wg k4600 no picture

[elcapitan]

Hello,

I'm working on a galaxian cabinet with a wells gardner k4600 in it.  It played blind when I got it, so I recapped it ... to no avail.  So I started investigating closer.

The interface card is a p317 which can take separate +/- H/V sync.  Galaxian, however, outputs composite negative.  I thought perhaps the wrong card had been stuck in.  On closer inspection it appears many components from the p317 have been removed.  My first thought is that perhaps this card was merely converting separate H,V to composite sync so someone cleverly figured out how to bypass the circuitry and push the composite through.  I'm no ee, though, so I'm not confident I could verify this with the schematic.  What I have discovered is that the machine appears to have been wired up with the composite fed to both the H,V negative sync.  I can list the missing components from the interface board if anyone would like to share in the puzzle.

So I have no picture and I'm not sure what to do about it given the weird state of things.  The heater's glowing and the guns are whining.  The degauss appears to work and when i touch the screen i can feel the static electricity.  When I pull the looped H,V sync connection the whine changes pitch.

Anyone have a suggestion for where to go from here?

TIA!

[Ken Layton]

Galaxian originaly had Wells 4500 monitors and Electrohome wide chassis ("CAO") monitors in them. A few got the very first 4600's with the P297 or P302 video cards in them. Look on ionpool.net for my pinouts of these cards under Wells-Gardner as these early cards had different pinouts. At one time Midway issued a service bulletin detailing the harness wiring of Galaxian's video connector and the correct pinout of these early cards. Midway issued a small video connector adapter circuit board that took the original Galaxian video connector and swaped the video, sync, and ground to the correct pins for later (and modern) monitors.

A P317 video card was never intended for a Galaxian game.

[elcapitan]

What's in here now is a 19k4606.  So let's just assume some cretin replaced the monitor, couldn't get it to work, hacked on the p317 and totally screwed something up and after changing a few hands I now have it.  Sounds like my option is to plug in a p297/p302 and go from there?

Alternatively I could replace the missing parts on the p317 and find/make a board that converts composite negative to separate H,V?  Would that be easier?

It's too bad these machines don't come with a repair log.  It'd be nice to know how it got to this state.

[Ken Layton]

Look on the ionpool.net site at the Wells connector pinout and see what matches your video harness connector in your machine.

It might also be something as simple as the black level control turneddown too far on the video interface board or the screen control turned down on the neckboard.

[elcapitan]

I found your helpful pinouts on the monitor FAQ.  They're how I discerned something was not quite right with this setup.

Fiddling with the black level shows a dark screen or a bright green screen.  Somewhere right at the junction I can sort of make out a picture, but only for a fraction of a second.  Does that sound at all familiar?

[grantspain]

sounds like your contrast or colour gains are turned down-worth checking all your controls not just blk level first,you never know your luck

[Ken Layton]

Sounds like a bad black level pot, but I've NEVER seen one go bad on P317 board. That doesn't mean it couldn't happen though. I'd check the video preamp transistors on this board also to see if they are bad.

[20eyes]

Boy im glad i lurked in on to this thread, found some handy info. I've been working on a galaxian machine myself... I wasn't aware that they had k4600s as well.
The only problem is that after I did the cap kit I can't get the vertical sync to hold and I have no idea where to look for the problem. the picture will eventually hold for about 5 - 10  seconds (and its really hard to get it to do that) and looks really nice but then it starts to roll again.
I've been reading my randy fromm book as I go so i'm still learning...

I have a dead 4600 that i've been trying to revive in my spare time and that pinout list is just what ive been looking for.

Sorry to hijack an old thread.....