After spending 300.00 dollars to have two power modules in my 12 year
old 32" Zenith Model SL3285BG, I bring it home to find that I now have
a colored bulls eye pattern on the screen.  Red in the middle circle,
green in the intermediate ring and blue in the outter circle.  The
sound and the picture clarity seems fine but nearly impossible to
watch.

What is wrong and how do I fix it?  I will not take it back to the
only shop in town.

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Request for Question Clarification by pinkfreud-ga on 08 Feb 2005 16:16 PST

Do you own any degaussing equipment? If so, you might try degaussing
the screen with the TV turned on.

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Clarification of Question by marcola-ga on 08 Feb 2005 21:09 PST

I do not own any degaussing equipment but I am pretty sure that I have
not placed any magnets on or near the unit although I cannot speak for
the repair shop that had is for 4 months.  The way the pattern is
displayed on the screen it looks like the RGB projectors (if there is
such a thing) is out of adjustment.

Well I would suggest some ?person? has discovered pretty patterns on
the screen with a magnet. Sometimes it happens accidentally with board
magnets etc. PF is likely to be correct with degaussing, but it
doesn?t need to be switched on -- just you can see then if it?s
working.

TVs have in-built degaussing (demagnetising) but it?s not powerful
enough to remove the effects caused by a strong magnet. If you don?t
have a degausser (as if) you *can* remove the magnetism with a
powerful magnet but don?t put it any closer to the screen than is
required -- an inch or two. By rotating the magnet and slowly moving
it towards the screen then drawing it away whilst still rotating, the
residual magnetism is removed. You may find it easier to mount a
magnet on a hand drill for rotation. Some experimentation will be
required but I have occasionally used the technique and achieved
perfect results.

If this does not remedy, you have a more serious fault which would
require internal adjustment. Either that or the ?shadowmask? has
buckled -- rare but not unknown.

Post a comment if you want more discussion.

Best

I take it that you were not overly enamoured of the repairer so you
are reluctant to ask them to make good the repair.

Could you clarify a couple of points. Is the ?bulls eye? more or less
in the centre of the screen? What size is the discoloration (known as
?misconvergence? or more likely ?purity? in your case)?

If it is central and quite big (several inches), bearing in mind the
age of the machine, it might just be that the scan coils have slipped.
Newer models are not adjustable but with older ones, the scan coil
(aka deflection) assembly can be moved back and forwards for initial
purity and convergence adjustment. If this be the case, there are a
couple of wing nuts on the scan coil assembly (mounted on the neck of
the tube) which the repairer might have slackened off in the course of
general set-up and neglected to re-tighten. Especially if the TV was
transported on its face (the safest way), the coils could have slipped
-- quite heavy. If it is of newer design without adjusters, the scan
assembly is still clamped onto the tube with a small ring band. This
is slackened to rotate the picture, but always the assembly should be
fully pushed up against the tube. Perhaps this was slackened off and
has slipped.

If you are reasonably hands-on, you could take the back off and see if
the wing-nuts (or the tightening band) are loose. Moving the coil
assembly back and forwards (or fully forward if no wing-nuts) you
should find the position of best purity. Don?t touch *anything* else,
especially the (usually brown) rings at the back of the assembly.
These are for finer adjustment and it takes a bit more experience to
set them properly. Trusting I don?t need to advise extensively on the
potentially lethal voltages, but when moving scan coils touch *only*
the plastic. There are lots of points on the coils (let alone anywhere
else) which can make one swear abominably. One does become immune (or
inured) to death by electrocution but it?s a very painful learning
curve.

If however it does not have adjustable coils (or loose band) and the
discoloration is small in area, then it is likely to have come in
contact with a magnet. It happens. Usually the effect is off-centre
and non-symmetrical and degaussing is the only recourse.

One other thing. Degaussing circuits do fail quite regularly because
the elements get hot -- heat being a killer of solder joints and
components. So there is a possibility that the screen has picked up a
bit of magnetism which the degaussing should normally take care of.

I?ll look again tomorrow night (GMT).

Best

The colored circles start at 8" in diameter in the center the a 16"
behind it and the 32" behind that one.  The entire screen is covered. 
Blue on the outside edges and corners, a green donut inside the Blue
and the bid Red 8" bulss eye smack in the middle!  It looks like a
really blurry bullseye.  The pixels are not blurry on the screen.  The
picture is clear ... the colors make it unbearable to watch...

Mmmmm, well that does indeed look like the deflection coils have
slipped. I tried to find a picture on the web but found nothing very
clear after 15 minutes. Do you want to have a look inside yourself? As
long as you don?t mind a slow response we could go about it step by
step. I?m on GMT (UK) and normally on-line from midnight to 3 or 4 in
the morning so depending on where you are we could maybe do a bunch of
messages reasonably fast if I keep looking. So I shall post this
immediately just in case you are on-line at the mo.

Best

I am travelling at the moment and will not return until the first of
the week.  I'll check back in with you and we can get into the back of
the set maybe Monday night!

Thanks

No probs. Unless untoward events, I?ll check on Monday night.

Best

... and Tuesday night :-)

Best

Still watching :-)

Best