Trident 8900c displaying B/W on a CRT monitor

[carlos12]

I recently bought an LG Studioworks 552V 14 ' CRT monitor. I wanted an IBM one but it wasn't easy for me to find one, but this works great and it was incredibly cheap (5€ + delivery expenses).

The problem is that while my OAK OTI card works perfectly, my other VGA card, a Trident 8900C, mistakes the monitor as a B/W one instead on a color one. So text and CGA modes display on gray scales. Curiously, the MCGA and VGA modes display on color. Also, the BIOS function to return the type of adapter returns the code corresponding to VGA on a mono monitor. This card has no problem at all when used with any of my modern flat screens.

Did something like this happen to anyone else? Thanks!

 

[Eudimorphodon]

Pins 4, 11, and 12 are the monitor ID pins on the classic VGA connector; the meanings of these pins were redefined in the mid-1990's, and the usual suspect here is pin 12. In the old standard pin 12 being grounded meant "mono monitor"; on newer monitors this pin a bidirectional I2C line used to transmit the DDC (Display Data Channel) information between the monitor and the computer. Because the state of this pin is "dynamic" it's possible for older VGA cards to get confused by it. It's essentially going to look like it's floating somewhere between ground and not, and because of "analog reasons" how this gets resolved can vary from card to card and monitor to monitor.

Pulling pin 12 out the monitor connector would fix it, but it of course would mess up DDC support. If it has a removable cable you could just modify a cable to eliminate the problem.