My Space Invaders is not keeping my programming very well. The first that goes is the lowest of the high scores for replay. Though I set it to 460,000, within a few days of being off and on, the score sets to about 20,000. This is convenient in that it pretty much ensures a game each time you play, but it's annoying because if I let the machine sit for a few days without turning it on, it clears everything, including replays, high score and replay scores.
I discovered the battery that was installed before I got the machine is a 3V Lithium. I put a voltmeter across it when the machine was ON and got 5V. With the machine OFF I got .5V (yes, half a volt). I also found someone used a very poor job of soldering wires to the battery (a no-no by the way) and then to the board. I used a set of diagonal cutters to snip the wires and removed the battery. it doesn't appear to be a "rechargeable" battery either.
Checking a few things on-line, I see that some folks replace the battery with a coin-cell or other replacement 3V non-chargeable battery. I also see that in order to properly do that, a resistor needs to be changed to a diode, to prevent the system from attempting to charge the battery.
Inspecting my MPU, I find R12 is still installed... meaning it was never swapped out when this Lithium was put in. It's probably lucky it didn't explode at some point.
I am now in a position that I need to replace this battery. I found one place that offers an AA 3.6V rechargeable Ni-MH battery, but other than that, it looks like most are non-rechargeable. I stopped at a BatteriesPlus tonight but they wanted to sell me a rechargeable triple-pack for a wireless phone. I could have made it work but for $20 I figured there was something better to be had.
What is the collective wisdom here? Replace with a non-rechargeable and swap R12 for a diode? Or go with the rechargeable, and if so, what do you put in?
Thank you for the recommendations ahead of time.