Alright, I have an update for you guys.
First off, thank you a whole bunch for the reference to the ATX mod. It saved this machine so far!
When I booted it up first time with both bottom and top power supplies replaced, and no coin hopper installed, it turned on, cycled the reels, and then popped up with 800+ credits. It let me place bets and spin, and win. It was awesome!
Then I pressed the cashout button...
I heard some clicks, and then a 'HprJ' code had appeared. This was odd since it wasn't even installed.
I tried installing the coin hopper and then booting the machine again, this time it showed 'HprE'. I added some quarters, since its a .25 machine, and booted the machine again, but it presented the same error code, 'HprE'.
I'm digging in the manual now to find out what all the parameters mean in the menu. I want to try and make it a coinless machine until I can fix the hopper or replace it.
I have some ram clear chips for this machine arriving soon so I intend to do that as soon as I get them.
In the mean time, I will link a video of this machine as it first worked again and then now as this HprE issue persists.
Thank you again!