Toshiba 329P8M Vertical Linearity Problem (Help!?)
 

There is no year indicated on this TV anywhere. It is a nice 32" with
Surround Sound.

The vertical linearity has become so poor now that it is no longer
watchable, but otherwise the TV is great.

There is a black band at the bottom of the screen and the bottom
half of the picture is all squished.

I read the user manual and there is no mention of the vertical
linearity. I took the back off of the set and there is no vertical
linearity control there, so I assume that it must be adjusted in
Service Mode.

I did a web search and found a couple of ways of entering Service Mode
and tried them, but they didn't work. (The one where you press Mute
three times then hold down Mute and press Menu? There is no Menu on this
TV.) (The one where you hold down 9 and press Channel Down? Didn't
work.) (There was another one: Hold down F and press Right Arrow
pointing into a Circle and enter 1046. Didn't work either.)

Please let me know if you know how to enter Service Mode on this set or
how the vertical linearity should be adjusted.

Thanks,

Bruce

Toshiba 329P8M Vertical Linearity Problem (Help!?)
 

"Bruce Dow" wrote in message
...
There is no year indicated on this TV anywhere. It is a nice 32" with
Surround Sound.

The vertical linearity has become so poor now that it is no longer
watchable, but otherwise the TV is great.

There is a black band at the bottom of the screen and the bottom
half of the picture is all squished.

I read the user manual and there is no mention of the vertical linearity.
I took the back off of the set and there is no vertical linearity control
there, so I assume that it must be adjusted in
Service Mode.

I did a web search and found a couple of ways of entering Service Mode and
tried them, but they didn't work. (The one where you press Mute three
times then hold down Mute and press Menu? There is no Menu on this TV.)
(The one where you hold down 9 and press Channel Down? Didn't work.)
(There was another one: Hold down F and press Right Arrow
pointing into a Circle and enter 1046. Didn't work either.)

Please let me know if you know how to enter Service Mode on this set or
how the vertical linearity should be adjusted.

Thanks,

Bruce


The vertical linearity should not be adjusted - at this point in the game,
at least. There is a fault in the field output stage. This will almost
certainly be a defective electrolytic capacitor, particularly if the problem
has been getting progressively worse. Once this has been located and
replaced, there will probably be no need to carry out any adjustments.

If you don't have experience working on TVs, I would strongly recommend that
you take it to a reputable repair shop, as the power supply circuitry
employed in TV sets, is potentially LETHALLY DANGEROUS.

If you are OK with the safety angle, look for caps close to the field output
chip's heatsink. Replace them all if you don't have the necessary test gear
to check them properly.

Arfa

Toshiba 329P8M Vertical Linearity Problem (Help!?)
 

Some, if not many vertical deflection circuits use a push-pull
oscillator setup. One side may have failed I agree to check for bad
caps. If you do replace, try to find the same µf rating with a larger
case/higher voltage, if the PCB layout allows it. Be sure you stay
within the same error tolerance. This will put a beefier component to
possibly patch a circuit weakness.

Another thing to look for is the deflection yoke, or it's control.
While the yoke rarely goes bad, they do from time to time. Top and
bottom deflection should be more or less equal, so if you can isolate
the upper coil set from the lower, be sure they are recieving proper
voltage. If not, the output can be hampered by a variety of issues,
but think simple. I have run into a similar problem which was fixed
by simply repairing a bad solder joint for the yoke's plug on the
PCB. Any discoloration of the windings is an extremely obvious
problem.

What you likely have is a bad component, not a faulty adjustment.
Adjustments go out of shape very gradually as a result of wear. An
instant failure or a rapid one indicates a component fault. Forget
your TV's internal modes because even if you did find it, you will
not find such an adjustment.

Service mode simply kills vertical deflection for aligning guns,
adjusting color drives/chroma, and miscellaneous troubleshooting. All
service mode will give you is your entire picture compressed to a
single horizontal line on the screen. This is not what you are
looking for.

If you aren't proficient with electronics, take it in to be repaired
instead of meddling with controls that are already properly set. One
does not tweak-out the base vertical size adjustment to make up for
vertical collapse.

Toshiba 329P8M Vertical Linearity Problem (Help!?)
 

Also: An ESR Meter will assist you is checking the capacitors in the
Vertical and Supply Circuits, replace the ones that check deficient.
"Electromotive Guru" wrote in
message reenews.net...
Some, if not many vertical deflection circuits use a push-pull
oscillator setup. One side may have failed I agree to check for bad
caps. If you do replace, try to find the same µf rating with a larger
case/higher voltage, if the PCB layout allows it. Be sure you stay
within the same error tolerance. This will put a beefier component to
possibly patch a circuit weakness.

Another thing to look for is the deflection yoke, or it's control.
While the yoke rarely goes bad, they do from time to time. Top and
bottom deflection should be more or less equal, so if you can isolate
the upper coil set from the lower, be sure they are recieving proper
voltage. If not, the output can be hampered by a variety of issues,
but think simple. I have run into a similar problem which was fixed
by simply repairing a bad solder joint for the yoke's plug on the
PCB. Any discoloration of the windings is an extremely obvious
problem.

What you likely have is a bad component, not a faulty adjustment.
Adjustments go out of shape very gradually as a result of wear. An
instant failure or a rapid one indicates a component fault. Forget
your TV's internal modes because even if you did find it, you will
not find such an adjustment.

Service mode simply kills vertical deflection for aligning guns,
adjusting color drives/chroma, and miscellaneous troubleshooting. All
service mode will give you is your entire picture compressed to a
single horizontal line on the screen. This is not what you are
looking for.

If you aren't proficient with electronics, take it in to be repaired
instead of meddling with controls that are already properly set. One
does not tweak-out the base vertical size adjustment to make up for
vertical collapse.