Murugan wrote on 2020-05-18, 08:21:

Is it possible that it would only work with an Olivetti PC??!!!

Perhaps the wiki entry would help explain this a bit: https://en.wikipedia.org/wiki/Olivetti_M24
This is for M24 but M240 seems to be mostly a 10MHz clock upgrade to the 8MHz 8086 in the M24. Which is already a pretty unique machine, there weren't many actual 8086-based ones.

Anyway, the M24 has a custom CGA-like graphics card and so perhaps the monitor is just RGBI and not true EGA. Also, it seems to use 50Hz VSYNC which again is a custom Olivetti thing and not even compatible with other CGAs.

I read that article but not 100% it seems.
It would explain the fact that none of my cards show something on-screen except some garbled lines on top.
Going to open the PC and take a look at the card.

Too bad almost no info is found about the monitor.

Thanks for the help!

Murugan wrote on 2020-05-18, 16:09:

Going to open the PC and take a look at the card.

Is it possible to remove the shroud on the video cable from the monitor? I remember the early ones were screwed together from two metal halves, not full plastic. If so, make some photos and/or compare the pinout to a generic CGA and EGA. Because typically with a bad vertical frequency you still get some picture but no V-lock so it's scrolling up/down the screen pretty fast. If you only get some garbage at the top of the screen that might suggest the monitor is not getting VSYNC signal at all - because it's not on a pin it's expecting it to be.

Going to take a look tomorrow but I believe it's 2 metal halves.
Should Checkit give some info on the video adapter?
On the Commodore PCIII, I see some changes in the garble,probably more text from the POST, but still garble/lines and not text, all squashed on the top of the screen.

The connector is full plastic sadly.
Checkit 2.1 reports EGA and I took a look at the back of the PC. I see DIP switches that are set for EGA and 2 RCA connectors...
Weird that my other cards give this garble...

Murugan wrote on 2020-05-19, 18:40:

The connector is full plastic sadly.
Checkit 2.1 reports EGA and I took a look at the back of the PC. I see DIP switches that are set for EGA and 2 RCA connectors...
Weird that my other cards give this garble...

Well, the sync signals are TTL so if you have a scope or a meter with frequency counter going up to 50kHz then you could probe the V/H pins (8 & 9) to see what's being output. I'm not sure how easy it is to detect EGA card, unlike VGA many registers on EGA are write-only. Could be a misdetecion, or it might indeed be an EGA but with different vertical refresh frequency.

TBH I don't have the more advanced tools for this hobby 😀 Only a simple multimeter, a soldering iron and an air gun.
Another EGA screen is coming one of these.... so then I'll be able to test some more.

M24 and M240 and M28 and M280 use propretary video timing. So original monitor only works with these machines.

The ATI EGA Wonder 800 card has a jumper that supports the 25kHz horizontal sync output mode required by these Olivetti monitors.

In the case of an M24 monitor, you'll also need to craft a DB9 to DB25 adapter.

See also http://www.vcfed.org/forum/showthread.php?652 … 9-adapter/page8