Earlier we shared a letter from Duke Evans responding to an article by Mark Persons about wall warts. Here are two more on that subject from readers.
Warts
I totally agree with Mark Persons in his article “Those Darn Wall-Wart Power Supplies!” in the Feb. 1 issue.
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 efficiency. But they suffer from the same problem: limited lifetime of electrolytic capacitors.
There are wall-wart supplies that are simply a transformer, providing an AC output. These are much more reliable because the rectifier and filter are in the equipment and operate much cooler. But they have been known to fall out of the power receptacle, especially when vertical. And they tend to take over your power strips unless you have short Edison cables to spread them out over the closely spaced receptacles.
I can go on about my dislike of wall-warts and my war stories about their failures and the problems they 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
And More Warts
Mark Persons mentioned that repairing switching power supplies is beyond the ability of most techs. I’ll say from my own experience that most of these failures are also caused by capacitors, so I feel that should at least be investigated.
I sympathize with the author about the noise floor on the AM band. Unfortunately, there are so many devices now that cause this. I have gone through my own home and made it friendly for AM broadcast reception by eliminating most switching PSUs — using linear ones — filtering others and installing certain types of LED light bulbs that are not switching (they do exist). I’m a vintage radio collector so this matters to me.
— Bruce Girard
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