Original Space Invaders

Kawydud

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I purchased an original space invaders in very good condition. The original owner said the machine worked fine, then started displaying just garbage on the screen. I took all the eproms out and cleaned and reseated all the edges, there are no signs of any bad caps or resistors on any of the boards. I have attached a picture of what the screen looks like when its powered up. Has anyone seen this on one of these before? Thanks for looking.
 

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I must be in waaay to deep...since judging by the garbage I know what that problem is.

That's a reset line problem. There's a voltage coming from the power supply thats pretty low, like .4v or something like that, that's called the reset line. It actually connects through one of the top plugs on the daughterboard.

First things first, try re-seating the daughterboard a couple times, as well as the two (or 3) plugs on it. If that doesn't work, check the slam switch on the coin door, if thats bent or otherwise shorted and always closed - that will cause the same problem.

If none of that helped, then chances are the power supply needs attention. Look for cold solder points (on the whole power supply).
 
Down in basement doing tests right now, reset line voltage is way too high, getting 2.4volts dc. I am going to post a picture of what I think you are calling the slam switch. There was a piece of tape on it with some plastic holding one way I think. It looks like there is a wire missing as well. Is there a cap kit available for the power supply on this that will take care of the reset line voltage? Checked board over, all solder joints look good.
 
Here is the picture of what I think is the slam switch? What exactly was that supposed to do?
 

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Hmmm now I'm going to have to check mine - never saw a setup like that before! Make sure those two wires aren't touching though, it kinda looks like something was cut/modified and I see an errant hair of wire that could be shorting.

The slam switch basically reset the game if someone starts beating on the coin door to try to trick/cheat it somehow. Since it controls the reset line, if that switch is closed full time, the board will never run.
 
PS - if you have a clip lead you *could* try grounding the reset line to see what happens, if the board comes to life (should display bars if it has no roms in it), then you still need to properly fix it.
 
Down in basement doing tests right now, reset line voltage is way too high, getting 2.4volts dc. I am going to post a picture of what I think you are calling the slam switch. There was a piece of tape on it with some plastic holding one way I think. It looks like there is a wire missing as well. Is there a cap kit available for the power supply on this that will take care of the reset line voltage? Checked board over, all solder joints look good.

try tweaking (as in shoving) the wiring connection on the p/s and or having someone move it while watching the game, see if that changes anything on the screen. if so, i'd go over every solder joint on the pins for the connector just to be safe. what are you getting for your +5 measurement? that could be an issue as well. the reset is there to allow the +5 to stabilize before allowing the board to boot.
 
Here is the picture of what I think is the slam switch? What exactly was that supposed to do?


The picture you have looks like the back of the start button that sits between the coin slots found on some early midway coin doors. The space invaders I've seen usually have that hole plugged, so I'm not sure what it's being used for on your game.

The slam switch should be hanging off the coin door lock like this one
 

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Thank you everyone for all of the replies. I went through all of the voltage tests and adjusted the pots to get 5.0 volts positive and negative, the 12volt I could only get to 11.8 volts. I will try grounding the reset line to see if that helps. I agree that the switch I pictured above is missing a wire, just do not see where a wire is not connected.
 
I grounded the slam switch and powered it up, same garbage, but the garbage is not moving. As soon as I take the clip off I get movement in the garbage again. So I would guess that the problem is not the switch. I will take apart the power supply again and go over each connection. Would one of the caps or resistors on the power board cause over voltage on the reset line if they were bad? From what the previous owner said, the machine was working fine then started getting fuzzy on the screen, then garbage. Maybe a bad cap?
 
Here are the pictures of both sides of the coin door. The center button on the top of the coin door does work, thought it was a plug when I first saw it as well.
 

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Gone over and reseated all connections again, still same garbage on screen. From what I can gather I need to rebuild the power supply to fix the reset line voltage. I have checked all solder connections on the board and all look good. None of the caps look popped, but I guess one could be bad. Is there a specific part of the board that controls the "reset line" power that I should be looking at?
 
When you say you get movement on the screen, are you toggling that switch in the middle of the coin door, or the actual slam switch (near the lock)?

If its the slam switch - it might not be a reset issue, although I had a couple boards with that EXACT screen both were reset issues.

If you have no roms in the board, you should get some somewhat solid bars that alternate thick and thin. When you activate the slam switch, the bars should shift slightly on the screen. Thats how you know the CPU is functional and the reset line does something.
 
All of the roms are in with the garbage on the screen. I am grounding out the slam switch for sure, I see that my Pac Man games have it on the doors as well. I just did not know what the next step would be since the voltage on the reset line of the power supply is still 2.4 volts.

The original 5 volts were higher, I just turned them down to see if that may be the issue.
 
the voltage on the reset line of the power supply is still 2.4 volts.

That's an issue....it'll never boot like that. I'd dig through the reset circuit on the power supply.....it's only a couple transistors/diodes/resistors....and maybe a cap or two.

Edward
 
I know there are only a few components to it, trying to find a complete cap kit for it. Rebuilt my ARII board on the centipede that I have. Does anyone know of a complete rebuild kit for it, or should I install a switching power supply with the adapter that is offered?
 
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