Samsung TXN3245FP - poor voltage regulation

[Mike Elliott]

I've ordered the service manual for this model TV. It seems that the
voltage regulator that powers the part of the circuitry that controls
vertical height need stiffening -- on bright scenes the vertical height
shrinks. On dark scenes, the picture expands sufficiently so that
"headline tickers," such as are seen on the bottom of stations like CNN,
are below the bottom of the screen.

I'm not a TV service repairman, but have good electronics knowledge, and
a vague grasp of the bits in a TV. I could use some pointers, if anyone
has the time, on what power supply to look at.

Yeah, this is kind of vague, but you never know when someone knows some
trick that does the job.

I can scan the relevant portions of the circuit diagram and e-mail them
if anyone wants to dig into this issue. Drop me a note.

j.michael.elliott(AT)adelphia(DOT)net

 

[Jerry G.]

This may be more of a high voltage regulation fault, than the main power
supply. You can verify the supply by monitoring the output voltages while
the fault happens. If the supply is fairly stable and the picture is
blooming, then you will know for sure that the fault is more in the high
voltage than the main supply. The main supply can vary as much as about 2%
to 3% during normal operation.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
Instruments http://www.zoom-one.com/glgtech.htm
=========================================


in message I've ordered the service manual for this model TV. It seems that the
voltage regulator that powers the part of the circuitry that controls
vertical height need stiffening -- on bright scenes the vertical height
shrinks. On dark scenes, the picture expands sufficiently so that
"headline tickers," such as are seen on the bottom of stations like CNN,
are below the bottom of the screen.

I'm not a TV service repairman, but have good electronics knowledge, and
a vague grasp of the bits in a TV. I could use some pointers, if anyone
has the time, on what power supply to look at.

Yeah, this is kind of vague, but you never know when someone knows some
trick that does the job.

I can scan the relevant portions of the circuit diagram and e-mail them
if anyone wants to dig into this issue. Drop me a note.

j.michael.elliott(AT)adelphia(DOT)net

 

[Mike Elliott]

This may be more of a high voltage regulation fault, than the main power
supply. You can verify the supply by monitoring the output voltages while
the fault happens. If the supply is fairly stable and the picture is
blooming, then you will know for sure that the fault is more in the high
voltage than the main supply. The main supply can vary as much as about 2%
to 3% during normal operation.

Jerry, thanks for the info.

Interesting to me is that the picture width does not change like the
height does when the picture blooms.

Could another possibility be that there is something amiss in the
vertical amp? Or do horizontal amplifiers typically operate differently,
making them less sensitive to high-voltage power supply changes?

The TV is less than two weeks old. Hard to tell from here if this is a
design flaw or a faulty set. I could kick it back. Maybe easier to
wander into the store and see if the floor model exhibits the same problem.

MikeE

 

[Jerry G.]

If this is a new set, you should definitely take it back. It may also be a
design problem, where they are cutting costs, and are using poor regulation,
or whatever...

I interpreted as the pix was blooming both H and V. Since it is vertical
only, this would be the low voltage supply or in some sets part of the
vertical supply is taken from the horiz output secondary. There are a
number of scenarios that can happen here.

Most of the lower cost sets have the effects where the raster will change
size with large changes of contrast and or brightness. Many of these sets
will also have the beam focus change a bit as well, when the pix intensity
changes.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
Instruments http://www.zoom-one.com/glgtech.htm
=========================================


in message

This may be more of a high voltage regulation fault, than the main power
supply. You can verify the supply by monitoring the output voltages while
the fault happens. If the supply is fairly stable and the picture is
blooming, then you will know for sure that the fault is more in the high
voltage than the main supply. The main supply can vary as much as about 2%
to 3% during normal operation.

Jerry, thanks for the info.

Interesting to me is that the picture width does not change like the
height does when the picture blooms.

Could another possibility be that there is something amiss in the
vertical amp? Or do horizontal amplifiers typically operate differently,
making them less sensitive to high-voltage power supply changes?

The TV is less than two weeks old. Hard to tell from here if this is a
design flaw or a faulty set. I could kick it back. Maybe easier to
wander into the store and see if the floor model exhibits the same problem.

MikeE

 

[Mike Elliott]

Thank, Jerry, for the tips.

MikeE