k4600 monitor issues pac-man

zapdbf

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I am working on a k4600 monitor I believe a 19k4676 tag is gone but the boards match to this schematic.
I am using the genie pattern generator on cross hatch and I have a horizontal issue I am trying to solve. when I turn up the raster to see the scan lines I notice that the start location for the horizontal scan lines are not in the same place for each line it forms a shape of a half sine wave very small but disturbs the vertical dot alignment.
here are a couple of pics with the raster tuned up. using a cross hatch pattern.
http://www.zapdbf.com/wave1.jpg
http://www.zapdbf.com/wave2.jpg

picture is steady and not moving. this was after horz and vert adjustments so they could be way off. but I scoped out the h sync signal and it is present after the sync amp. but the waveform just before the horizontal oscillator is present but incorrect the timing is correct but the pattern it's self has a capacitor discharge curve look to part of the wave form and this is missing, I checked all caps pertaining to this circuit and they are testing ok. The waveform is also not very steady at that test point. the horizontal amp transistor checked good with no leakage.

fyi, all the electrolytic caps were changed by somebody else, I rechecked the caps using the part list and checked polarity and all are fine.

anybody got any ideas?
 
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btw this is the first time I have used the genie I believe the setup is cga for this monitor. in the pac-man machine the picture has the same issues.
 
hi, looks to be the horizontal hold is out of adustment, you have two adjustments on the x/y card. the one you can see is for fine tuning and there is one in the middle of the x/y card, its the silver box that takes a flat head adjustment tool. see pic1
 

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yes i tried that it adjusts the horizontal oscillator free running frequency. The circuit looks like a type of Hartley oscillator.
 
I belive the Genie outputs POSITIVE sync. Do you have the correct video interface card in the monitor? Is the sync wired correctly to that card?

There are many variations of the video sync card ("Pxxx" number) and the pinouts are different.
 
the default wiring of the plug i believe is going to the negative sync. yes it is a 317 card.
i did do a quick check of the connections and the rgb ground and sync were in the same locations as the pac-man machine.
so i assumed they were correct since it came with that plug. but i will need to investigate further.
i was looking at this earlier and i am pretty sure both the pac-man and the genie are going to the negative sync.
 
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yes both the pac man and the genie are going to the negative sync. p203 pins 2 and 3 on the p317 IF card. Is pac-man using the negative sync ? the wiring suggests that but I am not sure if this is the original monitor or not.
 
thanks, i will try the positive sync tonight.
If this works than (i think it will) i must have either a neg sync input issue in the monitor, or a composite sync issue coming from the pac-man board. I did do a quick check of the sync coming from the pac man board and there was a pulse but not sure what it is supposed to look like.
i am assuming similar to an ntsc signal with the video components removed? At that time i did not realize it was a composite sync signal. both sync pins had the same sync pulse i was just checking for a signal not what it was supposed to contain. but i remember seeing only one pulse the scope was set on vertical triggering so it was a 60 hz pulse. i must be missing the horizontal pulse i am assuming 15khz ?
do you have a scope pic of the composite pulse coming from the pac-man board?

the Genie did not come with much technical information so i was somewhat in the dark.

thanks for your help
 
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The Wells-Gardner "Genie" pattern generator and it's clones made by B & K and GME come with virtually zero information about them.

For normal arcade monitors you set the switch to "CGA" mode on the front panel of the Genie.
 
Ok, this is what happened. I changed the sync pins to the positive sync inputs. Neither the horz or vert would lock in. so i then put it back into the negative sync. vertical locked it well and one other thing i noticed was actually the horizontal was locking in as well because even though the screen looked like it was horizontal sync out. the picture was steady i mentioned this earlier. The horizontal sync pulse was affecting the picture. That got me thinking about the horizontal oscillator. after scoping this out it was running way to high. but the slug for L351 was in about the middle of it's travel path. I would think that engineering would design it like this. Well anyway i screwed the slug down into the coil all the way to the bottom of it's travel path and it synced in great.

This is not a fix because i can't believe that it would have to be adjusted all the way to the end of it's travel path. Probably one of the caps like c356 is out of tolerance. I am going to change them out and see if this fixes the problem.
 
i can see that, but in my case, i installed the monitor back into the game and it works. After a good degaussing the picture looked pretty good.
Thanks for your help!
 
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