TECH: ROM's and CPU show 4.35 volts???

cynic1

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Hello members,

I recently picked up an Outrun game. I installed a new switcher, and I get a solid 5V at the harness. When connected, the screen flickers constantly and I hear "check point" and various other speech. A check of the voltage at ROMs and CPU shows a steady 4.35. I did get the test screen comes up briefly. The ROMs and RAMs all tested GOOD. Does anyone know what on an Outrun PCB, or any PCB for that matter, would draw the power away from the Rom's like that? I imagine I need to get to a solid 5V on the ROM's before I can figure anything else out. Any help would be greatly appreciated.

Thanks in advance,
Shawn
 
That sounds like a large drop, but it depends on where your testing from. Forget about at the harness, that doesn't matter, test on the board two chips, one as near to where the power connects, and one as far away as possible (on the back of the bottom board if it's a double layer pcb).

You can't have any chips anywhere too high or too low or you can get problems, the most I'd go is 5.1 volt near and 4.9 volt far.

If you can't adjust the power supply to get into that range, you can try soldering in +5 and ground wires from the power connection (or a point on the board nearest), to a point at the far edge of the board, effectively giving the board power inputs at both ends.

If you still have too much drop after that then it's either a dodgy power supply or an issue with the PCB like an old, failing capacitor(s).
 
Thanks for the help on my Outrun

Hello,

Thank you very much to the guys who tried to help me with my Outrun PCB. I ended up changing PS's (another new one) and resoldering all the +5 and GND on the PCB. The board now holds the +5 at all IC, but I just get flicking on the screen. Coins up, but the start button doesn't light. When I go into test mode, the brake, gas and steering wheel don't respond and the "arrow" just keeps moving. Steering wheel has no control. Lots of problems. But thanks to the guys who tried to help me. I'll keep people informed if I get it going.

Thanks,
Shawn
 
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