A classic 14-inch monitor from the late 1980s. A true multi-sync monitor, the horizontal scan rate ranges from 15kHz up to 36kHz (officially 34kHz but 36kHz works fine). So you can run all of the Amiga's graphics modes, as well as the Atari ST's low and high resolution modes. And VGA too!
There's just two gotchas.
Problem 1: The monitor has two sync processing PCB modules. Taxan bought these in from some geezer. They aren't documented, no schematic was avaialble (until now!). And the capacitors on the modules are SMD. That means they WILL leak everywhere and corrode the modules away. Once the traces are gone, you won't be able to fix it without the schematic. The other capacitors in the monitor are through-hole and may be OK. But the SMD electrolytics on these modules will be leaking. Even if the monitor works fine! (for now)
Problem 2: The monitor can run in three modes: MDA, CGA/EGA, and analogue RGB. Of course you want to use analogue RGB. But the pinout when in analogue mode follows the ancient IBM PGA/PGC standard!
So why not make a custom cable?
When in analogue mode, the monitor expects R, G, B on pins 1, 2, 3. And composite sync at TTL-level on pin 4. Pins 6-9 are ground. Pin 5 controls the vertical picture size, leave it disconnected.
Fine for an Amiga. But some Atari ST models don't have composite sync output. And PCs always have separate H+V sync.
You could use a conversion circuit to convert separate H+V sync into composite sync. Or you could modify the monitor to accept separate H+V sync (and composite sync). That's what I'll tell you about here.
Taxan Multivision MV775 Service Manual (actually for similar model, nearly identical)
Taxan Multivision MV775 MA-A001A-W sync processor module schematic (reverse-engineered)
Taxan Multivision MV775 MA-B001A-W sync-on-green processor module (reverse-engineered)
The easiest modification converts the pinout to the old 9-pin VGA standard. You can still get adapters that go between 9-pin VGA and the common 15-pin VGA.
Composite sync is also accepted on the vertical sync input. Not the horizontal like some monitors do!
You need access to the monitor's input board. You may be able to solder it in-situ. Otherwise a lot of screws to remove to get rid of the shielded cage to extract the board.
This is the board which houses the leaky sync modules. So you'll want to get access anyway.
You need to install two jumper wires, one solder bridge, and cut three traces.
First stage, around the big switch:
Cut the two traces marked in red, at the exact positions shown! Make sure you get rid of any copper shavings.
Now install an insulated jumper wire. It goes from the leftmost of the three "B" contacts, to the rightmost of the three "A" contacts. Shown in yellow.
Then bridge the two pins circled in purple. The leftmost of the three "C" contacts and the rightmost of the three "D" contacts.
Next stage, move straight down to IC006. One trace to cut and one jumper wire to install here:
Cut the trace where marked with red. This is the trace highlighted with the dotted purple line. It connects to pins 9, 10 and 11 of IC006. Cut it anywhere along the purple line. Be careful not to cut the traces next to it!
Now install the jumper wire shown in yellow. It connects pin 8 to pin 9 of IC006. Pins 9, 10 and 11 are still connected together (you didn't cut that trace).
Modification is done!
The monitor now has the 9-pin VGA pinout when in analogue mode:
TTL modes (MDA/CGA/EGA) work exactly as before.
The only function you lose? The ability for the video card to adjust the vertical picture size. Only used by the extremely-rare IBM PGA/PGC card.
Label the monitor with the new pinout. Otherwise the poor sod who gets it after you're killed will tear their hair out.
Make the pinout the same as the Commodore 1084 / Philips CM8833 / Atari SC1435.
Do the 1-cut and 1-jumper modification around IC006 as above. But the switch area is different (and more complicated):
12 traces to cut, 8 jumper wires, 4 solder bridges. Cut traces are marked in red. Wires and bridges are purple, green, blue, yellow. Keep wires as short and direct as possible. Flat to the board. Otherwise picture quality will be worse.
The monitor now has the same pinout as a Commodore 1084 / Philips CM8833 / Atari SC1435:
TTL modes (MDA/CGA/EGA) work exactly as before.
Everyone knows this pinout. It should be the standard for everything.
