[Mobile-Portable] Re: Unknown power supply

[Art Clemons]

> I've been given an inoperative regulated power supply (120 vac to 13.8 dc) with a generic circuit schematic that doesn't seem to represent what is actually in the supply. The only identification marks on the unit are (a) the capital letters "ER" (stylized, the E consisting the three horizontal bars only, followed by the R, and both letters leaning/slanted to the right), and (b) the apparent model number PS-109. It states that it is rated at 13.8 volts (fixed), amperage at 30-32.

Most transformer type power supplies only have a limited number of
things that are likely to go wrong, with the most likely suspects, the
transformer, the rectifier assembly and of course the pass transistors.
 I haven't bothered to look at a schematic until after identification of
the failed part(s) has occurred.  It's only then that knowing just what
part needs to be replaced.

I would personally start out looking for voltage from the transformer
leads (likely somewhere around 24 volts or so), it that's present, then
I would look at output from the rectifier/diode setup for DC voltage,
then for DC at the capacitors, after that voltage at the input to the
pass transistors.  Where the voltage disappears is where the problem is.

Oh yes, I almost forgot, check the 120 volt input too, the fuse could
have blown or the power cord could be faulty too if there is no voltage
at the transformer.