My principle TV has worked ok for years, but has gradually developed
vertical overscan, especially at the bottom of the screen. (Weather
scrawls, etc are almost off the screen). I see no vertical height or
linearity controls brought out to the outside of the case as on older
TV's. It is a Zenith model SS1915W, but this model is not listed in
the SAMS index to get a Photofact. Is it simular to one that is
listed, or anyone have an idea how to adjust this. I know that it has
an IC to develop the various signals, I replaced that several years
ago, but don't remember its number.

wrote:
My principle TV has worked ok for years, but has gradually developed
vertical overscan, especially at the bottom of the screen. (Weather
scrawls, etc are almost off the screen). I see no vertical height or
linearity controls brought out to the outside of the case as on older
TV's. It is a Zenith model SS1915W, but this model is not listed in
the SAMS index to get a Photofact. Is it simular to one that is
listed, or anyone have an idea how to adjust this. I know that it has
an IC to develop the various signals, I replaced that several years
ago, but don't remember its number.



That problem is almost always bad electrolytic capacitors near the
vertical output IC.

On Apr 19, 5:44 pm, James Sweet wrote:
wrote:
My principle TV has worked ok for years, but has gradually developed
vertical overscan, especially at the bottom of the screen. (Weather
scrawls, etc are almost off the screen). I see no vertical height or
linearity controls brought out to the outside of the case as on older
TV's. It is a Zenith model SS1915W, but this model is not listed in
the SAMS index to get a Photofact. Is it simular to one that is
listed, or anyone have an idea how to adjust this. I know that it has
an IC to develop the various signals, I replaced that several years
ago, but don't remember its number.

That problem is almost always bad electrolytic capacitors near the
vertical output IC.

I had an old Zenith a long while back with no vertical adjustment pot
on the outside - but there was one on the inside. I opened it up and
pushed a 3 inch or so length of PVC tube over the pot spindle (one
size fitted, 3/8 in, I think.) Then I drilled a hole in the back so
that the PVC tube poked out - voila! An accessible adjustment - worked
fine.
A bigger problem is horizontal scan - most TVs overscan horizontally
and require the vertical to overscan, too, to get good circles. I've
never found a good way to set the horizontal scan... unlike computer
CRTs.
Cheers,
Roger
PS. Usual disclaimers about dangerous TV voltages - if you don't know
don't do it.

The problem is usually caused by electrolytic capacitors in the
vertical amp section going bad from age.

Don't touch any adjustments. Have the set properly serviced.


Jerry G.
======




On Apr 19, 4:41 pm, wrote:
My principle TV has worked ok for years, but has gradually developed
vertical overscan, especially at the bottom of the screen. (Weather
scrawls, etc are almost off the screen). I see no vertical height or
linearity controls brought out to the outside of the case as on older
TV's. It is a Zenith model SS1915W, but this model is not listed in
the SAMS index to get a Photofact. Is it simular to one that is
listed, or anyone have an idea how to adjust this. I know that it has
an IC to develop the various signals, I replaced that several years
ago, but don't remember its number.

On Apr 19, 9:41 pm, "Jerry G." wrote:
The problem is usually caused by electrolytic capacitors in the
vertical amp section going bad from age.

Don't touch any adjustments. Have the set properly serviced.

Jerry G.
======

On Apr 19, 4:41 pm, wrote:



My principle TV has worked ok for years, but has gradually developed
vertical overscan, especially at the bottom of the screen. (Weather
scrawls, etc are almost off the screen). I see no vertical height or
linearity controls brought out to the outside of the case as on older
TV's. It is a Zenith model SS1915W, but this model is not listed in
the SAMS index to get a Photofact. Is it simular to one that is
listed, or anyone have an idea how to adjust this. I know that it has
an IC to develop the various signals, I replaced that several years
ago, but don't remember its number.- Hide quoted text -

- Show quoted text -

Thanks to everyone who tried to help except for Jerry G. who assumed I
didn't know what I was doing so was no help!
I was hoping some former Zenith tech would have the schematic for this
model. I'll try the elect caps around the vertical, I already had to
replace an open one in the sound path sound, so should have looked for
that too.
Please note when I say I replaced the IC and the capacitor, I myself
did it!

wrote:
Thanks to everyone who tried to help except for Jerry G. who assumed I
didn't know what I was doing so was no help!
I was hoping some former Zenith tech would have the schematic for this
model. I'll try the elect caps around the vertical, I already had to
replace an open one in the sound path sound, so should have looked for
that too.
Please note when I say I replaced the IC and the capacitor, I myself
did it!

Overscan problems can be due to excessive supply voltage to the
vertical output. Some power supply designs output higher voltages as
their electrolytics dry.
However dry electrolytics get better when warm, so your overscan
problem should reduce after a while. You should also be looking at bad
solder joints, open resistors and bad potentiometers.