this post was submitted on 10 Aug 2025
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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

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[–] AbidingOhmsLaw@lemmy.ml 3 points 2 months ago* (last edited 2 months ago) (1 children)

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.

[–] Oha@lemmy.ohaa.xyz 3 points 2 months ago* (last edited 2 months ago) (1 children)

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)

[–] AbidingOhmsLaw@lemmy.ml 2 points 2 months ago* (last edited 2 months ago) (1 children)

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.

[–] Oha@lemmy.ohaa.xyz 1 points 2 months ago

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.