Got a Defender that has issues

oppolo

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It powers up with no sound and displays a purple rug pattern. Checked incoming voltages via the Arcadeshop power supply adapter and have the correct voltages to the boards. Where should I look next?
 
It powers up with no sound and displays a purple rug pattern. Checked incoming voltages via the Arcadeshop power supply adapter and have the correct voltages to the boards. Where should I look next?

Carefully reseat all socketed chips and see if it changes anything.
 
Checked incoming voltages via the Arcadeshop power supply adapter and have the correct voltages to the boards.
If you're measuring voltages at the power supply you need to recheck them, normally by checking voltages at the corners of one of the ram chips. The sound board has test points on the board so you can check the voltage coming in to the board, and the state of the on board voltage regulator (the sound board generates its own 5v).
 
KLOV member Dokert sells Defender wiring harnessess i have heard they go along way in helping correct problems, you may want to pm him.
 
Ouch. That isn't even the rug pattern. If you have a logic probe you are going to need to spend some serious quality time with these documents (link) (link) (link) (link) your logic probe and your board.

The sound board is a standalone unit. It will run its internal diagnostics regardless of the state of the MPU board. As long as it is working and has power, a speaker and a volume pot, it will happily chirp away.
 
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Could very well be a bad ROM board ribbon cable. You can make a new one with an IDE cable from an older PC.
 
That is unlikely to be a ribbon cable issue, but it is always worth trying to recrimp the cable ends. That pattern looks more like the CPU chip may be not be running (either a bad CPU chip or the clock circuit is not working) or more likely the reset line is pulsing. That is why a logic probe or oscilliscope is required to determine if there is actually any life in that board before spending money on shotgunning random repairs.

ken
 
Since it will not cost a thing, I'm going to try the ribbon cable swap to new IDE cable material when I get home. I'll keep everyone posted of my progress.
 
Try pulling and reseating the video ROMs and the CPU as well. Once in a while that is all it needs is fresh contact with the socket. Not a lot of hope, but it is free to try.

ken
 
My friend got a Stargate a few weeks ago. Had the same problem. Turned out to be a ram problem on the cpu board. But then again, the Stargate hardware (rom board) and the 7-segment LED to help w/ the trouble shooting. If your cpu board has the old 4116 rams, you might want to consider converting them to 4164's. They run cooler and ease the strain on the power supply. Check out http://www.robotron-2084.co.uk/techwilliams4164.html for info on that.
 
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