True retro computing means to be /still/ solving those yesterday's problems, right? (-:
I know how old this thread is. William, not sure if you're still around, but if in like 10 years or so, someone crawls this group for his "green tint" problem on a "GXT", just like I did a few days ago, there might be a solution:

Some IBM graphic adapters seem to be outputting multiple sync signals at the same time.
For a GXT500, this seems to be
- Classical "Separate Sync" on the Horizontal and Vertical Sync lines (VGA pins 13 and 14)
- "Sync On Green" (SOG), a Composite Sync signal overlaid to the green analog signal.

How this is percepted depends on your 13W3 cable and probably flat monitor.
At least for mine, a Philips 190X6, I can say:
If Separate Sync is detected, the SOG will be ignored, and the green analog signal is taken for granted. It still has the overlaid Composite Sync signal in it, which results in a slight offset of the average analog voltage, so the screen becomes green.

My solution was to build a very short VGA male to female adapter, which sits between the 13W3 cable and a regular VGA extension cable.
GXT -> 13W3 cable -> Adapter -> VGA extension cable -> Monitor

This adapter breaks the Horizontal and Vertical Sync signals, and only conducts the true analog VGA pins
1 - RED
2 - GREEN
3 - BLUE
6 - RED GND
7 - GREEN GND
8 - BLUE GND
10 - SYNC GND.

This seems to force the monitor to check the GREEN signal for a SOG, and if it is recognized, it will be subtracted from the overall analog signal, removing that greenish fog.

Hope it helps.

On Wednesday, January 5, 2022 at 11:45:55 PM UTC-7, Christian Holzapfel wrote:
> True retro computing means to be /still/ solving those yesterday's problems, right? (-:
> I know how old this thread is. William, not sure if you're still around, but if in like 10 years or so, someone crawls this group for his "green tint" problem on a "GXT", just like I did a few days ago, there might be a solution:
>
> Some IBM graphic adapters seem to be outputting multiple sync signals at the same time.
> For a GXT500, this seems to be
> - Classical "Separate Sync" on the Horizontal and Vertical Sync lines (VGA pins 13 and 14)
> - "Sync On Green" (SOG), a Composite Sync signal overlaid to the green analog signal.
>
> How this is percepted depends on your 13W3 cable and probably flat monitor.
> At least for mine, a Philips 190X6, I can say:
> If Separate Sync is detected, the SOG will be ignored, and the green analog signal is taken for granted. It still has the overlaid Composite Sync signal in it, which results in a slight offset of the average analog voltage, so the screen becomes green.
>
> My solution was to build a very short VGA male to female adapter, which sits between the 13W3 cable and a regular VGA extension cable.
> GXT -> 13W3 cable -> Adapter -> VGA extension cable -> Monitor
>
> This adapter breaks the Horizontal and Vertical Sync signals, and only conducts the true analog VGA pins
> 1 - RED
> 2 - GREEN
> 3 - BLUE
> 6 - RED GND
> 7 - GREEN GND
> 8 - BLUE GND
> 10 - SYNC GND.
>
> This seems to force the monitor to check the GREEN signal for a SOG, and if it is recognized, it will be subtracted from the overall analog signal, removing that greenish fog.
>
> Hope it helps.

Oh, he's around...