Build Your Own Arcade Controls Forum
Main => Monitor/Video Forum => Topic started by: jrodas on November 28, 2016, 06:22:46 am
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Hello,
I had a pincushion issue with my Hantarex Polo 28" monitor but the problem disappeared after replacing all the electrolytic capacitors, and adjusted the different potentiometers in both the pincushion board and the remote control board.
Now I have another issue. The total width of the image is narrower than the screen width regardless the brightness. I have tried adjusting the two horizontal coils (the two bigger ones, for adjusting the horizontal width and linearity if I'm not wrong). ONLY the bigger one (the one which is farther from the flyback, with a squared shape hole on the bottom part ferrite) make any effect on the image. This one can make the image horizontally narrower but not wider than the previous limit (again, I have 2 vertical black bars on the sides of about 1-2 cm, regardless the brightness of the monitor). The other coil (the one with a slotted shape on top to adjust it) has NO any effect in the horizontal shape.
I have replaced the TDA2593, all the small transistors BC548 and BC558 in the horizontal circuitry, and the big horizontal output transistor BU508, to see the impact in the horizontal shape and width of the image. They were in good condition previously and they have no impact to solve this width issue.
I also clarify that after adjusting the pincushion until certain width, I can make the image straight/rectangular (not oval), but when I move the horizontal scale potentiometer (at the remote board controller board), the central part of the image doesn't make wider but the top and bottom sides YES, making the image curvy after reaching this 1-2cm black bar distance on the sides.
Any advice on how to continue improving this?. ???
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is the ferrite core of the width coil broken
the other coil is the h lin coil(the one with the square hole)
have you checked b+ yet?
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The ferrite core of the width coil (the one slotted, not squeared) doesn't seem to be broken at all. I can screw it and unscrew it without problem with a plastic screw driver. The plastic female treaded part of the coil is also in good condition, as far as I can see... and I have turned the ferrite several times in each direction without problem and without any appreciable effect in the total width of the image (several millimeters deep, and about 1-2 mm over the plastic top). However, as I said, what it is really strange for me is that turning the linearity coil ferrite to the right about less than 90º I soon appreciate as the image total width decreases.
I haven't checked any voltage level yet!!, no the B+ or any other.
Where do you think I should start measuring, having into account that the width coil seems to have no impact in the total width?.
PS: To clarify it more, I temporary turned quite high the overall bright level using the lower potentiometer of the flyback, to easily appreciate any total width changes when using a mirror... With such a bright background I can see the limits where the image would start to flip over when move it to the sides. With this into account, at present I have always two thin vertical "black bars" on the sides, of about 1-2 cm wide, and I can only make the total width narrower, not wider than such limit. And, when I make it wider with the remote control potentiometer, the black part still remains in the middle of the image, but starts to be curved on the top and bottom of the image (resulting in a barrel effect, but with 2 black vertical parts still on the sides & center of the image). The only way to maintain it straight is to make it a little narrower horizontally :'(
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the fact the size coil is doing nothing should point towards the faulty component,possible faults could be c174,c175,d134,d135