*Finally* got into the service mode of my TV (1 Viewer)

[Jim Peavy]

Been meaning to do this for quite some time, so I bit the bullet today and did it. Really not difficult at all; wish I'd done it a long time ago!

Anyway, for you seasoned pros, I have a question: I've identified the controls for blue drive, green drive, and blue cutoff, green cutoff, red cutoff. It appears they adjust the tints specified, but what's the difference between the "drive" controls and the "cutoff" controls?

Any info appreciated.

 

[Bob McElfresh]

Hi Jim. I'm going to move this thread over to the Display Devices fourm where some of the guys with this specalized knowledge hang out.

 

[Jim Peavy]

^ ^ ^
Thanks, Bob.

Okay, while I have you all's rapt attention, got another question concerning the squeeze mode on my TV (a humble Toshiba 32A42). It works quite nicely, but I notice on either side, starting at about 3 or 4 inches from the edge, the picture develops a sorta' "chicken wire" effect.

Imagine laying a screen with long diamond shaped openings over the image. As I said, the effect starts about 4" from the edge and gets worse the further from the center of the screen you go. It's not terrible, but is noticeable (depending on what's being displayed).

I realize with the squeeze trick I'm doing something that my (standard 4:3) TV is not exactly designed to do. But if'in there's something I can do about this slightly annoying effect, thought I'd give it a shot.

Any advice much appreciated.

 

[Chad B]

Hi Jim,

The drive controls are for bright whites, and the cuts are for darker grays. In practice, though, I've found that drive controls often have a fairly even effect over the entire brightness range, whereas cuts usually do effect the lower and mid brightness ranges the most. In other words, on a typical modern HDTV set, taking the green drive down by one notch might reduce the green at 100 IRE by 4%, 50 IRE by 4%, and 20 IRE by 3%. On the other hand, reducing the green cut might reduce the green by 6% at 20IRE, 3% at 50 IRE, and 1 or 2% at 100 IRE.
I'm not sure what would be causing the chicken wire effect. Do you have a test DVD? If so, did you try putting some test patterns up? I'd try a crosshatch pattern first and check for significant geometry, focus, or convergence problems.

Chad

 

[Jim Peavy]

Thanks much, Chad.


Yeah, I'll pop in Avia and look around some more. I thought this might be a common enough problem that someone might say, "oh yeah, of course - the ole' chicken wire syndrome...!".

Seeing as how my TV is a standard 4:3, is there any inherent reason it can't display a 16:9 image as well as it does a 4:3?

 

[ChrisWiggles]

I believe the Cuts are the G2 controls for each tube, the gains are the gains for each tube.

But I'm not super familiar with the silly labeling in consumer stuff, but that's my recollection.