Sharp EL-5100S - Battery Drain

[Jeff_Birt]

There is not much inside these, a processor and 3 LCD drivers plus a handful of caps, resistors, etc. The first thing I would suspect is a little conductive gunk on the PCB where the batteries are. Coin cells do sometimes leak, though typically not much so it might not be obvious at first. Clean that area up with alcohol.

I've attached a picture of the power supply section. The 100pf cap is across the battery at all times. If this is leaking (become slightly conductive, not physically leak) it could drain the battery. Ceramic caps typically are not an issue but they can short circuit internally so it stands to reason that one could become slightly conductive.