On Sat, 23 Nov 2013 08:20:19 -0700, Tony Hwang wrote:

Have you ever worked on car charging system and battery?

Yes. 13.8 volts is "normal" for an open-circuit voltage.
The voltage is highest after charging, and then goes down, over
time, depending on the type of battery.

If I were you I'd replace x-former and battery and start from there.

I have no qualms about replacing stuff, but, I am trying to
debug first, *what* needs to be replaced (other than the transformer,
which is on order).

Right now, I'm trying to figure out why the power supply board
has 0 volts across the PWR and GND pins, even with 13 volts at
the inputs.