In the early days of electromechanical pinball machines, keeping track of high scores was easy - there was a small white area on the backglass where a player could write their best score for others to see. Plus, the machine had a built-in memory to show you the last player's score - the score reels would stay as they were until the next game was started!
But as soon as pinball machines moved from using relays and steppers to using computers in the 1970s the game designers had a problem. Computers always forget everything as soon as they are switched off, so how do you keep track of high scores, game audits (coins through the slots, games played, etc) and game settings (pricing, replay levels and so on)?
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don't let this happen to your game! |
The solution was to add a battery to the main computer board (which lives behind the backglass) so that there was always power to the memory, even when the machine was switched off, and the machine never forgot anything. And ever since then those batteries have been causing problems, especially if the game's owner tends to forget things instead...
The first generation of boards used a rechargeable NiCd battery soldered to the main board. Great, you may think - unlike ordinary Duracell-type batteries there are no worries about it ever going flat or needing replacement. But, like everything else, after a while rechargeable batteries wear out, particularly if they are being charged for hours on end every day when the game is on. First they go "furry" around the edges and then go on to leak their internals all over the circuit board.
On some games the battery was near the bottom of the CPU board so you would expect the damage to be limited when this happened. No such luck - the chemicals inside decaying batteries are nasty things and give off fumes that rise up the board, turning the legs of chips green and rotting them through. Also, they get into the printed circuit tracks and gradually eat them, spreading around the board as they go.
That's one of the reasons why so many of those games are now using after market replacement CPU boards, like the ones that Sean described in his piece on Centaur in the Winter issue. (The latest generation of these new boards doesn't need a battery at all.)
The two circuit board photos show what can happen in a really advanced case of battery leakage. The chips shown are those nearest to the on-board battery holder but the ick has spread across almost the entire board, turning chip legs and even transistors into green mould and attacking the printed circuit tracks.
So, in part because of all these issues, in the 1980s the pinball machine manufacturers decided to move from using rechargeable batteries to regular AA cells. Good news, you might think - at least you can now change the batteries because they are not soldered to the circuit board and there are no more rechargeable batteries to wear out and leak.
But, inevitably, there are also some problems with using regular batteries. The first of these is that the original "springy" holders used in 1980s and early 1990s Williams and Bally games are not exactly reliable. They tend to lose their "spring" or the contacts off the ends, leading to the annoying "factory settings restored" or "adjustment error" messages each time you turn the game on because the batteries are no longer in contact with the holders.
Also, because you can't charge ordinary Duracells you only want them to power the memory when the game is switched off - you don't want the power from the game trying to flow into the batteries when the game is on. To prevent this there is a blocking diode on every board.
Normally, a diode only permits power to flow in one direction - in this case from the batteries to the game, not the other way around. However, if the blocking diode breaks down and starts conducting in both directions nasty things can happen to the batteries. This actually happened on my Banzai Run and I can report that the batteries swell up to approximately twice their normal size before gunging out all their internals. Not nice.
The final, and most important, problem with ordinary batteries is that they go flat. Not a problem as such, as all batteries will eventually go flat - you know that when you take them out of the packet. But it's remembering that and changing them for new ones before they do that's the trick.
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AFM's battery holder removed from the CPU board |
Otherwise, the flat batteries will leak their insides all over your game CPU board and you are back to exactly the same problems as with the old rechargeable batteries.
And remember – the battery holder is always planted bang in the middle of the most expensive board in your prized game, where leaking batteries can do the most amount of damage.
Why am I telling you this? Well, by now you've probably guessed who the forgetful owner is...
At Christmas I was spooling through the Pinball Ninja's blog www.pinballninja.com. It's a fantastic site and I take my hat off to the anonymous repairer who put the whole thing together - a photo documentation and complete explanation of each repair done to every one of 500 separate machines over a 360 day period. That's impressive! It normally takes me a year just to get around to one repair on my collection...
One recurring theme that appears in dozens of the Ninja's repair reports is battery leakage. It's probably the most frequently repaired single item. Reading all these accounts of the damage caused by flat batteries made me stop and think for a minute: When was the last time I changed the batteries in all my machines? My conscience was clear but I thought I'd better go and check, just to be on the safe side.
And sure enough, I opened my prized, second owner from new, never been on site, Attack From Mars and screamed Noooooo. For some reason I had forgotten it when I last did the battery changes and the batteries in it were leaking. It was still keeping all the high scores and settings, so I must have assumed that everything was OK, but the battery holder was covered in green ick and the damage had started working its way down onto the CPU board itself.
Don't let this happen to you! Replace the batteries in your machines every two years without fail. If you can't remember when you last changed them - and two years is a long time - then put a sticky note on the front or side of the machine, and maybe also set a diary reminder on your computer or mobile 'phone.
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installed in my Addams Family |
You should be able to change the batteries without losing all the stored high scores and settings simply by making the change with the game switched on so that power is maintained to the game memory throughout (though I've found that this method doesn't always work for me - hopefully you will do better). But even losing the high scores is better than losing a CPU board.
Remember - changing batteries regularly only costs a few quid but will potentially save you hundreds in board repairs.
An even better investment is a remote battery holder. Given that the game designers cunningly always placed the batteries when they can do the most damage the best thing to do is move them away from the circuit board entirely so that if they do leak in the future they can't damage anything except the (very cheap) remote holder.
Remote mounting batteries is pretty easy. You can buy a ready-made remote holder from advertisers in this magazine for not much more than a couple of sets of new batteries. They normally come with fitting instructions and use crocodile clips to attach to the battery holder on the board so it probably takes less time to install than a new set of batteries. Or if you have basic soldering capabilities you can easily make a remote holder for yourself for even less - the parts probably cost about a quid. As a useful bonus, attaching the batteries via crocodile clips also solves any problems you might have with less than springy battery holders on the older machines.
I'd also suggest putting the remote holder in a bag when you install it, just in case the blocking diode ever fails. Thankfully I had a remote battery holder already fitted to Banzai Run when this happened to me and while I had to throw away the remote holder the CPU board was untouched. And if you are fitting a remote battery holder to replace one of the early rechargeable batteries always fit a blocking diode in the wire from the battery pack, otherwise the game will still try and charge the batteries.
Finally, if you are reading this and thinking "I don't have any pinball machines with batteries on the CPU board" don't forget that the same solution was employed on all contemporary amusement devices including things like slot machines (some of which can be rather more involved if you are replacing battery packs so check the manual first) and video games.
So don't delay - go and check your machines NOW to make sure that the batteries don't need changing. Can't remember when you last changed the batteries? Change them now, using good quality brand-name batteries, put a note on the machine and set a reminder for yourself to change them again in two years time. And if your machines don't already have remote battery holders get that sorted as soon as possible. You won't regret it.
If, horror of horrors, the batteries have already leaked then get them out immediately and clean up as much of the mess as you can. If the green crust has spread to the battery holder get that out too and install a remote battery holder. If it's reached the CPU board consult a professional repairer for advice as soon as you can to prevent the damage spreading any further.
It may sound like a lot of hassle but it's all quick and simple to do and will stop you opening your machine one day and getting a nasty shock (and potentially a big repair bill).
