Pincushion?

[solder lung]

My Alphascan 511 Sampo 15" monitor has a weird problem. The pictures on
the
link below describes the image problem. This is the farthest that I can
correct with controls in front. Resetting it to the default factory
setting just makes the image more unbearable. Brightness, Contrast,
Colors are good but I just can't seem to straighten the edges! .. and
so as the image also. Any suggestions? Is this a sign of a leaky cap?
in what areas should I start looking? Thanks in advance..

http://img.photobucket.com/albums/v249/celerino/alphascan511/DSC01665.jpg
http://img.photobucket.com/albums/v249/celerino/alphascan511/DSC01668.jpg
http://img.photobucket.com/albums/v249/celerino/alphascan511/DSC01670.jpg
http://img.photobucket.com/albums/v249/celerino/alphascan511/DSC01672.jpg
http://img.photobucket.com/albums/v249/celerino/alphascan511/DSC01674.jpg

-mike

 

[Franc Zabkar]

My Alphascan 511 Sampo 15" monitor has a weird problem. The pictures on
the
link below describes the image problem. This is the farthest that I can
correct with controls in front. Resetting it to the default factory
setting just makes the image more unbearable. Brightness, Contrast,
Colors are good but I just can't seem to straighten the edges! .. and
so as the image also. Any suggestions? Is this a sign of a leaky cap?
in what areas should I start looking? Thanks in advance..

http://img.photobucket.com/albums/v249/celerino/alphascan511/DSC01665.jpg
http://img.photobucket.com/albums/v249/celerino/alphascan511/DSC01668.jpg
http://img.photobucket.com/albums/v249/celerino/alphascan511/DSC01670.jpg
http://img.photobucket.com/albums/v249/celerino/alphascan511/DSC01672.jpg
http://img.photobucket.com/albums/v249/celerino/alphascan511/DSC01674.jpg

-mike

If this is a digital monitor, then I expect that its uP would be
adjusting the pincushion via an E-W correction IC. If you are
completely in the dark, then you might consider recording the part
numbers of the various ICs and searching the Net for their datasheets
or functional descriptions. ISTR there was a particular ST
Microelectronics IC (8-pin DIP?) that caused a few E-W problems in
some monitors.


- Franc Zabkar

 

[solder lung]

If this is a digital monitor, then I expect that its uP would be
adjusting the pincushion via an E-W correction IC. If you are
completely in the dark, then you might consider recording the part
numbers of the various ICs and searching the Net for their datasheets
or functional descriptions. ISTR there was a particular ST
Microelectronics IC (8-pin DIP?) that caused a few E-W problems in
some monitors.


- Franc Zabkar

There is on made by ST micro.. its a dual op amp LM358n.. i'll try
replacing this and see how it goes. thanks

 

[Franc Zabkar]

Franc Zabkar wrote:

There is on made by ST micro.. its a dual op amp LM358n.. i'll try
replacing this and see how it goes. thanks

I was expecting something like a TEA2031A, but that was just a WAG.
The E/W correction can be done in *many* different ways. You really
need to identify the various ICs. E-W correction works by varying the
current in the horizontal yoke according to the vertical beam
position. The current is at maximum when the beam is at the middle of
the screen, and minimum at the top and bottom of the CRT. What you
should be looking for is an additional coil or transformer in the
horizontal section that is driven by a parabolic signal from the
vertical section. For example, a model 4CM8270 15" Philips monitor has
an E-W circuit which is controlled from the "Vertical Parabola Output"
pin (11) of the TDA4850 H&V deflection controller IC.


- Franc Zabkar