John's Arcade Forum - Classic Arcade and Pinball Collecting and Restoring Discussion Forum - RETRO MAME - Nintendo Vs Forum

Hello,
        Today i am finally getting around to the Eyes project. I have made a test bench with a good monitor i found and tested the power supply.  All thing checked good so it hooked up the pcb to test and adjust voltages on the board.  the 5V and the 12V both test good. So I hooked the game up to the monitor and have a garbage screen.  I then cleaned the legs on all the socketed chips and still the same issue.
         Putting the game into test makes no difference except for one time i got a row of Fs in the middle of the screen as shown below.
(http://i.imgur.com/6HTjXcN.jpg)


This is how the screen looks normally

(http://i.imgur.com/MSJ4D99.jpg)

So i am guessing ram or rom issue? Im guessing ram, but have no clue how to find out which one is bad short of putting sockets in for all of them and swapping in new ones. 
     Any help would be appriciated thanks!

As John would say "it's hosed"

Basically you have a (extremely common) board fault.
Could be RAM or ROMs or logic or a bad connection/bad socket(s) or broken track(s).
If you have no idea it may be better to look for someone who can do repairs and send it to them.
If you want to fix it yourself you need to buy some basic equipment and research info on doing PCB repairs for at least 1 month or 1 year or 10 years. Watch PCB repair vids on youtube (Adam has a few good ones), read books about PCB repairs, including arcade manuals and figure out how to read schematics. Read books/datasheets about how logic chips work. etc etc etc.
Then get a junker PCB and practice on it.
At the very least you need a logic probe, multi-meter, pointed cutters, soldering iron, solder sucker, new DIP sockets, EPROM programmer and preferably schematics for the board you want to work on.
As a starter check the ROMs against the known good MAME ROM-set using EPROM programmer.
If good, check clocks and activity using logic probe.
If good, check RAM.
If good you have a logic problem or broken track.

This post really needs to be stickied. The basic repair info above is common to almost every "My board doesn't work, how can I fix it?" type of question that gets asked all over the net.

Update to this. After a lot of reading and watching many videos on using a logic probe.

Got the hardware to check all the roms and 7D was bad.  I reprogrammed the chip and they all checked good, but no difference.  All the sockets have good connections so I checked the clock at pin 6 of the CPU and it seemed ok, logic probe showed the low and high lit up and pulsing, so i went on and checked the ram and noticed that none of them were ever being written to( WE pin stuck high). 

     So i followed all the ram write enable logic back to the CPU and it all seemed ok.  So something told me i should check the whole clock circuit where i think i am finally unto something.  All my research showed this PCB being very close to pacman so I stumbled across this.

http://lawnmowerman.rotheblog.com/logicprobe.html (http://lawnmowerman.rotheblog.com/logicprobe.html)

So I follow the clock troubleshooting and on pin 13 of the 74ls368 i notice I have a high pulsing signal instead of a high and low pulsing signal. So now i think I am unto something I'm just trying to figure out which part is bad, but I am hopping when I figure that out the game will at least try to boot. I will be updating with more progress, hopefully soon.