Correct way to set up raster geometry?

Art a écrit/wrote/schreef le/on/op 17/10/2005 H. Ignaas ;

Absolutely, this is not easy do do correctly, even for a qualified service tech :-)

Also, be sure that the optioncodes (sticker on the picture tube) are correct! The are often altered by a discharge in the tube...

You need a test pattern generator to display the correct pattern as specified in the service manual. You probably won't get away with this repair without the correct manual. Than you need to adjust all of the settings in the correct order. The service manual will tell you which pattern to use and what order to use when performing all the adjustments. This will prevent some settings from affecting others when done step by step in the correct order. That's why the service menu is hidden from the general public. You made a simple but common mistake by not realizing that default setting meant EVERYTHING would be set to default, including all the geometry settings. Normally you set all the physical adjustments such as yoke position, purity rings and magnets, etc. to the best possible picture, then adjust all the service menu settings, so assuming you haven't moved any of the internal physical adjustments, you just need to follow the correct procedure now.

I've used a PC with video out to display a test pattern on TVs, it's not ideal but it's close enough to get it to a point that you can use a calibration DVD to finish it up. It's a major excercise in patience though.

"James Sweet" bravely wrote to "All" (18 Oct 05 03:58:39) --- on the heady topic of "Re: Correct way to set up raster geometry?"

JS> From: "James Sweet" JS> Subject: Re: Correct way to set up raster geometry? JS> Xref: core-easynews sci.electronics.repair:345565

JS> I've used a PC with video out to display a test pattern on TVs, it's JS> not ideal but it's close enough to get it to a point that you can use a JS> calibration DVD to finish it up. It's a major excercise in patience JS> though.

BTW, the Nemo dvd has nice test patterns.

A*s*i*m*o*v

... If you don't know what leever "A" does then you better leever "B"

JS> From: "James Sweet" JS> Subject: Re: Correct way to set up raster geometry? JS> Xref: core-easynews sci.electronics.repair:345565

JS> I've used a PC with video out to display a test pattern on TVs, it's JS> not ideal but it's close enough to get it to a point that you can use a JS> calibration DVD to finish it up. It's a major excercise in patience JS> though.

BTW, the Nemo dvd has nice test patterns.

A*s*i*m*o*v

... If you don't know what leever "A" does then you better leever "B"

If this is a newer set you need a pattern overlay that tapes to the screen. The gererator is built into the set. All adustments are done in the service mode. Which requires the service code being entered via the remote control. Once you have the overlay it's a piece of cake.

I have the correct service manual and have also been in contact with an acquaintance who works in the Philips tech department. The set requires a pattern generator, it cannot display its own pattern. The nature of the procedures for setting up the geometry mean that perfection is unattainable, and trying to follow the procedures in the service manual is not easy; although it shows an order (presumably the order in which to do the adjustments) it does not explain them well. It refers to three of them in almost the same way - as adjustments for straight vertical lines in the middle of the screen, when in fact they alter the geometry in a different way. The main problem is not my ability to set up geometry so much, but the problem of whereby I can get the left side perfect, but the right side remains wavy, and since each adjustment does both sides at the same time, you ruin one to get the other better, and in this case the right one seems to have a permanent geometry error in the lower right portion which is not correctable by the limited adjustments.

Others seem to think I am aiming for perfection which is unattainable with today's cheaply built, relatively poor quality goods. As an example, an untouched 34" set only a few years old was pointed out to me. It was suggested I study that screen as carefully as I am studying the one which I'm setting up, since I was reminded that nobody else would pay as much attention as I am at this point. Interestingly, although I've watched programmes on that set many times, I never noticed the relatively poor geometry (amongst other anomalies such as purity and convergence imperfections). The horizontal borders on widescreen images are not level, but are bowing slightly, and the line tilts to the right. As for EW distortions, it probably has them but the raster width is set high enough to hide them off-screen and since I haven't bothered to get a test pattern into it, no one can be sure how slight or expansive such distortions may be.

Some of the problem seems to be down to a VDR (varistor) on the CRT base (coupling dag coating to ground) which got cooked before I replaced the shorted-winding LOPTx. I hoped it had survived its roasting, but it's listed as a known cause of width distortion and altering raster size with brightness changes (which the set also has right now). Thing is, I can't find a supplier for the part yet. It's simply listed as 1mA/50V max 125V in the service manual...