How to make a digital monitor analog capable?

[somebody@here.where]

Is there a way to modify a CGA monitor to accept an analog RGB
signal?  I have one such monitor, a Magnavox, that's gathering
dust and I would like to use it as a backup IIgs monitor.
Someone posted about bypassing some kind of chip on the monitor
and getting it to work with an analog signal.  This would be
great.  This particular monitor has CGA and composite video,
but no analog input.  Any ideas?  Schematics?

-Scott G.