imac monitor adjustment: how to change factory settings?

[Andy Cuffe]

I just replaced the CRT in a rev B imac and have adjusted the grayscale
and geometry with the display adjustment utility 4.2. Everything seemed
to go fine, but I can't seem to change the factory defaults for the
geometry. Clicking on the 'Factory settings' button in the display
control panel restores it to the original factory settings, not the new
settings that match this CRT. The service manual gives no special
instructions on how to replace the factory settings. The new color
settings are fine, it's the geometry that won't save.