An HD owner submits: "The upper right corner is the one farthest from the
red gun itself, which points to the mechanical focus being off.
I had a problem with my green focus -- the middle gun -- being off, and
it affected my image the same way -- the middle and top third were correct, but
the graphics during the news, say, were off -- bloomy, too large in comparison to the
other colors, green surrounded the letters... "
Mr Bob offers a fix for the red-blooming
(in the corner) problem described above:
The Cantilever Technique is about double checking your work -- or the work of the
factory on an initial basis before doing anything -- and using that feedback to KNOW you
have your mechanical focus the best it can be.
The first thing you do is to get your crosshairs up there on the screen and separate
them in a diagonal fashion, blue down and to the left, red up and to the right -- or vice
versa, to all you "Au contraire" - ians -- green unmoved, at center as usual.
Work on one color at a time. Don't worry about picture brightness -- mechanical focus is
not affected by a brighter or darker picture, the way the electrostatic focus is.
Concentrate on the scan lines in the crosshairs, at the center of your screen. When the
screen is perfectly focussed mechanically, you can count 'em on the red and green, from
several feet away, as long as your astigmatism alignment is not off. Starting out, on a
fresh out of the box unit, it's not uncommon to not be able to see the scan lines at all,
on those same crosshairs. But you will afterwards...
Blue is more challenging. Look for the edges on the right and left, how each little
scan line has a bulge at the edge, where the scan line ends. This may be all you'll have,
to indicate exactness of focus, on blue. But it's better than nothing.
It's always best to have your electrostatic focus as tight as possible before doing
this protocol, but then I could say that about the mechanical also, vs. the electrostatic.
You may have to go back and forth between the mechanical and the electrostatic, until both
are optimised.
You do this mechanical focussing protocol once the screen has been unlatched from its
attachment to the rest of the TV, in whatever way they have it attached; and the easiest
way I have found is to pivot it -- cantilever it -- from where it hangs at the
top, tho you may have to pivot it from the bottom on some brands of RPTV. When the
screen can be drawn out half an inch from center and you haven't lost focus YET, but at
half an inch from center you begin to, and TOTALLY lose focus at one full inch, you're
halfway there.
You then do the opposite in the "in" direction -- that's where a dry towel or
paper towel roll or anything else that won't allow finger grease onto your screen, comes
in. Push inward on your viewscreen sandwich for half an inch in from center, towards the
mirror -- the screen's very flexible, being plastic, just don't overdo it -- and check
again. If it does the same thing in that opposite direction -- keeps perfect focus for
that same full half inch in from center towards the mirror, loses it badly at a full inch
in -- THEN you know you're perfectly centered in your throw distance from lens to screen,
ie. the mechanical barrel adjustments. You know then that you're perfectly centered; the
focus is not better when in the IN, or closer to mirror direction, than it is in the OUT,
or farther away from your mirror -- and thus from your lenses -- direction. Your throw
distance focus BALANCE is now perfectly centered. Mechanical focus doesn't get any better
than that, and when all 3 have been done to these perfectionistic tolerances and
standards, you'll find the picture is much crisper than it was before.
What you'll usually find is that your initial inspection will reveal that the factory
setting only got it close to being evenly centered from the factory, on at least 2 out of
your 3 lenses.
Notice I didn't say guns. Lenses, here -- the focus on the tube ITSELF is electrostatic
and an entirely different animal, and is a different discussion. For that discussion,
suffice it to say that red and green need to be in tightest focus possible
electrostatically, and blue needs special attention.
But mechanically, at the wingnuts or the tape that hold the lenses in locked position
in their barrel properly, all 3 lenses need to be just as tight as they can possibly be,
as far as mechanical focus goes.
You'll find, then, when you inspect the factory's work, that you may have perfect focus
in center, perfect focus half an inch in, but bad focus half an inch out. Or vice versa.
If so, you're close, but no cigar. Only when the in and the out are perfectly and
symmetrically equivalent to each other, can you trust that you have your mechanical focus
precisely correct.
Amazingly, I don't think I've ever worked on a Sony RPTV that needed any correction,
that didn't pass this test with flying colors, out of the box. But Mit and Toshiba --
Lord, give me strength...
BE SURE TO MARK CAREFULLY, WITH THIN LINES, EXACTLY WHERE YOU
START THE MOVING, IE, WHERE THE FACTORY SETTINGS ARE, ON YOUR LENS BARRELS. You'll
need to know exactly WHICH direction to go with each of your corrections, to wind up where
you want to be in the end. Go in 1/16" increments max, smaller once you're closer,
till you're there -- till everything is equalized, in to out. Be VERY observant as to
which direction does what.
I have found that if your focus starts to go into proper focus as you're pulling your
screen OUTWARD, you have to come OUT with the barrel -- usually meaning UNtwisting the
barrel -- to compensate accurately. If the focus starts to get better and winds up perfect
and crisp while you're pushing IN with the paper towel roll or plush towel, your barrel
needs to go IN towards the CRT face to compensate, usually meaning a screwing, tightening
direction. That may be the opposite on your RPTV, it may mean turning the barrel to the
right or to the left, you'll have to observe the slant of the notch the wingnut or guide
is placed in, to know for sure. Good luck, and happy screwing. Uh, let me rephrase
that -- happy UNscrewing. No, that's not it either...
