I've found a bunch of posts on here, and via Google, regarding this TV
and convergence problems. Most suggest that replacing the two STK392-
xxx ICs (110, 150, 180, 560 - mine are 560) and some fuses as the
solution.

That makes sense - the explanation is that the ICs go bad and take out
the fuses, resulting in no convergence. Fine. I can stomach that. But
my convergence is FINE when I turn the TV on, and flakes out shortly
after it heats up. Am I wrong in thinking that BLOWN ICs (and fuses!)
would cause a problem that would be consistently present from the
moment of power-on?

I'm not 100% sure of what happens to boards when CRT coolant gets on
them - but I do know that, at some point in this set's history, there
has been a leak. It appears that some got onto the board near the
leftmost (looking at it from the front of the set) convergence IC.

What am I looking for?

Addendum:

Only the RED "flakes out" - it works fine for a while, then jitters a
lot and goes WAY OFF. I just pulled the board and resoldered
EVERYTHING near the leftmost convergence IC, after cleaning that area
with rubbing alcohol. The problem remains.

I'm leaning toward a capacitor but haven't decided which one.

Cycling the power brings it back for a while...

The ICs could be bad, drifting as they heat up. But I don't blame you for
not wanting to perform what appears to be a shotgun repair.

wrote in message
...
I've found a bunch of posts on here, and via Google, regarding this TV
and convergence problems. Most suggest that replacing the two STK392-
xxx ICs (110, 150, 180, 560 - mine are 560) and some fuses as the
solution.

That makes sense - the explanation is that the ICs go bad and take out
the fuses, resulting in no convergence. Fine. I can stomach that. But
my convergence is FINE when I turn the TV on, and flakes out shortly
after it heats up. Am I wrong in thinking that BLOWN ICs (and fuses!)
would cause a problem that would be consistently present from the
moment of power-on?

I'm not 100% sure of what happens to boards when CRT coolant gets on
them - but I do know that, at some point in this set's history, there
has been a leak. It appears that some got onto the board near the
leftmost (looking at it from the front of the set) convergence IC.

What am I looking for?


You are either looking for a bad connection or you have a bad IC. Very
rarely you could have a problem in the convergence generator.

There is much information about these problems and repairing them in the
first ten posts he

http://www.hometheatershack.com/foru...html#post43725

Leonard

wrote in message
...
I've found a bunch of posts on here, and via Google, regarding this TV
and convergence problems. Most suggest that replacing the two STK392-
xxx ICs (110, 150, 180, 560 - mine are 560) and some fuses as the
solution.

That makes sense - the explanation is that the ICs go bad and take out
the fuses, resulting in no convergence. Fine. I can stomach that. But
my convergence is FINE when I turn the TV on, and flakes out shortly
after it heats up. Am I wrong in thinking that BLOWN ICs (and fuses!)
would cause a problem that would be consistently present from the
moment of power-on?

I'm not 100% sure of what happens to boards when CRT coolant gets on
them - but I do know that, at some point in this set's history, there
has been a leak. It appears that some got onto the board near the
leftmost (looking at it from the front of the set) convergence IC.

What am I looking for?

Well, they often do get bad solder connections at the IC's themselves,
caused by heating / cooling over the course of time, or one IC could be
opening up internally as it warms up.

We have done lots of these, and some were intermittent. If you get the
replacement IC's from a reliable supplier, you should be fine.


Mark Z.

On Dec 17, 2:03*pm, Meat Plow wrote:
On Wed, 17 Dec 2008 03:55:58 -0800, "William Sommerwerck"
wrote:

The ICs could be bad, drifting as they heat up. But I don't blame you for
not wanting to perform what appears to be a shotgun repair.

The convergence ICs are the hardest working parts in the set. It's
been my experience that when they go that's it. And depending on the
design they *blow fuses and/or smoke resistors.

I would rule out other problems before replacing these chips.

Based on what I've read so far, this set is of such a design that it
blows a set of 3.15A fuses that look like yellow resistors.

All such fuses are good.

After re-soldering the IC, it ran for about 5 minutes before it flaked
out again. I turned it off and back on, and it ran for another hour
without the major problems, until I got tired of watching it and put
it away for the night. I haven't tried it again today yet.

During that hour, it appeared that the red image was slightly larger
than the blue and green images - ie, it was converged at some point
nearish the middle of the screen (although, interestingly enough, not
the exact center), and there was red to the "outside" of everything. I
can't explain this too well, I guess, but "it looked like the red
image was bigger than the rest" should give a good idea.

I know nothing about the history of this TV, so multiple problems are
a possibility. After power-cycling, it ran fine for long enough that I
actually got tired of watching TV. My next guess, on the "total loss
of convergence" problem, is one of the four electrolytic capacitors in
front of the IC. They're cheap enough that I'm just going to replace
all four. I believe, however, that the "red image is bigger" issue is
a second, unrelated problem? Possibly even more mechanical than
electrical? I definitely need some guidance on this one.

I know nothing about the history of this TV, so multiple problems are
a possibility. After power-cycling, it ran fine for long enough that I
actually got tired of watching TV. My next guess, on the "total loss
of convergence" problem, is one of the four electrolytic capacitors in
front of the IC. They're cheap enough that I'm just going to replace
all four. I believe, however, that the "red image is bigger" issue is
a second, unrelated problem? Possibly even more mechanical than
electrical? I definitely need some guidance on this one.

Is the red image "smeared"? If so, check the electrolytic caps on video
drivers.