Ketsui crashes with no battery. Solved!

After having discovered what happens to Varta batteries if left unchecked, I decided it was best to remove them from all of my PGM Cave boards (Espgaluda, DoDonPachi Dai-Ou-Jou, Ketsui). Since I always use default settings and always play with coins, I figured there was no need to buy new batteries, only to have them fail sometime in the future, so I just left them off the PCB.

I continued playing without batteries for a few weeks, with no problem, and then yesterday after I powered up Ketsui, I got this crash. This looks very similar to the known "Freeplay" bug....only difference is with no battery my game was set to use coins, yet it still crashed!

In fact, once in this state, the game crashes every time I power it on, in exactly the same place, during the start of the "Demonstration" sequence. Now my thinking was: buy a new varta battery, and/or replace the ROM with the "Fixed" version. Given the fixed ROM has a *very annoying* lock-on laser sound change - that was a not an option. And I really didn't want to have to keep changing the battery like CPS2 games. So I investigated the crash further, and found the reason, and how to prevent it.

How it happened:

Ketsui will run fine without a battery as long as you DO NOT turn off the PCB during the middle of an active game. If you turn off the PCB while its still playing an active credit, this can potentially leave NVRAM in a corrupted state. And with no battery, the board seems to fall victum to this corrupted state, and crashes when it tries to execute the stored demonstration sequence.

How to fix if your PCB is stuck in this crash state?:

1. Insert a credit before the first demonstration cycle, and play normally. Then just remember to not power down the PCB during the middle of an active game.

- or -

2. Before powering on Ketsui, flip that red devil switch shown in the first picture. Actually you will need to hold the switch for a few seconds, then release, then power up the board. This grounds the NVRAM chip, clearing it of any data. Then power on the PCB and everything will work fine. Again, make sure you do not power off until after your credit ends normally.

[update]
So it seems option 2 above, using the red switch to reset NVRAM (and fix the demo crashing bug), didn't seem to work 100% of the time. So option 1 is really the only way to ensure your Ketsui doesn't crash without a battery: just insert a coin (or press the credit button) after booting up the PCB and all will be fine.
[/update]

And there you have it. Also note that ESPGaluda and DoDonPachi Dai-Ou-Jou have no problem powering off during an active credit....so those games run perfectly fine without a battery.