I sort of figured it was monochrome TTL, but I haven't found pinouts online that match that. The closest IC to the display output is a PAL16C1CJ:
https://html.alldatasheet.com/html-pdf/126134/ETC1/PAL16C1CJ/98/1/PAL16C1CJ.htmlThe datasheet mostly just confused me more, but sort of confirmed that it is a digital, not analog output to me. Am I correct in this assumption?
I'd attach a picture but my phone died right after taking it.
Although I think the signals are digital, the CRT driver board seems like it's mostly analog. The only ICs on it are 555 timers. Does this info provide any clues?
I'm trying to work backwards from the CRT driver board to figure out what pins do what.
From what I've figured out so far, pins 3, 6, and 9 are connected to the ground plane.
Pins 2 and 5 lead to sections of the board with 555 timers. I'm guessing these are H-Sync and V-Sync. I didn't check continuity on this, since the traces go to the flyback transformer, which I haven't discharged, but on visual inspection it seems like these sections also go to the deflection coils. So it seems like my assumptions are correct.
What would the 555 timers do though?
Pin 8 leads to a trim pot labeled "video" so I'm guessing that pin is video. Could this be composite video, or based on the IC on the motherboard does it have to be TTL?
Does all of this seem correct?
If so, how might I adapt this for use with VGA, S-Video, or a composite signal? Could I generate the Sync timing with an arduino, or do the 555 chips do that?
And thanks a lot Kean, the links do help.
Edit: Since I wrote this, there was another reply which confirms what I found. Thank you duak, the pinout you provided is exactly the same as what I figured out.
Do you have a source for that image?
I'll see if I can get the main board powered on to see what the timing signals are. I stupidly took this board out of the terminal a long time ago though and lost the adapter that goes from the pin header to the D-Sub connector.
I think I can tell which pins are H-Sync, V-Sync and Video, but this might be a bit of a crapshoot.
Might there be a way to figure out what timing frequencies are needed with just the CRT board?
And yes, the brightness control is brought out onto a pot and does have high voltages across it. Thanks for the tip.