On Sun, 07 Oct 2012 11:02:04 -0500, legg wrote:

On Sat, 06 Oct 2012 08:18:18 -0500, legg wrote:

On Fri, 05 Oct 2012 21:19:00 -0700, Jeff Liebermann
wrote:

snip
An unreadable schematic off the web assists in identifying functions
of most parts in the power train and drive cctry. Have been working on
switchers for some decades, so this section offers few surprises. I
can probably get function with a fixed value here, but am looking for
confirmation for a correct repair.

The unreadable schematic proves to contain a number of basic
connection errors. This is kind of reassuring; as drawn it made no
sense in certain areas. You see a capacitor in series with an emitter,
you know somebody's playing with you.

Extra PIC pins are generally just given pull-ups and are left alone,
the later mod obviously just shooting for better program memory space.

Funny construction. This thing should have been able to go through a
single wave solder, with it's smd parts adhered to the underside. The
only orphan in the process, now, is the PIC, which has to have been
placed and soldered manually to the under side, post-wave. No plated
through holes, but a pretty good supply of autotest points on the
solder side, so not everything is left to luck in production.

The reason for the cracked board is finally suggested to be a
piece of 1/8th long wire insulation that has been stripped
off a wire, then jammed sideways between the negative and signal
terminals - preventing total battery insertion and possibly
pushing the battery back out of contact when insertion pressure
was removed. This was the same colour as the housing and could
easily have been mistaken for an intentional physical detail of
the assembly.

Sort of a warning to all designers - the product recall of this model
number in ~Y2K was also about the connectors - they were detatching
and rattling around 'presenting a potential shock hazard' when lodging
in the air holes. There's no internal isolation barrier present, just
the plastic of the charger frame and battery housing providing
reinforced isolation. Makes sense if you're going to pay 'all that
money' for the tooling and material anyways, just for a charger.

Anyways, connectors need care.

RL