Midway Space Invaders Help Needed.

jeff412

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I just got a new Space Invaders. The voltages are good on the Power Supply and on the board. I tested for +12 and +/- 5 at the edge connector. I also tested them on the Power supply board. The monitor comes on, but it looks like vertical hold is all messed up. The game occasionally makes random sounds, but doesn't play. Any ideas where to start?

Jeff
 

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I just got a new Space Invaders. The voltages are good on the Power Supply and on the board. I tested for +12 and +/- 5 at the edge connector. I also tested them on the Power supply board. The monitor comes on, but it looks like vertical hold is all messed up. The game occasionally makes random sounds, but doesn't play. Any ideas where to start?

Jeff

Was it converted to a switcher or is it still the original power supply board?
 
Hard to tell from the picture... does it kind of look like this?
memtest-4.png


Could be bad RAM... The ROM sockets are also known to be flaky. And you'll want to check the reset circuit to make sure that it is working as well if you haven't already (instructions here)
Unfortunately there is no self-test on these boards, you could see if someone can hook you up with a test rom. Or if you get the Braze Multi-kit (which just happens to be on sale now) there is a test function built into it.

There is a RAM test you can do too. You have to remove the ROM chip at location H.

After removing the rom, power up the board. You should get something that looks like a series of parallel lines (like in this video):

If you get a picture like that, then the CPU and RAM is probably working OK. If you are not getting this even pattern, if there are breaks or dots on the screen, then there could be a problem in RAM.
I found this helpful: http://www.brentradio.com/images/SpaceInvaders/midway_8080_test.pdf and actually Brentradio's site has a lot of Space Invaders info.

On mine, I got the Braze kit, and it fixed the issue (I'm assuming it was flaky rom sockets or a bad rom chip)

Of course, you could always send the board to elektronforge, they can test it and repair if needed.
 
Thanks for the info. I haven't checcked the reset circuit. I'll do that today. I'll also get started replacing the sockets. That may not fix it, but it will at least make it more reliable in the future.

As far as the picture goes, no it doesn't look like that. It kinda looks like the picture in the video. Perhaps I have a bad ROM.

I'll let you know how it works out.

Jeff
 
Did you try taking apart the two boards and cleaning the edge connector? I was having issues with mine with some messed up graphics, sound and gameplay. That fixed it up.
 
Reset tests fine. I pulled H and the screen looks different, but it still looks like it's rolling. Where are the V-Hold and H-Hold on these B&W monitors. This is my first one.

Thanks,
Jeff
 
Yes, that's the first thing I did. Looks like someone replaced the female edge connector between the two boards. I reflowed the solder on it as well.

Jeff

Did you try taking apart the two boards and cleaning the edge connector? I was having issues with mine with some messed up graphics, so connund and gameplay. That fixed it up.
 
Looks like I have a Motorola Monitor. I can't find the Vertical and Horizontal Hold for this one. Is there a way to adjust it? I see Vertical Lin. and Vertical Size. Not sure what Vert Lin. is.

Jeff
 
The M5000 series doesn't have a vertical hold or a horizontal hold pot. Regarding horizontal hold, it's got a horizontal frequency adjustment. It's one of those silver cans with an internal ferrite slug type adjustments. You need plastic hex wrenches to adjust it live. Vertical is done with various transistors. The vertical linearity pot has nothing to do with vertical hold.

Edward
 
Yes I have the m5000. I looked at the manual and that's where I saw the vert lin and vert size. Maybe its a problem on the board that makes it look like it's. Rolling.

Jeff
 
I ordered the Brasington multigame and got the game up and running. The monitor is still rolling. By adjusting the Vertical linearity I can get it to slow to a stop, but I can't get it to lock in. It still continues to roll slightly.

Jeff
 
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