The optical focus involves moving the lens so it is optimally focused.
Electronic focus involves turning a potentiometer just inside the front ofthe set so the electronic beam inside the CRT is optimally focused (though often blue is deliberately defocused slightly).
There's no focus I know involving moving the CRT itself.
Keep in mind there are lethal high voltages on the CRT.
If you're talking about optical focus, you have to remove the projection screen (above the area you're working on) to get to the setscrew that holds the lens. However, all the recent Hitachis I've seen have been properly focus optically. If you do this, be careful not to overtighten the setscrew when done.
Yes, I did the electronic focus using the little dials...
Now I'ld like to do the mechanical focus on the lenses... any additional suggestions on this?
Also.. in regards to the CRT.. I thought there would be 3 CRTs, one for red, green, and blue.. is this not the case? And, when focusing the lenses.. wouldn't I be fiddling pretty close to the CRTs ?
The lenses are typically in a separate cavity above the CRT's, so you don't get close to the CRT's at all.
Honestly, I'd suggest leaving optical focus alone because you're likely to be fine from the factory - unless you see some problem that needs correcting.
What is the "Sky Blue" adjustment?
I wonder if you can adjust for beam spot astigmatism by rotating the magnets on the yokes of the crt's.
A lot to play with if you know what you are doing.
But extremely dangerous if you don't know what you're doing. Dangerous to you and the set.
Don't touch Sky Blue - that erases all setting and reinitializes the set. In short - you're hosed.
Don't mix up the focus with the color level. Focus is on the bottom. You might want to tape over the color level pots so you don't mix them up.
THOSE YOLK CONTROL THE PITCH AND THE LEVEL OF THE SCREEN TOO..
THEY HAVE A WHITE PAINT LIKE COATING THAT WILL BREAK OFF IF REMOVED, ADJUSTED OR TOUCHED AND WILL SQUEAL ON YOU AND YOUR TWEAKING- THUS VOIDING YOUR WARRANTY.
I AM A TWEAKER, BUT THOSE SCARE ME.
I LEAVE THE MAGNETIC YOLKS ALONE SINCE, IF IT AIN'T BROKE I DON'T WANT TO FIX IT.
Anyone know where the fixing screw is on the guns ? I'ld like to do a manual focus...
see attached photo. [/QUOTE They actually say on the side which 3 are which in print. The focus is the bottom 3 on mine, one for each color gun. Maybe I am missing the question because your question is for one, and there are 3, and quite in view right when you open it up.
Focus can also be done from the front without completely removing the screen, you can raise the screen up 6 inches. This is better if you are alone doing focus.
From the rear, I recommend someone at the front helping to confirm focus.
Electrical focus is done by removing the front panel. Be sure not to touch the SCREEN VRs...only FOCUS.
If you have to ask, you shouldn't be doing it! Don't come back on anyone who suggested advice and say your set is screwed up.
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|Originally posted by frenchmarky
make sure to mark all those pots with a colored pen or paint pen so you can always go back to the original setting even if you screw up.
The good news is, your grayscale wasn't accurate to begin with. If you screwed with them, it is a good excuse to get your grayscale professionally calibrated.
|What is the reason you are saying you can't go back?|
this post will really disturb trhat last guy.......
...just pretend you didn't touch it. Since grayscale isn't accurate out of the box anyways, you are alright as long as you don't notice a glaring error in your grayscale.
I have the Hitachi service manual and it actually instructs technitions to calibrate it to 10,000K. Unbelievable!!!
Then adjust the cuts and drives afterwards to perfect it.
Takes some experience to get it right without equiptment though...
Most people who have the skill to eyeball it and do a good job usually don't mess it up in the first place...
And people who don't have the experience.... thier tv turns out green or pruple....
Greyscale really should be perfected by and ISF guy with equiptment.
|Originally posted by frenchmarky
Golly gee, I was just askin', common practice on tvs and such to mark pots before adjusting them, didn't know these were that goldarn sensitive. If you accurately mark a pot with a sharp, precise marking and put in exactly the same place it should have the same value as before unless it is a real cheap crappy pot, or it's dirty, or unless the pot has some huge range on it which these usually don't....apparently you are as touchy as these pots are....Frenchy
|Originally posted by Marc Alexander
The method Mike posted above is probably better than what Hitachi specifies.