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Author Topic: PVM issues.  (Read 1817 times)
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KennyL
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« on: November 01, 2015, 04:57:09 pm »

Ian has had some communication with me already, but I decided to make this a post since it's easier to read and come back to than a PM asking him something.  Heh.  I did some further testing today.  I found every pot I could and tweaked it while the monitor was live.  I have pictures of the things I adjusted below, click them to see them larger on Imageshack.

The pot RV501 on the A main board turned out to be horizontal center.  I can adjust H center digitally in the menus as well, but not size which is the one I need.  The screen is far too wide and a bit pin cushioned.  Those adjustments don't seem to work either, but vertical position and such do.  So strange.  Here is a picture of RV501.  Look for the black shaft near the yoke wires.


I also adjusted the pot on the neck board, labeled C board, that was surrounded by a black cover.  Turns out this was horizontal separation of the color beams.  I tweaked it a tad and I could see red and blue on either side of the menu letters.  They're supposed to be pure white.  I re-tweaked it and I think it's closer calibrated that it was to start with, glad I messed with that.  If I can figure out the horizontal issue, the picture quality will be mint.  Here's a pic of the neck board,  The pot has a white shaft, look below the picture tube neck.


Lastly, I screwed with what I believe is the horizontal size coil.  It's a coil with an Allen style screw in the center and it's mounted on the yoke.  I adjusted it while the monitor was on and had a source hooked to the composite in and it did nothing when moved.  Below is a picture at an angle that shows the coil, look on the yoke and the coils are covered in white tape.


Also, I tested some points and the voltages seemed to be in spec, which didn't surprise me since the monitor will actually work and display a picture.  Something internally has caused the horizontal to collapse outward and not be adjustable.  I actually don't have a scope to test waveforms and I can only do a limited amount of probing until I get some better clip on test leads, but I guess I could just see if any resistors or diodes have bridged or went open.  I can print out the component lists and check them off as I go.  Time consuming as all hell, but worth a check I guess.  Start on the A board since it pretty well deals with all vertical/horizontal business.
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Kenny L.
As an f.y.i. there is more than corn in Indiana...there's soybeans, ha.
Mini NeoGeo machine thread, inspired by Ben Heck:
http://www.johnsarcade.com/forum/index.php?topic=2640.0
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