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NEC XG G2 Calibration

 

Back to Advanced Procedures Index

 

 



The following procedure was originally written by forum member KennyG. 

Several people have been asking about this, so here goes.

G2 is nothing more than the turn on/off voltage of your tube. If G2 is off, the only thing that will happen is Blacks and shadow detail will suffer because all the tubes are not turning on and off together... NEC XG's use a considerably more refined (or complicated?) procedure in setting G2/grayscale.

Color saturation can be left at your normal viewing adjustment.

Thank Doug Baisey, Guy Kuo, Jeff and all the other NEC guys, they gave this info to me, I simply numbered it and rewrote it slightly so it was easier for me to follow.

Steps:

1) Allow 30 min warm up.

2) Turn color saturation in your video processing all the way down, otherwise grayscale can be thrown off by several hundred degrees.

3) Set your processor to a minimum of line doubling, your can use anything above that also.

4) If your processor has brightness and contrast control set them to default.

5) Turn "Blue Focus Tracking" off...display focus pattern and adjust for sharpest focus, then turn "Blue Focus Tracking" back on. (This insures correct amount of projector defocusing) .

6) Set all "Kelvin" adjustments to default (50, both Black & White).

7) Open "Blanking" to max in all directions.

8) Set "Brightness" to 60.

9) Set "Contrast" to show 100ire window at normal level for your system (default?).

10) Set "AKB" test switch to test position.

11) Set your DMM (digital multimeter) to VDC and measure test points TP7404 (red G2) TP 7504 (green G2) and 7604 (blue G2) verify the voltage is 2.5 vdc +/-0.1 vdc...if not try small adjustments of "Contrast", if that doesn't help, call a service tech.

12) Adjust Black Bias to 50 (default) this is just a "rough setting".

13) Set "AKB" test switch back to Normal position.

14) Display AVIA "Verical Crossed Gray Ramp" pattern.

Note: Now begins the "adjustment loop" which you must repeat until G2 voltages no longer deviate from 2.5 vdc then readjusting and re-measuring during changes in the upcoming adjustments.

A) Begin Green Loop:

B) Adjust "Black Bias" to make TP7504 (GRN) read 2.5 vdc +/ 0.1vdc.

C) Look into the Green tube & see Gray ramps going vertically in opposite directions. Pay close attention to the dark edges of either ramp. Set "Bright Bias" to a point that just makes the dark outer edges of the ramps go black...the idea is to make the smallest amount of the ramp go black, make sure some of the ramp DOES go black.

D) Set "Brightness" to 0.

E) Look into the Green lens, you will now see a much darker looking ramp. Look at the edge of the ramp that goes from light to dark...Adjust "Bright Gain" to make the black edges of the ramps just meet at the center.

F) Set "Brightness" back to 60.

G) IF Green G2 still reads 2.5 vdc +/- 0.1 then exit Green adjustment loop...otherwise restart adjustment loop at step "B" (it's a good idea to run through this a second time anyway).

16) Begin Red adjustment loop, repeat steps B thru G.

17) Repeat steps B thru G for Blue gun.

18) From this point on, DO NOT adjust any of the Green gun's settings in the "White Ref" menu...this gun will serve as a reference by which Red & Blue guns are fine tuned for grayscale.

19) Calibrate grayscale using "Drive Control" for 100 ire window, and "Bright Bias" for the low end (30 ire) note that it will take several adjustment loops to get a flat grayscale, as these adjustment are dependent on each other.

20) Since you have probably had to change the G2 calibrated Red & Blue "Bright Bias" setting to get Red & Blue guns to track with the Green you must check your TP voltages again, if they are not at 2.5 vdc readjust "Black Bias" to get proper voltage.

21) Verify that "AKB" test switch makes only minor changes in screen appearance.

22) Readjust Brightness, Contrast & Kelvin for each memory slot.

Your done!

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