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DECpc 433 Workstation Video Issue

R

RadRacer203

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Sep 25, 2016
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Location
Burlington VT
Just picked up a DECpc 433 Workstation today and it works like brand new apart from one thing. The vga out is completely saturated in green. I know it's not my monitor because I've been using it fine with several other computers. The rotary dial at the back does change the video some but not the colors. I don't have the manual for ot and it's pretty weird for a 486 so I'm not sure what I should do.
 
If that's the same unit I had many years ago, and it appears to be, it displays basic vga w/64khz timing. Meaning a normal 31.5khz vga monitor won't work. It was intended for a large fixed frequency workstation monitor, sony gdm-1950 or equivalent, and also the 16" variety. There may be drivers for additional modes, as it was driven by a TI TIGA 34010 or close. I never obtained any drivers.

A guy in Mass was selling these w/o cpus or ram iirc Around 1995. I obtained a Cyrix 486-66 and was good to.go. Still have it but not the DEC pizza box. Groovy as all hell, I loved it as I had piles of fixed freq crts in those days.
 
DECtechGuy said:
These may help if you don't have them already:

Service Manual:
https://drive.google.com/file/d/1OInOw6W9-LNtsReF9AJ6q2RZTRCDT01R/view?usp=sharing

Technical Reference:
https://drive.google.com/file/d/1VLkqDN93NAJPKvd254Ibvy6tTjrVOpRr/view?usp=sharing
Click to expand...

Thanks, I was looking for those but couldn't dig them up on google.

Maybe the different scan rate is causing the issue with the green tint? I get a perfect, albeit off centered picture on a little LCD I have for testing
 
The wrong scan rate is what I'd be looking at. I can recall finding out which settings on that rotary dial did what, but I don't have the source of that anymore evidently, despite me hoarding any DEC manuals I find on the internet.

I think either 11 or 12 were a normal 60hz? The green hue almost reminds me of Sync-on-Green issues, but the pin-out on table 10-3 clearly shows composite sync, so it's not that.
 
Some monitors can be finicky so it could be difficult to determine what the problem could be. I had a bog standard 19" 48khz Sony that worked fine with my Mac IIx (with appropriate video card obviously), but wouldn't sync up on a friend's powermac. It's unlikely the problem, but try a different cable for starters. Or a different monitor.
 
tipc said:
Some monitors can be finicky so it could be difficult to determine what the problem could be. I had a bog standard 19" 48khz Sony that worked fine with my Mac IIx (with appropriate video card obviously), but wouldn't sync up on a friend's powermac. It's unlikely the problem, but try a different cable for starters. Or a different monitor.
Click to expand...

I'm betting it's probably just the monitor. Works fine with an LCD I have. I want to try it with a few others to be sure but I only have the one CRT and LCD handy at the moment, as far as vga stuff goes
 
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