February 7, 2024 email:
Commenting on Those Darn Wall-Wart Power
Supplies! A few years ago, I had a friend store his
motorcycle at my house, with a wall wart battery
trickle charger. Eventually I forgot about the
charger. Eventually I noticed a beeping sound coming
from my AM radio. It was like Telstar, beeping away
not just on BC, but also on Shortwave. All over the
dial! So I disconnected anything in the house that
might be interfering, took a portable radio and
walked around the house. Didn’t find anything
inside, so I tried outside, and sure enough, at the
power box, the beeping grew louder. So I went to the
front yard power pole. Beeping increased again, so I
concluded (erroneously) that it was a neighbor.
Weeks go by. I finally get mad enough to check one
more time with a portable. This time it dawns on me:
I never pulled the battery charger wall-wart. So I
did, and the beeping immediately stops. I looked at
the wall-wart to see if this was some sort of cheap
imported thing, and what do I see, but a logo from
the Canadian version of our FCC, assuring me that
the device will not interfere with radios! Ever
since then, I hate switching supplies.
Duke Evans, WBBF-FM Radio in Buffalo, New York.
February 5, 2024 email: I
totally agree with Mark Persons. The old-fashioned
transformer / rectifier / filter capacitor wall-wart
power supplies failed mostly because the
electrolytic capacitor dried up and the output had
as much ripple as DC. But those are getting harder
to find as modern wall-wart supplies are switching
supplies. These are less expensive, smaller,
lighter, and more efficient. In some areas like
California they are required because of the higher
efficiency. These suffer from the same problem:
limited lifetime of electrolytic capacitors. There
are wall-wart supplies that are just a transformer
and provide an AC output. These are much more
reliable because the rectifier and filter are
located in the equipment and operate much cooler.
Besides life they have been known to fall out of the
power receptacle, especially when vertical. And they
tend to take over power strips unless you have short
Edison cables to spread them out away from the
closely spaced receptacles on power strips. I can go
on and on over my dislike of wall-warts with many
war stories about their failures and problems caused
to stations. Yes they are inexpensive and
convenient but when providing DC power to part of
your air chain I strongly recommend getting an OEM
style open frame linear supply and taking the time
to mount that to a rack panel with a fuse and other
accessories. Bill Ruck, San Francisco.
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