Midway Space Invaders Deluxe questions

bones3010

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I have a friend I'm trying to help by resurrecting his old SI. When I got involved all it had in it was the original high-voltage block, a hacked-up harness, and the original monitor. Not much to really work with. I ended up getting him an "untested" CPU board set and began the task of trying to decipher the harness wires and what went where. The guy before me apparently tried to get power running by using what appears to be a PC power switcher(!). I have no idea what he was thinking, so since I was having trouble locating an original power PCB I decided to try out a HAPP switching power supply like in the newer JAMMA machines. After making some basic connections next thing you know after trying to get some sign of life I plugged it in and promptly blew fuses on the high-voltage block AS WELL AS the little fuse inside the switching power supply! ...Clearly something is REALLY hooked up wrong here.

So I'm starting from scratch. After rechecking my work I'm hopeful that no surges made it to the CPU. But in looking over the schematics I'm wondering if it's even possible to get this thing running on a newer switching power supply since there are a bunch of wires labeled for things I'm not even sure what they do (i.e. "sense" and "com").

So my primary question is this: CAN this thing be resurrected using a switching power supply? And what do some of these odd wires plug in to?

If not, does anyone know of where I can locate an appropriate working power board for this machine? I look on ebay but there are 100 different space invaders power boards apparently, and none appear to be what I need, or are either untested, or confirmed not working.

Thanks in advance!
-Rob
 
So I'm starting from scratch. After rechecking my work I'm hopeful that no surges made it to the CPU. But in looking over the schematics I'm wondering if it's even possible to get this thing running on a newer switching power supply since there are a bunch of wires labeled for things I'm not even sure what they do (i.e. "sense" and "com").

So my primary question is this: CAN this thing be resurrected using a switching power supply? And what do some of these odd wires plug in to?

Absolutely! I recently made myself a little mini test-harness for my tech bench to hook up Midway 8080 PCBs (like SI Deluxe) to my test bench's switching power supply (as well as display on my color arcade bench monitor, and speaker, and controls). Your switching power supply will need to have outputs for +5V (of course) as well as -5V and +12V. The CPU (and some other chips) on these boards requires all 3 voltages to operate.

The "-SENSE" line: you can safely ignore it (leave it unconnected). The "COM" line: that's ground (common); you need to hook it up for the DC ground on the output of your switching power supply. You can also savely ignore the "TILT" line, the "COIN METER" line, and the "V AUDIO" & "V AUDIO RETURN" lines. The last two you will need to get sound, but for initial evaluation, it isn't really needed.

Another thing about the original power supply is that it had a "RESET" line which fed the game boards provided a little delay or something. I've had no problem with just connecting the RESET line to ground. (Ideally it should be high for a brief period of time, then pull low... but my experience is that it's not necessary).
 
Thanks Darren! Very helpful info!

Once I've gotten some replacement fuses for the ones that blew I'll try this out (including my power switcher! ...that one worries me. If something was so wrong as to blow something inside THAT, I hope it didn't blow anything on the PCB).

I actually just got a lead on an original power PCB too. If that one works out I may try going that route. I'll let you all know how it works out.

-Rob
 
Damn, forgot to type the most important of my thoughts earlier...

Before hooking power up to the PCB (again), get your DMM and check the resistance between each of the power lines (at the edge connector is fine) and GND (again at the edge connector). If you're blowing power supply fuses instantly, there's likely a short on the PCB. If you measure line 0 (or even just tens of ohms) don't bother powering it up... you'll just blow another fuse.

There's another SI thread that's been active in the past week or so about that very problem (a short 12V line on a SI board). If yours does have a short 12V line, consult that thread.
 
Damn, forgot to type the most important of my thoughts earlier...

Before hooking power up to the PCB (again), get your DMM and check the resistance between each of the power lines (at the edge connector is fine) and GND (again at the edge connector). If you're blowing power supply fuses instantly, there's likely a short on the PCB. If you measure line 0 (or even just tens of ohms) don't bother powering it up... you'll just blow another fuse.

There's another SI thread that's been active in the past week or so about that very problem (a short 12V line on a SI board). If yours does have a short 12V line, consult that thread.

Will-do, Darren! Thanks again for the insight!
 
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