Help, I'm going crazy.. (Defender Blue Screen)

AndyD421

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Okay, so I got a Defender a few months ago. Been working on it while I can, but due to lack of funds and time, it's been a long ride.

So, when I got it, I reattached the power chord, and the game played VERY sporadically (double sprites on screen, etc) and then eventually just started showing a rug pattern. The previous owner mentioned a ram problem, so I purchased a confirmed working RAM board from one of the great KLOV'ers on here. It didn't fix the game.

His knowledge led him to believe that I had 4116's bad on the main board... which seemed very believable. He directed me to switch a few around to see if anything changed... and it did. So, I knew my RAM chips on the main game board were bad.

Fast forward to today. I just got a 4116 to 4164 kit in the mail with 24 brand new 4164's.. just installed the power adapter and chips, and booted to a nice blue screen... which is even worse that before. No repeated boot sounds like last time, not a hint of a rug pattern....nothing.

What am I doing wrong? I mean, I've dumped $80 into getting this machine working, and it is still DEAD... please help.

Also, to advise, I am without a multimeter.. It's back home in Atlanta... and I'm at college.
 
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Reseated a 4164 chip that had a leg sticking out (DOH!) and now I am....

back to having a weird half blue half rug pattern screen with the boot sound continuously repeating.


The RAM board's lights give one quick flash then shut off... not two to signify everything is going smoothly.
 
Have you checked the voltage to the boardset?

You should be getting a solid +5v

The best place to take the reading will be off the ram chip itself.

Report back with your findings.
 
Show me a pic of the CPU board please. I am old and forgetful, and don't always remember that Early ROM boards and Late ROM boards can't be swapped. They must match the CPU board.
 
I know everybody always says to convert those Ram, but I've always had good luck out of just repairing the ram that the board tells you are bad! It gives you error codes, swap 1 or 2 chips and the board is up and running.

My personal opinion is you've probably still got a chip not makng good connection, or actually in backwards, or something. You might try holding the board up and seeing if you can actually see down each chip to make sure a leg isnt' bent under or something on one of them, it's really easy to miss one little pin when you're swapping that many chips.

With all that said I agree with Dokert that it could be the voltage (and he'd certainly know)... but that usually doesn't give you a screen half rug half blue.
 
[sound of a broken record] Try recrimping the ribbon cables. It is obvious that you have pulled the cable several times and it is quite likely that you have pulled some of the wires loose.

Andre at Arcade Solution has a good tutorial on how to do this: http://www.arcadesolution.com/ribbon.html

Just skip over the replacing the ribbon cable parts until you hit the part about using the vise to crimp the cables.

ken
 
[sound of a broken record] Try recrimping the ribbon cables. It is obvious that you have pulled the cable several times and it is quite likely that you have pulled some of the wires loose.

Andre at Arcade Solution has a good tutorial on how to do this: http://www.arcadesolution.com/ribbon.html

Just skip over the replacing the ribbon cable parts until you hit the part about using the vise to crimp the cables.

ken

thanks for posting this link I have a stargate sitting in my garage I haven't had a chance to look at yet. this might just come in handy thanks YellowDog
 
Stargate has a different board set. While they are similar, they are not the same, so what is working here may not work in Stargate.
 
I am only getting 10.86 VDC going into the main board when I should be getting 12 VDC.

Also, I took some readings at the power supply. The board is putting out roughly 15 VDC when it should be giving me 12 VDC...
 
Sounds like a power supply rebuild in your future. Most likely cause from your description would be the voltage regulator ICs (LM723). Get some sockets and some new ICs and see if that helps.

ken
 
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