Mark Kaufer wrote in message news:8txdb.3861$hp5.1197@fed1read04...
I ... left some really old batteries in it and they leaked
inside of it.

What kind of cells? If they were zinc-chloride, aka "heavy duty"
cells, the electrolyte can eat up the etched circuits on printed
circuit boards. If they were alkaline cells, the electrolyte really
does no damage at all. The electrolyte in zinc-chloride cells is
acidic. So is the electrolyte that is used in lead-acid batteries,
which is sulphuric acid. The electrolyte used in alkaline cells is
alkaline. It feels slippery, like a weak lye solution.

I repaired my sister-in-law's analog Sharp SW radio, which had damaged
by leakage from zinc-chloride cells. I had to wire in some jumber
cables to replace the corroded traces. On the other hand, I've seen
lots of radios with leaking alkaline cells. I wiped off the
electrolyte with a cloth moistened with soap and water or a toothbrush
to reach the parts that could use some scrubbing, and the radios were
good to go. Sometimes I use a little baking soda too, but that's just
to give the radio that extra fresh smell.