Here is an explanation on Daves zaccaria site (www.zaccaria-pinball.com) on battery replacement. I have used the backup capacitors on my zac games when I had them.
The biggest worry with a Zaccaria CPU board is the NiCd battery pack used to maintain the CMOS memory when the game is powered off. This battery pack is mounted at the top of the circuit board, in the center. If it starts to leak, the battery fluid runs down the board and ruins every component in its path. If you have a non-working Zaccaria game, this is the first thing to look for. If yours is working and hasn't leaked, PLEASE get the battery off the board and either use a 1F memory backup capacitor, or mount a remote battery immediately. If the battery has leaked, Clay's web site has a good recovery procedure for dealing with the corrosion and damage. After cleaning up and neutralizing the leaked fluid, remove and replace all components that were touched by the battery fluid, and all sockets on the board. Inspect the connectors and ribbon cables for signs of corrosion and replace as necessary.
To replace the original battery, a 1F 5.5V computer memory backup capacitor like Jameco P/N 142957 or Mouser P/N 555-1.0Z5.5 can be mounted on the CPU board in place of the battery pack and short leads used to connect it to the battery (+) and (-) traces, or a fly lead can be connected where the battery used to be and used to reach a remote battery pack.
To mount a remote battery pack, cut two wires to about 16" long, and solder them to the battery (+) and (-) pads. The other end I solder to a .100" two-pin connector snipped from an old PC floppy drive controller. I add a drop of JB Weld two part epoxy, then heat-shrink the connector, forming a small plug that is just the right size to connect a Radio Shack rechargable portable phone battery (Part #23-197, 3.6V, 350mAh, NiCad). Mount the battery on the left wall of the backbox with a velcro strap stapled to the wood, and you should never have to worry about battery leakage again. Replace the battery every few years, just to be on the safe side.
Quoted from Thistle:
First off... I'm brand new around here and would like to apologize in advance for any gaffs.
I've just blown the dust off of a '78 House Of Diamonds that was in my house growing up and been under a drop cloth for 30 years. I have a 13 year old son that's super keen to get it running and he and I are going to (attempt to) tackle whatever it needs on our own.
I don't know why I expected it to just start working when we plugged it in, but other than the odd playfield light coming on, it wouldn't accept coins so we quickly turned it off and started our research which of course pointed me almost immediately to the battery on the board as our first culprit.
The battery is still putting out a slight current but nothing near the 3V+ it's supposed to and there is definitely some corrosion in the immediate vicinity of the terminals, but fortunately nothing seems to have travelled far and the surrounding components seem unaffected.
I've desoldered the battery and cleaned the board up and I believe we're ready to install a replacement.
I've ordered a CR2032 holder and what I believe is the correct diode (1N4148) to prevent battery charging, but this is where my question comes in.
Nowhere online have I managed to find a definitive and clear explanation of how these two components need to be connected. It's worth mentioning at this point that I have only the most rudimentary knowledge of electronics and desperately want to avoid harming the machine, but both my son and I are eager to learn.
Clearly if I was installing a rechargeable battery, I'd just connect the positive and negative terminals from the replacement battery to the spots on the board where the original battery was and we'd be done with it, but it's the location and orientation of the diode that has me stumped.
It seems that battery replacement is a very common operation so I'm hoping that somebody on here has some experience and tips for a pair of newcomers.
Thanks in advance!