Manekineko E6 error related to memory loss when left unplugged

[DaveG_66]

Hi, new to the forum, and need some info. A friend of mine dropped off an Aristocrat Manekineko Pachislo plus Daruma for me to look at, that he acquired during a move. It apparently was stored in a damp or wet garage. Other than some outside cosmetic moisture damage, dead spiders, and grime from bench grinder, it was thankfully complete.

When it’s plugged in and turned on, it shows a E6 error (nothing to do with the coin hopper), and after a typical reset involving the odds key, etc. it plays great. After doing some tests, it loses the memory setting approximately 20-25 seconds after being turned off and reverts to the E6 error when turned back on. In order to play it, it had to be reset every time it was turned on.

Then I discovered if I left the machine on in idle mode for several hours, it would retain settings for a longer period of time.
Suspecting a battery backup for odds setting was involved, I found a 5.5V 0.22F “super capacitor” located on the top board inside the front door. (I think this is the sound and input board)

So if my friend decides to replace the capacitor based on performance, and out of curiosity, a few questions:

-Is this the right location for the capacitor, or is there another in a different place?
-And, if the machine were left unplugged, how long does this capacitor hold a charge, assuming it has a good charge?
-And what does it take to make sure it’s charged completely, meaning how long should it be plugged in and on for a charge?

Thanks for any information, this forum has been very helpful and informative while doing a crash course on how to repair them. More questions about game settings may follow.