SNK vs CAPCOM Pcb Repair.
Hi Guys,
I am proud to publish my first repair post for a late "SnK vs Capcom" arcade pcb. These PCBs have been sold at the end of Neo Geo era (2003) and were sold in several forms. This one is Jamma "all-in-one" MVS PCB including both the game and the neo-geo mvs hardware (late hardware with few chips and the big Neo-GRZ one).
Board received and first test. Issue is confirmed :
The game actually is not booting. Sometimes the card reboots itself, displays weird things or simply displays a Wram error :
The message indicates the "lower" ram seems to fail.
5540 means 2 bytes for upper ram (55) and 2 bytes for lower one. In this case the lower one read is not equal to the expected ones. Well.
Looking at the ram pins with a simple logic probe shows no obvious issues. Looking at the trace continuity with the 68000 shows no error... I am feeling lucky...
Let's swap it (I was missing a oscilloscope today to confirm it is really bad)...
The chip has been replaced and it is time for a test....
Good news the card is now booting, ram is ok, sound is ok but image is crap. We can detect all graphics are bad (fixed layer, sprites, etc...). This is usually a cart connector that is dirty...but wait, in this case...there is no cart connector on the board as the rom chips are directly on the same pcb. Humm. Now using the best tool you can have : big fingers.
Purpose : try to find out a bad connection, or weak solder on graphic chip. Well, sometimes it works...
Done ! The board is back to life for 30 years ! 👌👍