Morbius,
Thanks for the explanation of the function of the quarter-wave plates. From your description, it sounds like the symptom of mis-adjusted quarter-wave plates would be a loss of light from 1 or more d-ila devices and they shoud be adjusted for max light output? Is this correct? Is this a mechanical adjustment to the optical block? From the schematic, I do not see any adjustment points on the DD PWB Ass'y.
My intent is to learn how to adjust and measure every adjustable parameter for absolute maximum performance. I have already gone through the adjustment procedures as outlined in the Factory Service manual (Common Dc, A-D Converter Aperture, Sub-Bright/Sub-Contrast, P.C. Adj, etc). Taking the covers off of the projector does not scare me. If I scr%w it up, I accept that responsibility. I am NOT learning this to go into the calibration business.
The symptom I'm seeing/trying to correct is I'm seeing contrast ratios of only about 300:1. The limiting factor is the amount of available red. To get 6500K at the top end, I have to crank the green and blue way down with the result being less light output/lower contrast ratio. With GIN off, red is almost 40% less than green/blue. Since I do not have another projector to compare against, I do not know if this is typical. Therefore I would like to measure/confirm/adjust the quarter-wave plates.
If anyone could help me out, it would be appreciated. Please do not try to save me from myself. I have the factory service tool, DMM, Oscilloscope, Dilard, ColorFacts, half a brain (most of the time)

and time to learn.
While I appreciate what Cliff and William do, that is not me. With as much time as I spend with my projector, It can not be a black box. One of the main reasons I purchased the G15 was it's adjustability, and the knowledge on this forum. (besides the picture).
So if anyone would like to help, we can discuss it here or offline via e-mail.