[EMAIL PROTECTED] wrote:
Subject: Subject: Re: PB 160 - appears dead
Electronics is my hobby and power supplies are my "thing".
In general I don't open up those "wall warts". I have about
150 of them I've collected over the years, and can usually find
one that matches my needs in this pile of tangled wires and plugs.
But sometimes I can't, and it's time to pry the offender open
and inspect the guts.
I believe you have isolated your problem. Realize that the
output from that plug will be somewhat higher than 7.5 volts
when you check it with a voltmeter while it's not under load.
When it's loaded (plugged into the computer, computer
operating) the measured output voltage could be about
9 volts. If it's as much as 10 volts I'd be concerned.
With some "wall warts" the components inside are "potted".
This means the components are imbedded in epoxy or
another polymer. This also means that getting to the individual
components is impossible. In extreme cases I have used a
hacksaw to (carefully!!) cut the "box" away from the plate that
has the plugs that go into the wall. Very carefully!! Sometimes
a well-placed screwdriver will do the job. I would not start
whacking away at it until totally convinced that there's a good
reason to look inside.
In high-quality power supplies there is a voltage control
regulator... either a fairly large zener diode or a regulator
"chip" that controls the output voltage. If it's not potted, then
maythe zener diode may be easy to replace. In the best of
worlds the zener diode has a number on it that can be
"looked up" to learn (1) it's voltage and (2) its wattage.
Replacing a voltage control regulator "chip" requires a
lot of tender loving care. If you do open it, look for parts
that seem to have been overheated. If you work with
electronics, the trick is to "load" it with a high-wattage
resistor across the output and check for parts that are
getting too hot. Then check voltages at appropriate
points, etc.
I wonder whether the adapter you are using is putting out
a good, solid 7.5 volts when it's "loaded"?
From: Charlie H.
Charlie, I just realized that my response yesterday was in error. When I
switched the meter range from 10 to 50 volts, the reading was in the low
end of the 50 range so you're right, it probably is sending out
something more than 10 but not really high when the PS isn't under a load.
The connecting pin seems very loose on the pin coming from the laptop so
maybe there isn't sufficient contact to power up. I think this should be
intermittent however instead of always dead.
Thanks for the responses, I'll post again if I ever figure out what the
problem is.
BM
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