Space Invaders Garbage

troxel

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Been following the SI threads lately, and am running into my own problem. I have a Midway SI, and it powered up to garbage. I checked voltages on the power supply and everything looks fine. Burnt the test rom, and has what looks like the number 1 in the window. Piggybacked every ram, and didn't have any change. Is it recommended replacing the 8080a socket along with the H rom socket?

Any suggestions on what to look for next?
 

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One of the last bad rams I had didn't have an effect when piggybacked either but showed it with the test rom.
Mine eventually had four bad ones, but the test rom would only show one at a time. So you'll need to figure out which one for sure it's showing now, replace it, and then see what comes up next.

Have you tried the grounding of pin 7 of each ram ?
I would start with the suspected ram #1 which would be G8.
 
my si had 2 or 3 bad ram. In my case piggybacking worked but thats not a guarantee that it will work for everyone.

FYI you need the info sheet about the test rom..

a number 1 DOES NOT indicate "silkscreened rom 1" is bad.. You need to find a rom map.. ill see if i can find it on my own...

i had a testrom and info sheet but ive been waiting for it to come back to me after borrowing to another klover.
 
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Thanks for the help, guys. The RAM map was included in the folder for the test ROM. I will replace g8 and see what happens. My guess is you ground pin 7 without the test ROM in socket H?

When I removed all ROMs, I had what appeared to be a good test screen. I had straight lines, and pattern changed when the slam switch was closed. Didn't have any dots or flickering going on.
 
My guess is you ground pin 7 without the test ROM in socket H?

Either way.
I would do it without the rom first though.

When I removed all ROMs, I had what appeared to be a good test screen. I had straight lines, and pattern changed when the slam switch was closed.

16 straight single lines like in this pic?
 

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Had a chance to come back to this today, and noticed when I removed the test rom, I was getting the 16 thin lines, but it kept cycling with 16 fat lines. I checked the power supply and came up with the following numbers:

+5.11 Vdc (can't go any lower)
-5.02 Vdc
+12.04 Vdc
RESET 0.018 Vdc.

Now my question is do I need to focus on the power supply?

Theron
 

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Turned the +5 higher, and still getting the same patterns. I originally had it around 5.3, but brought it back down thinking it was too high. Thanks for the confirmation. Any other ideas where to start troubleshooting?

Theron
 
The fat/thin bars indicate the board is 90% working - that means the reset line is good and your voltages are spot on so you're fine in the power supply dept.

When you put in the test rom, does it still give the little black box/ram error?

Have you replaced the rom socket and/or the CPU socket at all?
 
Orion3311-thanks for clarifying the power supply for me.

When the test rom was in I was getting what appeared as "1" (picture above). I forgot to order a 8080A when I ordered my RAM. I will start by replacing the 2 sockets on the 8080 and the rom. I won't have a chance to work on this for a bit, but I always appreciate the help.

Theron
 
Had a chance to work on this a little bit tonight, and made good progress. Rams 1, 7, G, and 6 were showing up bad in with the test ROM. Replaced all the RAM and the test screen came up. Switched back to the original ROMS and game was up and running.

Have to more problems to fix. The sound was going in and out and player two controls were not working. I would imagine the sound going in and out is easy enough, but what about player two not having any buttons do anything. Couldn't move left/right or fire.

Thanks again for the help. Excited to make some progress on this game.

Theron
 
Are you testing in an upright or cocktail, and is it an upright or cocktail board? If cocktail I'd check player 2's grounds on the controls, and make sure your dip switches are correct. Also the daughterboard should have 3 plugs going to it, all 3 should be plugged in.
 
It's an upright machine. That's why I couldn't figure out why player 1 worked fine and not player 2. I do have the three connectors to the daughter board.

Theron
 
Wait it's an upright but you have 3 connectors going to the daughterboard? For an upright there should only be 2 (even if there's 3 on the actual daughterboard, and if so its prob a Deluxe).

Make sure DIP switches 5-6-7 are ON.

Can you get a pic?
 
I have 2 connectors to the daughter card. Sorry about that. I changed the dips 5, 6, 7 to on, and now player 2 is working fine. Thanks again for the help. Now I need to figure out the sound issue. Looks like I need to look at the wiring and connectors next.

Theron
 
For sounds - check the 12v fuse on the power brick, clean it up if need be. Then check the 4 diodes near the plug on the power supply. They tend to roast/go bad.

On top of that, clean up the larger of the two connectors on the daughterboard.
 
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