Part 5: Nintendo Vs MDS-02-CPU PCB Repair

In this video we will repair a non-working Nintendo Vs. System MDS-02-CPU PCB. We will check the Rams using the Retro Chip Tester, fix a no red problem, find some bad 74LS04's and refurbish the rest of the board.

[@pledg]

Nice work! You have a good test board now for the others...

[@arcadelaboratory]

Yes indeed that will be a good board for testing! Thanks!!

[@waynegram8907]

What can't DSO measure IC chip select waveforms? Why was there several variations mods for the reset circuit?

[@arcadelaboratory]

I mean you need a Digital Analyzer to make sure all the outputs are working compared to the inputs. With a digital analyzer you can observe like up to 30 pins at once. With a normal scope you can do 4 if you have a 4 channel scope which is not enough to interrogate 5 inputs and 3 outputs. What I read and tested about the difference in the reset circuit the mods seem to isolate the ram battery charger circuit that actually feed one gate on the reset circuit. I think Nintendo engineers saw that the battery back up was not a feature that Vs. games would use and isolated any chance the reset would be affected by the battery backup circuit.

[@waynegram8907]

@@arcadelaboratory What is providing the "isolation" between the reset circuit and RAMs battery backup circuit? The Isolation mods would be what? it seems when the reset circuit was watchdogging resetting it would also ret the RAMs battery backup causing the RAM to whip & loose all the data.