Bob Urz wrote:
in business. First check the primary and secondary for continuity.
My guess is you will find the primary open. Measure at the leads

My diagnosis was wrong, and even some of my observations were wrong. I
thought AC from the wall went straight in to the transformer, but having
taken it completely out now, I see that they merely are routed very
close to it. I thought I had better eyesight than that.

Primary has two wires (black and white). They have continuity.

Secondary has three wires, each of which come out in bare-looking (but
actually covered in thin invisible insulation) twin heavy solid copper
wires. All have continuity to eachother.

One (red) is definitely +12v (goes directly to the battery and to the
circuit board). Two heavy wires (black, white) go to big heatsinks on
the circuit board, to which MOSFETs are screwed.

It is at this point that I can tell you with absolute certainty that I
am out of my league. Monetarily, I have nothing to lose, although I
suppose there could be some physical danger here for me. I'd plow on and
learn something anyway, but having just spent a half hour following
circuits around, I have no idea how to do anything more.

Drat...this won't even get hacked into an inverter. The battery seems
ok, though, so maybe I'll use the battery for something and give up on
the rest. I think with the battery and a tiny float charger I've got, I
could build a DC UPS for my cable modem and router and skip AC altogether...