Keohi HDTV - ISF - Mr Bob - Sequence of Tweaks

[ISF][MR BOB]

Sequence of Steps in Tweaking the TV

Here are general guidelines for the adjustments on the TV as offered by experienced video specialists/calibrators:

Tip from Mr Bob

"You always start with the mech. focus, because if your geometry/convergence is perfect and you have to redo your mech focus on any of the 3 guns, the g/c will be off on that gun afterwards.

You always do your geometry before your convergence, because some TVs have the green carry any geometry adj.'s with it. Some don't, and the green is independent of everything else. Since green is your template, it is important to set your template up first, then converge the red and blue to the green, each.

The precision blue electronic defocusing affects the grayscale, which should be done last. Electronic blue focus should be tightened up as much as possible for use during the convergence ops, then defocused very finely when doing the grayscale ops. You need to know how much electronic blue to defocus before you will know how much blue drive you actually will need to get D6500K. Since electronic blue defocussing mimics blue drive, that all has to be factored in together during grayscale setup.

Then you have to go back and retrim the blue convergence, in case it made any of the convergence go off by defocusing it electronically. Electronic blue defocusing can trigger astigmatism errors in the blue CRT, making perhaps one side go off more in one direction than another.

Tip from Tom Herman:

Normally the sequence for a full blown calibration is (or at least what I did)

adjust mechanical & electrical focus (because focus can affect gray scale).
adjust gray scale / color temp thru CUTs, DRVs, VR Screen controls (generally requires hiring specialist with a Philips analyzer).
adjust all mechanical & electrical geometries, & service convergence
all adjustments for Contrast, Brightness, Saturation, Sharpness, color decoder, etc.

Tip from Michael TLV: tip from michael

"Following a warm up period of 1 hour, set the TV to the "Warm/theater" mode and begin setting up the image using the Video Essentials/AVIA disc. Doing the brightness, then contrast, then colour, then tint, then sharpness. You've established your first baseline. This is as good as it gets via the user adjustable controls.
Now take a reading with the colour analyzer of the grayscale from 20 ire through 100 ire to chart out the precalibration grayscale tracking. Writing down all the numbers of course so that you can graph them later.
Enter the service mode of the TV and begin centering the image and reducing the overscan on all sides. Overscan is typically more than 5% from the factory. I like to shoot for something in the order of 1 to 2% where possible. On a RPTV, this will mess up your convergence a bit.
Time to see about removing the protective screen. You can do this pretty much at any time or not at all.
Do electronic focus next. Take off the front panel and access the 3 focus knobs / trimpots. You can either do the focus by turning each individual crt on or you can leave then all on and purposely misconverge the three colours so you can see each one distinctly. Now tighten the focus for the R/G/B. I've done the focus both ways and I think they are pretty much the same, although some would argue otherwise. There might be a theoretical advantage to doing the focus with all three crt's on at the same time. You want to get each of the guns to be as sharp as possible. The Red will be the tightest ... then the green, then the blue. Often, it will seem like the blue just doesn't want to focus very well, but resist the temptation to defocus the red and green to match the thickness of the blue. You will regret this if you do.
Do the mechanical focus now. If the individual CRT's have wingnuts, unscrew them and physically start turning the lens on each CRT. This is best done from the back of the set with someone in front giving directions. You will have to take the back panel off to do this though. Careful.
Convergence. Now tackle the convergence of the three CRT's via the service menu convergence adjustments.
Geometry. Use the various adjustment parameters to try and fix any geometry problems. Typical parameters to use are PARA - parabolic, TRAP- Trapezoid, VLIN - Vertical Linearity. A more extensive geometry adjustment will involve the use of convergence overlays or the string/ruler method. If you go this route, shut off the three crt's and then bring up the red first ... align. Then shut off the red. Bring up the green next ... align ... shut off. Bring up the Blue last ... align ... shut off. Bring up green ... and red ... align the red to the green. Shut off red. Bring up the green and blue ... align the blue to the green. shut off blue. Bring up all three crts and do any final tweaks to the alignment. Your set is now converged and geometry corrected.
Grayscale adjustments. Now it is time to set the proper grayscale with the colour analyzer. When completed, take a post calibration reading from 20 ire to 100 ire.
Go back to the VE/AVIA discs and do the brightness/contrast/colour/tint again setting up these in the service menu as your default positions.
Take another grayscale reading from 20 ire to 100 ire and make further small adjustments if needed. You may go back and forth a bit more here.
Disable SVM where possible and applicable.
Other tweaks ... include cleaning the mirror inside the TV. Cleaning the crt lenses.

That's it. This is pretty much the entire process that I have taken for my sets and those I have calibrated.

Some steps can be skipped at your discretion though. Each step when implemented gives you an incremental improvement in the image you see. Some steps give more of an improvement than others.

For me, the top three things are: Grayscale, Focus and convergence."