Philips 64PP9751 Grayscale Calibration Results-Thanks Gregg :)

Discussion in 'Archived Threads 2001-2004' started by Steve_V, Nov 18, 2001.

  1. Steve_V

    Steve_V Auditioning

    Joined:
    Nov 1, 2000
    Messages:
    2
    Likes Received:
    0
    Trophy Points:
    0
    Last week, I had the pleasure of receiving a visit from Gregg Loewen to calibrate the grayscale on my 9 month old 64PP9751. When I first received the set, the out of the box settings appeared reasonably accurate. This past April, the high voltage board failed resulting in the 9751 being out of commission for 30 days, after which, everything had a decidedly purple colorcast. It took an additional 3 service visits over a 2 weeks span for the Philips authorized tech to “eyeball” the grayscale settings to the point that the set was watchable.
    Anyway, Gregg arrived at approx 1:30, we chatted a bit and he got down to business which began with the VGA input on the Philips which I use with an HTPC. He checked and set overscan, horizontal and vertical size, and did mechanical and electronic focus along with a quick (but very effective) touchup of my geometry and convergence. Next, black level, white level, saturation and hue using AVIA. Since the Philips is acting like a computer monitor when in the VGA mode, most of the color controls are “locked” and have to be done by adjusting the video overlay settings on the HTPC—no big, just a bit more time consuming.
    With that done, Gregg checked grayscale using VE and his color analyzer. The pre-calibration readings were awful—a high of 24,100 at 50IRE and lows(??) of 15,000 at 100IRE and 15,100 at 20IRE. After approximately an hour of adjustments the post-calibration readings ranged from 6,680 to 6,380—EXCELLENT!
    As a side note, the authorized Philips service guy can’t be blamed for the horrendous settings. He actually followed the adjustment procedure published by Philips which involves setting up CRT Bias voltage using an o’scope and setting R, G, and B, cuts and drives “to obtain correct white balance” in the “light areas” and “dark areas of the picture”. Amazing :angry:
    Next, more of the same with my HD input—bump up overscan a bit, center the image, and another round of geometry/convergence touchup. This time test patterns were courtesy of Gregg’s (Sencore??) signal generator. After setting black level, white level, saturation and hue, etc, it was time to take grayscale readings. I don’t have the report from Gregg yet for this input, but from memory it was only slightly better than the VGA input readings. IRC that final readings were in the same range as the VGA readings, but don’t have exact numbers.
    Lastly, it was time for lens striping. Pre-striping readings ranged from 6,840, 6,440, and 5,600 for left, center, and right respectively. Post-lens striping readings 6,600, 6,500, and 6,400 for the same points.
    Overall, Gregg worked on the set for approx 5.5 hours and did an excellent job. The results are like night and day—I couldn’t be happier.
    Thanks Gregg!
    Steve
    [Edited last by Steve_V on November 18, 2001 at 10:15 AM]
     
  2. Steve_V

    Steve_V Auditioning

    Joined:
    Nov 1, 2000
    Messages:
    2
    Likes Received:
    0
    Trophy Points:
    0
    Hi Paul,

    Yup, just goes to show that no one should try to "eyeball" grayscale. I'm convinced the set was reasonably close when I first received it. Philips' field service procedure for setting grayscale is probably pretty typical of other manufacturers as well. Bottom line: if you've had a major part replaced you can be pretty certain color accuracy is shot.

    The difference since Gregg did his thing is stunning. Makes me wonder how I tolerated the pre-calibration mess.
     

Share This Page