Introduction

Guy Kuo was kind enough to post his excellent G2 procedure on the AVS Forum, which KennyG subsequently edited. You can see this orginal post here.

I tried this procedure after I retubed my XG1350, and it was a great improvement, however it wasn't quite right. I found that after using this procedure, I had the problem that the rasters were lighting up too early, so if I set my brightness controls using Video Essentials or AVIA, the rasters were already well alight. This meant that blacks were no longer black, but dark grey, and that black detail was being crushed.

After a bit of experimentation, I realised that the use of the AVIA "Crossed Vertical Ramps" pattern as suggested by Guy was in my case, subjective, and not repeatable. In fact, I had a friend help me with the G2's one day, and we both kept coming up with different figures while looking at exactly the same pattern! This led me to do a bit of research into the subject, and I came up with the modified procedure below.

The basic procedure outlined below is very similar to that posted by Guy, except that it uses a different pattern from the Video Essentials DVD. The Advanced procedure which follows that allows the user to fine tune the procedure to extract better black level performance.

If you want to understand what each of the sub brightness controls does, look here.

Shortcuts

• The passcode to enter service mode is 3151
• You can reset any setting back to its default value by hitting CTL+NORMAL, then Down Arrow, then Enter, then Enter again.
• You can cycle quickly between the sub-brightness adjustments (Drive Control, Bright Gain, Bright Bias and Black Bias) by hitting CTL+KELVIN keys on the service remote.

The Basic Procedure

1) Warm up the projector for at least 30 mins before starting the procedure

2) Set your HTPC or scaler to the highest resolution that you use

3) Set your HTPC or scaler brightness and contrast levels to the defaults

4) Turn the "Blue Focus Tracking" off, then display the focus pattern, and adjust the blue focus pot for the sharpest focus, and then tun the "Blue Focus Tracking" back on. This ensures the correct amount of blue defocusing.

5) Set all of the Kelvin adjustments to 50, both Black and White.

6) Open the Blacking to maximum in all directions

7) Set the brightness to 60, and the contrast to 75. These are the default settings

8) Set the "AKB" test switch the "Test" position

9) Using a DMM, measure the voltages at test points TP7404 (Red G2), TP7504 (Green G2) and TP7604 (Blue G2). They should all be 2.5V +/- 0.1V. If they aren't, then try small adjustments to the Contrast control, and see if that helps. If not, then give up and call in a service technician.

10) Set the "AKB" test switch back to the "Normal" position

11) Adjust the Black Bias, Bright Bias and Bright Gain to 50 (the default) for all colors as a starting point

13) Use the Video Essentials DVD, and go to Title 15, Chapter 15, time 2:15, where you will find a crossed stepped IRE pattern. Pause the player here.

14) Begin the "Sub Brightness" Loop for each color, first Green, then Red, then Blue

14a) Begin the "Bias" Loop

Look into the lens and Adjust the "Bright Bias" until the rasters just dissapear

Adjust the "Black Bias" so that the voltage at the correct test point (TP7404 for Red, TP7504 for Green and TP7604 for Blue) is 2.5V +/- 0.1V

Repeat the bias loop until no further adjustments are made

14b) Set the brightness down to 0

14c) Look into the lens and adjust the "Bright Gain" until the 30IRE bar just dissappears. NOTE: The bar in the centre of the pattern that goes through both upper and lower step patterns is the 50IRE bar. The 30IRE bar is two away from that.

14d) Reset brightness back to 60

14d) Repeat the "Sub Brightness" loop, including the "Bias" loop, until no further adjustments are made

15) Start the "Sub Brightness" loop for each color

16) You now need to recalibrate the greyscale

17) Readjust Brightness, Contrast and Kelvin for each of your input memories

Make sure that when you increase the brightness control, that the rasters for each tube light up at the same time. If they don't, go back to the "Bias Loop", and make small adjustments to each tube until they do

The Bright Gain control is the source of a compromise on the XG's that we could really do without. If Bright Gain is set too low, then the rasters will light up then the brightness has been calibrated correctly using Video Essentials or AVIA, causing Blacks to become Dark Grey instead. On the other hand, if Bright Gain is set too high, then the Gamma curve is compromised, resulting in a picture where the bright scenes have plenty of punch, but the dim scenes are too dark and dull. If you find that either of these symptoms describes what you are seeing, try using the 20IRE or 40IRE bars as the reference for the Bright Gain adjustment above and see if you can achieve a better compromise.

Contact

If you have any questions or even better, suggestions for this procedure, please feel free to email me.