Emerson 19" TV Vertical roll on cold start

[Robert McPherson]

Model #: TC1972DA 1995 model year LA7837 vertical IC. Set works
perfectly when started cold, except for fast vertical roll. After
about 15 minutes of warm up, vertical syncs perfectly and stays OK
until set turned off. Freeze spray, hot air, etc around vertical
output circuit and Jungle IC (LA7676) have no effect. There is never a
heightproblem or a linearity problem. Have not been able to find any
bad capacitors in either area. Is this a known problem. If so, what
is the fix?

 

[Jerry G.]

Check for parts that have become thermo sensitive. Caps can especially
become thermo sensitive with age.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
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"Robert McPherson" <rm502@bellsouth.net> wrote in message
news:1fe013f5.0311191356.660044e@posting.google.com...
Model #: TC1972DA 1995 model year LA7837 vertical IC. Set works
perfectly when started cold, except for fast vertical roll. After
about 15 minutes of warm up, vertical syncs perfectly and stays OK
until set turned off. Freeze spray, hot air, etc around vertical
output circuit and Jungle IC (LA7676) have no effect. There is never a
heightproblem or a linearity problem. Have not been able to find any
bad capacitors in either area. Is this a known problem. If so, what
is the fix?

 

[David]

Capacitor problem in the video path circuit.
Since you say there is no problem with height or linearity likely is not in
the vertical circuit or vertical sweep generation circuit but in the sync
separator or video path before the sync separator.

David

Robert McPherson <rm502@bellsouth.net> wrote in message
news:1fe013f5.0311191356.660044e@posting.google.com...

Model #: TC1972DA 1995 model year LA7837 vertical IC. Set works
perfectly when started cold, except for fast vertical roll. After
about 15 minutes of warm up, vertical syncs perfectly and stays OK
until set turned off. Freeze spray, hot air, etc around vertical
output circuit and Jungle IC (LA7676) have no effect. There is never a
heightproblem or a linearity problem. Have not been able to find any
bad capacitors in either area. Is this a known problem. If so, what
is the fix?

 

[Creamed_emu]

David <dkuhajda@locl.net.spam> wrote in message
news:3fbc46d7@news.greennet.net...

Capacitor problem in the video path circuit.
Since you say there is no problem with height or linearity likely is not
in
the vertical circuit or vertical sweep generation circuit but in the sync
separator or video path before the sync separator.

David

Robert McPherson <rm502@bellsouth.net> wrote in message
news:1fe013f5.0311191356.660044e@posting.google.com...
Model #: TC1972DA 1995 model year LA7837 vertical IC. Set works
perfectly when started cold, except for fast vertical roll. After
about 15 minutes of warm up, vertical syncs perfectly and stays OK
until set turned off. Freeze spray, hot air, etc around vertical
output circuit and Jungle IC (LA7676) have no effect. There is never a
heightproblem or a linearity problem. Have not been able to find any
bad capacitors in either area. Is this a known problem. If so, what
is the fix?

I had a similar problem (different set), turned out there was noise on the
12V rail which caused a loss of vertical sync. Take a look at the caps
around the powersupply.

On my set the 12V was generated from the flyback and replacement of the
highspeed diode corrected the problem.