Sony TV Color Went Psychadelic!


  #1  
Old 03-29-01, 10:36 AM
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I have a 20-inch Sony television that I purchased sometime in 1989 (yes, I know: be happy to have gotten so many years out of it and stop complaining! Still, complain I must).

When we turned it on the other day the colors were very wierd. Everything in the center is pink, followed by a green ring around that, and the corners are normal. The shape of this distortion is like a big football, or an eye, and the wierd thing is that it even affects the things like the volume indicator (the status bar across the bottom that used to be green, which is now blue/green/pink).

Well I read some stuff on this site and others about de-gaussing, and had even called a local repair shop and they mentioned the same possibility. I was thrilled to find out this might be a simple and inexpensive fix. But when I told my wife the good news, she informed me of an important element of the plot that had been missing: the TV got that way after she WHACKED it in frustration!

So now I think "Oh crap!", she probably caused permanent physical damage that would be just as expensive to fix as buying a new set.

Should I start TV shopping, or can this be repaired?
 
  #2  
Old 03-29-01, 01:51 PM
Smokey
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Good Evening, fubarSONY:

This doesn't sound too bad and the fix is easy. On the neck of the picture tube is a device called a deflection transformer....or more commonly called a "Yoke". This device is comprised of a plastic frame and has multitudes of wire in coils. It's purpose is two-fold. The yoke provides the magnetic field to deflect the electron beam in the picture tube to cause it to scan both vertically and horizontally. The second function is for "color purity". The position of the yoke on the neck of the picture tube determines that the electron beam strikes the phospher on the face of the picture tube at the correct point so that the tube will produce red, green, or blue as it should.

Once the yoke is positioned, it is clamped in place with a device much like a hose clamp on your car radiator hose. Sometimes the clamps are plastic. Over a period of years, the plastic hardens and gets brittle from the heat of the picture tube.

Take one irate wife who smacks the tar out of the television set, take an aging clamp on the yoke, and you have a clamp failure. The yoke slides out of place and now you have color purity failure. The picture may be cocked a little left or right.

You might get lucky and manage to move the yoke back into position and reclamp it. It has to be done with the set on so that you can see the colors reconverge to their natural state. As a technician, I have always adjusted the set controls (inside) so that the picture produces only a red screen (and, of course, the color is turned off). Red is the hardest color to manipulate in a television set and is the quickest to show flaws in color. So, you slide the yoke back up the neck of the picture tube and reclamp it in the spot where the picture produces a pure red screen.

Then, with the color off, you readjust the blue and green fields so that the set produces a good black and white picture.

Now, assuming you have no electronic expertise, take it to a shop and have the 50 cent clamp replaced and the purity reset. There are some dangerous voltages on that yoke (about 4000-6000 volts)and a push in the wrong spot can turn you into a crispy critter. I have the scars to prove it.

But, now you know what has happened and how it will be fixed.

Smokey
 
  #3  
Old 03-30-01, 09:30 AM
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Smokey,

Thanks for the fast and detailed reply. I just called a repair shop, however, and said "hey, I got some information online about what needs to be done to fix my TV." The conversation went like this:

ME: explained about the yoke, the clip, the picture tube.
TECH: What brand is it?
ME: Sony
TECH.: No, that's not your problem. Probably the de-gaussing circuit needs to be replaced. We do free estimates, so bring it in. If that's the problem, it would cost about $45 and be ready in a day.

Now, that sounds pretty fair to me, and I like that he was upfront about time and price. But I'm a little disturbed that you seemed so sure about this, and then he seemed so sure that that's not it!

Since the estimate is free, I have nothing to lose, so I will take it in this weekend and see what happens!
 
  #4  
Old 03-30-01, 10:55 AM
D
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Neither Smokey or the tech that you called has personally looked at this tv yet. Smokey has a lifetime of experience and a massive technical background, and 98 % of the time his advice can be taken seriously. However we are basing our advice based on the info provided and our experience and background. I would have been more interested if you told the tech I talking to my brother who is also a technician living on east coast and he suspects it is this... but advice me I would need it looked at, and then get your techs opinion on the fault based on how you describe it.

There is also no subsitute for having the unit in front of you to look at, things are not in all cases exactly how they seemed, but I think our team of DIY advisers do a pretty good job just the same but we are not gods.

If you can get a no obligation free estimate on the repairs then that is a good deal.
 
  #5  
Old 03-30-01, 02:26 PM
Smokey
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Thanks for the vote of confidence, Don. I have repaired more television sets than I care to recount and have seen a "slipped yoke" many times. Judging from the description I received, the circumstances that led up to it, etc., I feel confident that I am right.

Of course, if the person will take the back off the set and look inside, he can see the deflection yoke/transformer on the neck of the picture tube. It almost covers the neck of the picture tube. And he can tell if it is loose or solidly installed.

Some of the manufacturers through the years actually glued the yoke on the neck of the picture tube. If you replaced the picture tube, you had to replace the yoke at the same time. My experience was with RCA back when RCA was still a company (and not Thompson Electronics). In most cases, the glue deteriorated over the years from the heat of the tube and more problems developed.

There's a lot of history on TV repair. Mine began with the old black and white sets back in the early, early 60's. In 1964, we saw color come of age and I took all the courses and all the schooling to service the "new" era.

Smokey cares about your problems.
 
 

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