I've got an intermittent problem on a 27" Sony TV
KV-27S36 where the picture "rolls up its eyballs"
and then goes blank: The bottom of the screen
goes blank first, and an up-shifted picture shows
at the top 1/4 or 1/3 of the screen, with scan lines
becoming coarser toward the bottom of this region
and then dark below. This situation twitches and
flickers for several seconds, then all goes dark.
Cycling power off and back on (after say 10 sec)
almost always restores the picture, sometimes
for hours.

The problem does not always arise on every
viewing session.

It does not seem to be particularly temperature
sensitive, in that spraying "duster" air-in-a-can (which
can come out quite cold!) on suspect areas seems to have
zero effect.

Poking parts with a stick also seems to have no effect
once the problem starts, but after the problem goes into
remission (after power cycling), poking at the HV cable
where it emerges from the flyback brings the problem back.

Assuming that there is something flaky about that connector,
I thought I'd just inspect and repair or replace it. But the
cable only wiggles up and down slightly, and I am uneasy
about giving it a serious yank. So, is this supposed to come out
with a yank, or is there some secret? What sort of connector
is down in the hole?

Many thanks for any help and advice!










Bob Masta

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!

This sounds more like a vertical deflection fault rather than a horizontal
fault. I have my doubts has anything to do with the flyback, unless it is
one of the supply voltages from that section.

Most of the common failures in your model series for this type of fault are
many of the electrolytic caps and cold solder connections to the output
devices since they run very hot.

Use a heat gun and circuit freeze to troubleshoot for the fault. Heat the
caps in the vertical deflection area, and then test them with an ESR meter.
You can then use the circuit freeze to test the questionable caps in the
cold state after you find them to be failing from heat.

--

JANA
_____


"Bob Masta" wrote in message
...
I've got an intermittent problem on a 27" Sony TV
KV-27S36 where the picture "rolls up its eyballs"
and then goes blank: The bottom of the screen
goes blank first, and an up-shifted picture shows
at the top 1/4 or 1/3 of the screen, with scan lines
becoming coarser toward the bottom of this region
and then dark below. This situation twitches and
flickers for several seconds, then all goes dark.
Cycling power off and back on (after say 10 sec)
almost always restores the picture, sometimes
for hours.

The problem does not always arise on every
viewing session.

It does not seem to be particularly temperature
sensitive, in that spraying "duster" air-in-a-can (which
can come out quite cold!) on suspect areas seems to have
zero effect.

Poking parts with a stick also seems to have no effect
once the problem starts, but after the problem goes into
remission (after power cycling), poking at the HV cable
where it emerges from the flyback brings the problem back.

Assuming that there is something flaky about that connector,
I thought I'd just inspect and repair or replace it. But the
cable only wiggles up and down slightly, and I am uneasy
about giving it a serious yank. So, is this supposed to come out
with a yank, or is there some secret? What sort of connector
is down in the hole?

Many thanks for any help and advice!










Bob Masta

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!

On Mon, 10 Sep 2007 12:23:13 -0400, Meat Plow
wrote:

On Mon, 10 Sep 2007 14:58:15 +0000, Bob Masta wrote:

I've got an intermittent problem on a 27" Sony TV
KV-27S36 where the picture "rolls up its eyballs"
and then goes blank: The bottom of the screen
goes blank first, and an up-shifted picture shows
at the top 1/4 or 1/3 of the screen, with scan lines
becoming coarser toward the bottom of this region
and then dark below. This situation twitches and
flickers for several seconds, then all goes dark.
Cycling power off and back on (after say 10 sec)
almost always restores the picture, sometimes
for hours.

The problem does not always arise on every
viewing session.

It does not seem to be particularly temperature
sensitive, in that spraying "duster" air-in-a-can (which
can come out quite cold!) on suspect areas seems to have
zero effect.

Poking parts with a stick also seems to have no effect
once the problem starts, but after the problem goes into
remission (after power cycling), poking at the HV cable
where it emerges from the flyback brings the problem back.

Assuming that there is something flaky about that connector,
I thought I'd just inspect and repair or replace it. But the
cable only wiggles up and down slightly, and I am uneasy
about giving it a serious yank. So, is this supposed to come out
with a yank, or is there some secret? What sort of connector
is down in the hole?

Many thanks for any help and advice!

Does it look like it's designed to come out? And what kind of repair do
you think you can perform upon it once it's removed? Unless the cable end
fits into a socket say like an auto distributor there might not be much
that can be done other than replacing the flyback.


Yes, it does look like it's designed to come out... looks exactly
like an auto distributor socket complete with rubber boot
that can slide up the cable. Since it seems to be quite
sensitive to motion, I assumed (hoped!) it was just a flaky
connection.

Best regards,


Bob Masta

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!

On Mon, 10 Sep 2007 14:07:35 -0400, "JANA"
wrote:

This sounds more like a vertical deflection fault rather than a horizontal
fault. I have my doubts has anything to do with the flyback, unless it is
one of the supply voltages from that section.

Most of the common failures in your model series for this type of fault are
many of the electrolytic caps and cold solder connections to the output
devices since they run very hot.

Use a heat gun and circuit freeze to troubleshoot for the fault. Heat the
caps in the vertical deflection area, and then test them with an ESR meter.
You can then use the circuit freeze to test the questionable caps in the
cold state after you find them to be failing from heat.


Thanks for the advice. I will certainly check into these things.
I agree the problem sounds like vertical deflection, but I am
trying to work with the fact that I can bring it on by gently poking
the HV cable at the top of the flyback. Doesn't seem to be
enough motion to be wiggling the whole flyback and thus
flexing the circuit board, etc.

Best regards,


Bob Masta

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!

On Tue, 11 Sep 2007 11:53:08 GMT, (Bob Masta)
wrote:



Yes, it does look like it's designed to come out... looks exactly
like an auto distributor socket complete with rubber boot
that can slide up the cable. Since it seems to be quite
sensitive to motion, I assumed (hoped!) it was just a flaky
connection.

Best regards,


Bob Masta

Some replacement flybacks require you to reuse the original HV cable.
On those flybacks, they cable has about 1/4" stripped which is
inserted in a one way gripper. Once it's in, there's often no way to
remove it without breaking it. While extracting it from the old
flyback, the stripped part of the wire often breaks off. The good
news is that since it doesn't pull out easily, it must be making good
contact with the gripper. If there was a bad connection there, you
would see the picture get bigger and dimmer then snap back to the way
it should be and you would hear arcing coming from the bad connection.

Have you re-soldered all the bad connections? Those sets often have
many bad solder connections all over the main board. Be sure to
re-solder the horizontal drive transformer (off the base of the HOT).
It often doesn't take much to make a bad solder connection act up.
The bad connection can be far from the part of the board which seems
most sensitive.
Andy Cuffe