On Wed, 25 Jul 2012 09:28:06 -0500, Pete C. wrote:

Winston wrote:

My DW9118 charger emits a loud ~10 KHz audible tone when charging a
battery. It didn't use to do that. Anybody else have one of these?

--Winston

Deterioration of lacquer on a transformer / inductor in the switching
power supply?

In a past life, I troubleshot switch mode supplies for a living.
This symptom is more consistent with deterioration of filter component(s)
in the feedback loop, though I do see a *lot* of elastomer gunk
surrounding a couple filter inductors and other parts on the PCB. This
uses a custom Zilog chip, (the 4448 AKA B&D1999XRL) on a board made by
Delta, the power supply folks.

I don't see any documentation for this on the net and it's faster to toss
it and buy a Makita, though I'm tempted to draw a schematic for it.

--Winston