reverse-engineering power

From: Doug Yowza <>
Date: Sat May 16 20:10:58 1998

> > Describe what the plug looks like (number/configuration of
> > the pins), first of all.
> Great minds think alike :-). That's my first question as well. 2 connections
> implies an internal regulator, a lot of pins probably means it wants
> 'standard computer-like' voltages.

OK, Great Minds, there are two pins in the standard center/outer config
associated with most wall warts.

> > If there's any way to open the box up, look for any obvious rectifiers and
> Are the computers you can't open up?

There are few computers easier to open up than this one. Refer to figure

> > tantalum/elecrolytic capacitors near where the power comes in. This'll give
> > a good indication of the polarity and a rough guess at the voltages.
> Also, are there any transformers/large inductors in the PSU, implying a
> switching-type regulator ? Any power devices or chips with sane numbers?
> You might be able to deduce a lot from that.

There seems to be a transformer that helps out with the display voltage,
but it's the only thing in the box that's hard to get to. I can tell it's
on a PCB labeled P/N 665-0454 (just in case it matches one sitting by

Here's where software-boy gets in trouble. There's a part near the DC-in
that looks like it by be a transistor. The board label is D3 and the part
is labeled 1R OE 30WQ0AF (maybe). The center conductor buzzes on the
outer two pins of this three-pin device. Also nearby is a 16V 470uF cap,
but it's not easy to trace the connections. The center conductor buzzes
with what I think is the negative terminal of a tantalum cap on the
trace-side of the board.

Are those clues enough to nail down the polarity?

-- Doug
Received on Sat May 16 1998 - 20:10:58 BST

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