A fairly new and well kept multimeter I own began to display fluctuating readings and otherwise acting unstable. I replaced the 9v battery with a fresh one and it was no better. I just bought some nickel-zinc batteries and some early designs would fail early from "dendrites" growing inside the cell during recharge. The more common term for "dendrites" of zinc is "whiskers."
Cheap lead free solder will grow whiskers on a circuit board and ruin the appliance. I have seen that happen to a windup emergency radio.
I took the multimeter apart and looked at the board and there were spider web looking white areas all over. Using a pencil eraser I removed them and now the multimeter works again.
I am glad I live in the US, where we still have access to decent 60/40 lead zinc solder. Solder with silver and copper is available for plumbing, but for delicate circuits, zinc eventually causes trouble.
