You don't need to go to this bother - your monitor is picking up the separate sync just fine, so you only need to filter it out of the green channel. An L-C filter should handle it no problem, and on the plus side you don't even need to power it.
Or try to set the video mode and add the option '-sn', e.g.'/usr/gfx/setmon -sn 72HZ ':
Specifies the source of the sync signal. syncselect is any
combination of r, g, b, and a to represent the sync signal on the
same combination of the red, green, blue, and alpha video cables.
If syncselect is n, the sync signal will be generated on the sync
cable. If syncselect is not specified, the sync signal will default
to the green cable.
But a lot of setmon options work only on a couple of the 'bigger' graphics (RealityEngine etc)
_________________Now this is a deep dark secret, so everybody keep it quiet
It turns out that when reset, the WD33C93 defaults to a SCSI ID of 0, and it was simpler to leave it that way... -- Dave Olson, in comp.sys.sgi
Currently in commercial service:
In the museum
: almost every MIPS/IRIX system.Wanted
: GM1 board for Professional Series GT graphics (030-0076-003, 030-0076-004)