s+ battery keep going dead??

[slotmandave]

I have a s+ barcreast pinball slot and the battery keeps going dead after about a week , I put a new battery in and it dead again in a week . I don't leave the game on ?what would cause the battery to keep going dead?  Thanks guys

[CVslots]

Aside from the obvious (like insuring you are replacing the dead battery with a tested good batteries, good clean solders, etc), I would swap the MPU board itself with another one and see if its the board itself.

[slotmandave]

Thanks, That is what I thought to try next, went through 4 batterys in 4 months. Was hopping there was a different answer, like a power supply problem

[CVslots]

No, I wouldn't suspect a power issue.

[rokgpsman]

Also, the battery's only purpose on most mpu boards is to keep power to the cmos ram when the machine is powered off so that the bookkeeping data and other info stored in there doesn't get scrambled. We've had cmos ram chips go bad in a way that they drew way more power from the battery than normal, thus draining the battery much faster than normal. If your cmos ram is socketed you could try replacing it, usually just a chip change.

Another thing to watch for would be stuff on the board around where the battery is connected that would provide a path for it to discharge, like if there was a residue from a spilled drink or previous battery leakage. But since you've been replacing the batteries already you probably would have noticed something like that.

[therockinelvis]

I had one doing the same thing. Changed the CMOS chip and all was good.

[Badbaud]

On a few boards I have worked on I found the Tantalum capacitor above the RAM chip was leaky.

It is connected directly across the battery voltage and the RAM Vcc pin and Ground pin.

Probably put in there  for noise suppression or a detected power up problem with the design that was solved with a capacitor.

A simple test is to remove one leg of the capacitor and see if the battery lasts longer then it did previously.

After about 3 weeks I would say the capacitor was the problem if the battery still reads good.

Well, actually, use a DVM and watch across the capacitor and see if the battery voltage there is constantly dropping and never solid.

If it is dropping then raise one leg of the capacitor and watch the two solder connections the capacitor is mounted to and
see if the voltage levels out and stays steady.

[Midcoastsurf]

Double check to make sure both ends of your battery aren't grounded.  I had this issue on a pinball machine where someone soldered the positive and negative leads to the ground plane.  Batteries died in under a week and almost exploded.  Not sure if it applies to slots though...