Space Invaders reseting problem (watchdog)

n_yohan

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I believe that I have a watchdog problem on my Space Invaders cab that I am restoring. If I plug in a Space Invaders Deluxe sound board the game plays fine. With the Space Invaders sound board it just keeps resetting at the exact same point just a few seconds into the demo screen.

I can coin up the game and hit the player 1 button and the game works but then just as you are about to be able to play it resets again. I believe the problem is the watchdog on the sound board because the other sound board for deluxe work great.

Does anyone have any idea what part needs to be replaced on the sound board to make the watchdog function?
 
The watchdog *is* functioning. Its "barking" to tell you there is a problem. In this case, its on your sound board.

Any idea where I should start looking for the problem? I could replace the caps on the board easy enough but after that I'm not really sure where to start looking.
 
Not cap related. I'd be looking to the rom chip select lines first. Its only getting so far into the code before it resets. Something bad on the soundboard can affect the operation of the main board since you still have data and address lines going there. So someone with logic troubleshooting skills needs to track down the problem.
 
Which ROMs do you have on the motherboard? I'm not sure if SI and SID have the watchdog reset at the same location. That is, you may need to have the proper ROMs on the motherboard to match the daughterboard you plug into it.

Mebbe I'll pull up the mame source to see...
 
Not cap related. I'd be looking to the rom chip select lines first. Its only getting so far into the code before it resets. Something bad on the soundboard can affect the operation of the main board since you still have data and address lines going there. So someone with logic troubleshooting skills needs to track down the problem.

When I first powered the board on the Tantalum cap under the heat sink smoked and the game made a lot of noise. I have replaced the Tantalum cap and now I have the problem that I described. Assuming that the problem came from that bad cap, the line goes from the connector to the cap then into the chip that has the large heat sink in the bottom left corner (as the board sits plugged in). So my guess is that maybe that chip needs to be replaced. Any idea what chip it is?
 
Thats the audio amp. I doubt the Tantalum meltdown affected it. They tend to do that when they get old...you never know when one will go exploda-pop....
 
Which ROMs do you have on the motherboard? I'm not sure if SI and SID have the watchdog reset at the same location. That is, you may need to have the proper ROMs on the motherboard to match the daughterboard you plug into it.

Mebbe I'll pull up the mame source to see...

It's the regular space invaders roms. From what I have read, you can use a SID sound board in a SI game board but not the other way around.
 
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