Midway Space Invaders - Horizontal Scrolling

rob13s

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I've recently purchased an upright Midway Space Invaders cabinet which I'd like to restore to working condition. This is my first experience with an arcade cabinet.

After cleaning it up and re-seating all of the connectors, I was able to get the game to the point where it will power up and appears to work and play, with two exceptions - no sound, which I'll deal with later, and the issue I'm trying to resolve now: the screen just rolls quickly, horizontally, from right to left. You can see that the game is otherwise working; the attract screens work, and if you drop in a quarter, you can start the one player game and it appears to play ok.

My first thought was that it was a monitor problem, but after some basic troubleshooting I'm not sure that's the case. When I bought the cabinet, it came with a second motherboard / daughter board set. I think the spare set is from a cocktail version, as it has extra connectors which I've come to understand are for the extra player controls. I swapped out the boards, and all this spare set does is slowly flash four invaders on the screen on and off.

However, with the second board, although it's entirely useless from the perspective of playing the game, the monitor display doesn't roll at all - it's solid and steady. So if this second board can create a solid display, it can't be the monitor, right? But what could be wrong with the first board that would cause the horizontal sync to appear to be lost?

Any guidance anyone has for what I should be looking at would be greatly appreciated. I've read through as many of the relevant posts on this machine as I could find, and I will go through the power supply troubleshooting steps tonight - based on what I'm seeing, though, I guess I don't expect that to yield much for this particular problem (not that I really have any idea what I'm doing!).

Thanks!
 
You may want to look over the monitor section, the stickey at the top. I don't really know that hardware but it may just be a horizontal adjustment, but don't take my word for it and start adjusting anything.

Check all wiring and look close at the monitor wiring. Check all voltages and adjust for proper voltages.

Post a pic of what is on the screen.

I have read threads where someone just looked at a pic of the problem and knew right away that the problem was a communciation problem between the cpu/video board.

maybe wiggle wires too, while power is off and DON'T touch the suction cup thing on the side of the picture tube...on or off.
 
SI is vertical so you want to check the vertical hold if it's rolling sideways.
 
I'm having the exact same problem. Recapped with bob Roberts m7000 kit an it didn't go away. Should I replace the pots? When I adjust it just starts going the other direction and when I finally do get it to hold its half the screen split in two. It's driving me nuts!!
 
If the monitor locks with a different board that board would probably need repair...sync circuit not right. Does it seem to play at the right speed?

You can double check the monitor by connecting up a composite video source like a vcr or old game deck or something.
 
If it has a Wells-Gardner brand monitor, they have a vertical hold pot.....might just need to be tweeked.

Edward
 
If it has a Wells-Gardner brand monitor, they have a vertical hold pot.....might just need to be tweeked.

Edward

It's a Motorola m7000. It does have the vertical hold pot. When I adjust the pot it seems overly sensitive. Thats why I was wondering if I should just try and replace it. Also sorry for hijacking this thread, just didn't want to start a new one for the same old problem.
 
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