Road Blaster help needed

[fa001]

I have a Roadblasters upright game that when I first turned it on, it came up but was missing some graphics.  So I pulled the cartridge out to inspect it. I found that it had be "repaired" once before because there was a ground wire added running between one row of ROMs. But there was also a chip missing. At board location 4/5A there was supposed to be a 74S138 that is labled PSL on the schematic.

So I tried to reseat the ROMS and put a 74LS138 (thought that would be close enough) in the empty socket.  When I plugged the cartridge back in I got the "No Cartridge" error message on the screen. I took it back out and removed the 74LS138 but when reinstalled I still got the "No Cartridge" message.

Any suggestions or anyone out there fix these cartridges?

Here is a picture of the area of the board.  In Red is the missing chip and in Yellow is the added ground wire.

[SavannahLion]

Umm... did you do research before making those assumptions?

That IC is supposed to be missing and the jumper wire is supposed to be there. I found a similar (if not identical) board at http://heffa.net that shows the same jumper and missing IC.

Here's a pic (my apologies to heffa about the direct link)


Fixing PCB's is not my forte so I'm not sure what you can do at that point other than systematically examine and check the board starting by following the traces from where you plugged in the 74LS138.

[fa001]

Well the assumption was made based on the schematic. The chip seemed to be necessary to address graphics. But perhaps someone else knows for sure.

BTW, I did research the board and found a couple of pictures that did show the chip in place. Your picture is the first I have seen with it missing.

Does anyone know if there is a problem replacing a 74S138 with a 74LS138? Or if this chip is really necessary on this board?