A quick look under almost
any computer workstation and you will usually find a half dozen different power
adapters. External computer hard drives, laptop computers, computer speakers,
cell phone chargers, radios, MP3 player chargers, USB hubs, printers and cordless
telephones all use power adapters. The trend lately has been to use a solid state
switch mode method to convert the AC to DC. This method makes for a compact and
light weight assembly. But, the more complex electronic circuit inside these little
black boxes is not as robust as the older power supplies, which relied on a small
transformer to make the voltage conversion. In most cases, at least based on my
own troubleshooting experiences, the failures tend to center on defective electrolytic
filter capacitors.
This puzzles me. The
electrolytic capacitor technology has been around for a long time and their
manufacturing should have long ago matured. There is no reason why such devices should
fail so quickly. I have many old complex electronic devices filled with these
kind of parts and they are still working fine. I have one old HP calculator,
which is powered by a wall adapter, and the thing is at least 35 years old. I also
have an old power supply which must be over 40 years old and it still works fine.
What has changed? Clearly the one common factor among all the wall adapters
which are failing is that they are being made in China. Why can’t they build
devices which last longer than a few months? |