Shadow Force arrived broke :(

rolins

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I just picked up a Shadow Force pcb, and when I powered it for the first time it it went through its RAM CHECK and said IC46 is BAD. After that it reboots back into RAM CHECK again and does this in a never-ending loop. I guess I'm gonna have to replace it.

Here is a picture of IC46. Where can I find this part?

shadowforceic46.jpg
 
I just picked up a Shadow Force pcb, and when I powered it for the first time it it went through its RAM CHECK and said IC46 is BAD. After that it reboots back into RAM CHECK again and does this in a never-ending loop. I guess I'm gonna have to replace it.

Here is a picture of IC46. Where can I find this part?

shadowforceic46.jpg

many times it is not the chip and a support chip. You really need to test the chip to be sure.
 
Agreed - many times failures listed in the self tests can be misleading.... But this is just a RAM chip. Nothing particularly special about it - it's a 256k SRAM. Should not be hard to find. In fact, a quick search turned up there :
http://www.ebay.com/itm/84256A-70LL-SK-INTEGRATED-CIRCUIT-IC-CHIPS-/190495604683

The difference in the part number is that yours are 100ns, these are 70ns - so, faster.

If you have a replacement chip, a quick way to test this is usually to piggyback the new chip on top of the old chip, making good contact with all the pins. If that allows the game to pass it's self test, then it's definitely the problem. If it doesn't work, it's not conclusive, because the chip on the board can fail in such a way that the paralleled RAM won't help, but it's still fun to try before sitting down to change out a chip.

Of course, start with the obvious stuff, make sure you reseat all the socketed chips on the board...

-Ian
 
Would these RAM chips work even though they're faster?

Agreed - many times failures listed in the self tests can be misleading.... But this is just a RAM chip. Nothing particularly special about it - it's a 256k SRAM. Should not be hard to find. In fact, a quick search turned up there :
http://www.ebay.com/itm/84256A-70LL-SK-INTEGRATED-CIRCUIT-IC-CHIPS-/190495604683

The difference in the part number is that yours are 100ns, these are 70ns - so, faster.

If you have a replacement chip, a quick way to test this is usually to piggyback the new chip on top of the old chip, making good contact with all the pins. If that allows the game to pass it's self test, then it's definitely the problem. If it doesn't work, it's not conclusive, because the chip on the board can fail in such a way that the paralleled RAM won't help, but it's still fun to try before sitting down to change out a chip.

Of course, start with the obvious stuff, make sure you reseat all the socketed chips on the board...

-Ian
 
You could try just touching up the solder on the chip..it could be a cold/loose connection.
 
You could try just touching up the solder on the chip..it could be a cold/loose connection.


Yeah, I tried that too. I applied slight pressure at different places of the pcb while its powered on. Trying to narrow down where the bad part is, but so far no luck.

Voltage at the jamma reads 4.9v so power is not issue I think. All the easy stuff i did already such as clean the pins of jamma edge and all the socketted eproms. So far there has been no change.
 
Replace the RAM... if it's still showing as bad then we can revisit the issue.
 
I found the problem wasn't the ram, but dirty pins on this square chip here. Had to pry the chip out of its socket with an awl. I clean the pins and re-seated it, now it working again. Whew. :)

I've gone through dozens pcb in the past and this a first time I've ever seen a socketted chip like this. Is there a proper name for this?

shadowforcechip.jpg
 
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