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Non-working Street Fighter EX PCB


darkjedi

Question

So a while back I acquired a non-working Street Fighter EX PCB, and decided that 2017 is the year I start working through my hardware pile of shame. Not going into the board's history, or who it came from - just that it was allegedly sold "as working", but there was no chance of getting it returned/refunded.

 

So at the moment I'm getting nothing when the PCB is plugged in and powered up. Have tried in both my own cab at home (that has a SF2: CE CPS1 board in it currently), and on @Roxbury's test rig - in both cases there is voltage getting to various parts of the board, but we didn't get a picture or any other indication of life. There's no obvious signs of damage or bad tracks on the board, and we've also tried re-seating the various socketed chips to no avail. Sadly I don't have another ZN-1 based game to try swapping ROMs over from either.

 

Any suggestions on where to start with troubleshooting this sucker? Will post a pic of the actual board once I'm back at home.

 

Cheers

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The usual path for tshooting roughly follows this

 

1) Check voltages at the board

2) Re-seat all ribbon cables and PCB interconnects

3) Dump the ROMs, this has the added benefit of making you reseat all the ROMs, and it lets you look for missing pins, or historical hack damage inside the ROM sockets.

4) Fire up the logic probe, or Oscope and check the main CPU is getting a clock signal

5) Check that the CPU is not in /RESET (reset pin should be high if board is trying to run, or watchdogging (pin constantly going high and low)

6) Check that the CPU is not in /HALT (halt pin should be high if normal).

 

Then you follow where that takes you. If the board is watchdoging its worth finding out how to disable it before you try and troubleshoot a barking board.

 

7) If the reset and halt pin on the CPU are both high and stable, move on to the main system RAM and ROM, checking that the /CE and /OE pins are behaving and not clashing with each other.

8) Also look at the main system RAM data bus lines, you will need a scope to see if they are clean or a total mess, a probe will probably just tell you if they are activem, which is better than dead or floating, but its not conclusive.

 

Also worth checking with you have sync on the video output, that can tell you if you have any signs of life at all, but you'd need a scope for that as a logic probe won't notice the pulses as anything other than a constant logic LOW.

Edited by Womble
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Womble,

 

You forgot 0.5 - Look over the board very well for bent, broken, missing, corroded, leaking, or otherwise damaged components, including ICs backwards in sockets. Next look for scratches and gouges on the board and check them with a loupe and multimeter for continuity. Patch any damaged traces and replace any leaking or missing component, repair or replace broken/corroded components.

 

:)

 

Physical damage is always the first thing to check out.

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