Anybody seen this Magic Focus screen disortion? - AVS Forum
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post #1 of 16 Old 09-04-2013, 08:28 AM - Thread Starter
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Hi all,
The TV itself is working fine.
I can adjust the convergence using magic focus manual mode
and it lines up quite well (geometry is good).

However, the auto mode is distorted,
don't know how else to describe it.
The boxes that flash up in the corners are no longer square,
almost as if it's gone out of alignment.

Anybody seen this problem?
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post #2 of 16 Old 09-04-2013, 10:09 AM
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Try your question here:

http://www.avsforum.com/t/695922/dont-dump-your-crt-rptv

"The wise understand by themselves; fools follow the reports of others"-Tibetan Proverb
 
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post #3 of 16 Old 09-04-2013, 12:02 PM
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Having those corner boxes non-symmetrical/non-square is typical of MF and totally normal.

That said, those of us who really value a great picture never use MF anyway. It only gets you close. Trust your instincts, Luke! Use manual MF, you can dial it in a lot closer/tighter with that than auto MF will ever do. You were on the right track already.


b

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post #4 of 16 Old 09-04-2013, 12:56 PM
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Best way to make sure is with a geometry pattern, easily found on any of the calibration discs available.

Usually, there are little circles in the corners for this exact purpose.

And, as Bob said, the auto version is vastly inferior to doing it manually. On my Hitachi, for example, the mirrors and wires for Magic Focus have been removed altogether.

But I'm nuts. Normal people just don't use it. ;)

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Did you really need to quote that entire post in your reply?
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post #5 of 16 Old 09-04-2013, 01:07 PM
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Not so nuts, Michael. Don't you have kids? Didn't you fear the day when they may have accidentally pushed it and wiped out all your hard-won manual convergence work? Isn't that actually why it's gone?

eek.gif

b

PS - The central big circle is just as important as any of the corners. You don't find that on HD pattern generators as it's too much of a resources hog and the algorithm would go on for years. Designers of such generators usually stay away from circles altogether. That's where Joe Kane's HD DVE is absolutely essential!

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post #6 of 16 Old 09-04-2013, 01:11 PM
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No kids, just nuts; guilty as charged.

I took out the eight mirrors to avoid any reflections. The wiring was just in the wrong place at the wrong time. ;)

Actually kept the stuff for a while, but finally threw it out last time I had the set open.


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post #7 of 16 Old 09-04-2013, 01:15 PM
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They are actually sensors, but they sure reflect like mirrors!

b

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post #8 of 16 Old 09-04-2013, 02:19 PM - Thread Starter
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Thanks Mr Bob and all.
The main reason I was concerned is - In the users manual there are a couple of diagrams (not photographs)
that show the screen and they look perfectly square. Here's what I'm referring to:
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post #9 of 16 Old 09-04-2013, 03:06 PM
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See what it looks like using something from one of the calibrations discs like this:

http://www2.tv-ark.org.uk/testcards/169.html


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post #10 of 16 Old 09-04-2013, 05:54 PM
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That sounds right, yes. But I have seen the MF in action dozens of times and it always has contorted corner boxes, just like your picture. Completely normal.

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post #11 of 16 Old 09-21-2013, 02:20 PM - Thread Starter
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Well seems as if the magic focus screen is the least of my problems.

Looks as if the TV has developed a fault.
When you first turn it on, there is intermittent flickering, horizontal lines and you can clearly see the convergence is affected.
For example, white lettering, the red will separate out by itself 1/2 inch or so, then jump back.

It does this on and off for about 2 minutes, then it behaves normally (with the picture as good as usual)
for as long as it's left on.

Seems like some component is starting to go. Convergence chips, which I hear so much about?
(I've seen the "repair kits" for this).
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post #12 of 16 Old 09-21-2013, 11:57 PM
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Could be cold solder joints on the legs of the ICs going to their boards. Or it could be internal cold solder joints inside the ICs.

I'd start by checking for that on the ICs, and if cold solder joints are found on the board, resolder them. If not found, replace the ICs.

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post #13 of 16 Old 09-22-2013, 05:11 AM - Thread Starter
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Thanks for the info. Can I ask a question - how much dis-assembly is required. Do you go in from the speaker grill area,
or from the back.

Well it got a lot worse, it's no longer useable. Whole thing is flashing, the bottom half is bowed and jumping about.
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post #14 of 16 Old 09-22-2013, 09:22 AM
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Your ICs need to be replaced. You always go in from the back on that repair. It happens a lot on CRT tech. It's no big thing, like a thermostat on a car that eventually goes out. You don't trash the car, you replace the thermostat. Those convergence ICs work very hard in there, and eventually many go out and need to be replaced. Nature of the beast. Always do all concerned even if only one color has gone out. The others will not be far behind. You will need to tighten up the convergence after the replacement, and retighten it up again after the first 100 hours of use, which we affectionately call the "drift period". Similar to the first 45 minutes every time you turn your set on. You have to allow it to thoroughly warm up to cruising temp before being able to really supertighten up the convergence. Eventually it will stabilize and go 100% correct on its own, after the first 45 minutes of warm-up.

I have not done this repair on a Hitachi recently, so will defer to others on these questions about the specifics of doing this replacement op. Just be sure to use generous amounts of heat sink compound on the new ICs, to conduct the massive heat they produce away from the ICs themselves to the heat sink fins, for convection cooling. And if there is build-up of dust on those fins, clear it off with a dry paint brush, so they can breathe naturally. I would leave the dust everywhere else alone in there, with the exception of the cooling heat sinks wherever they are in the circuitry. Cleaning things out runs the risk of jarring something loose and causing problems. Just stick with the heat sinks.

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post #15 of 16 Old 09-22-2013, 02:10 PM - Thread Starter
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Thanks Mr Bob.
Since i"m not the original owner, I don't know the history of the TV. I know the age is 9 or 10 years but
I've only had it for 3 or so years.

I'll look into it, I see the repair kit is available for $65. If I don't get any more feedback,
I'll update the board when I've done the repair.
regards,
Dave H.
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post #16 of 16 Old 09-22-2013, 02:51 PM
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I took my board out and sent it to Bob. Cost more, but it's still working. ;)

Michael


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