fly back circuit produces 1KV (1000 volts) or more so I say again BE CAREFUL.
While I know(at least to some extend) what I’m doing, I still appreciate the warning. The Monitors.only interface seem to be these Pins labeled J1 in the Manual.
Heres a picture of the entire Board in case that helps:
(I know, that brown discoloration looks horrible but it still generates high voltage and makes that high pitched crt whine)A3.2 and B2.1 in the manual show you the pinouts of that jack and the expected signal, unfortunately section 6.1 schematics and sec D timing diagrams seem to be missing. You’re going to need to find a suitable driver circuit. Without looking at the timing it might accept input from an old MDA adaptor or similar.
https://en.wikipedia.org/wiki/IBM_Monochrome_Display_Adapter
Edit: While this in behind a paywall it looks like this old article has a circuit for composite to TTL monochrome that would be what is needed.
https://www.elektormagazine.com/magazine/elektor-198812/47485
This one is from the 1980s itself and there also seem to be a lot of TTL to composite circuits out there that use fairly modern (and a lot fewer) components so with a bit of looking you might find a modern composite to TTL driver circuit. Look at the retro computer and retro arcade game forums, etc.
Forgot to reply but I got another scan of the manual that includes these scans from the person that gave me the crts. https://i.ohaa.xyz/raw/oRiMLv.pdf
Thanks, I really appreciate your detailed answer.
Those look like CRT units without cases, which is slightly terrifying. Be careful.
What’s on the back of it (i.e. connectors) and what country are you in? (i.e. PAL, SECAM, NTSC)
Likely connectors are RF aerial, BNC, component, composite. Maybe s-video?
Assuming they still work and power on safely, you may find the issue is in generating a signal that they accept, with modern equipment. This depends a little on what you’re planning on using them for, and therefore what you want to connect them to.
Oh man, that manual is quite descriptive. I wish they could add a schematic or two there. But anyway, as others have suggested, be careful with CRT, but I guess you already know that. Next is from the circuit description, it seems like the display accepts some form or VGA signal without the color. You can see Ben Eater video to learn more about it, especially the line sync and vertical sync signal part
VGA might be a good idea. Do you think that these are just regular 640x480 displays? Can I damage them with a wrong resolution?
