Another dead power supply

[phiscock-g851W1bGYuGnS0EtXVNi6w at public.gmane.org]

For the second time in as many years, a power supply in one of my
computers has died.

The previous power supply death took out every item in the box with it.

This time, there was some sort of over-protection device that prevented
the power supply from damaging anything. Apparently some power supplies
have a zener diode across the output that clamps the output voltage to
about 5.1 volts. When the output voltage attempts to rise, the zener
conducts and gets hot. This is sensed by some sort of temperature sensor,
which then shuts down the supply.

Both these power supply failures were white box units from OTA on College
Street. The first one they eventually gave me something of a deal to
replace the contents of the box, but only after some serious arguing. (The
OTA manager argued that the failure occurred because I didn't have a surge
protector on that circuit, which is nonsense. I've designed switching
power supplies, so I'm aware of the importance of output protection, and
that supply obviously didn't have it.)

The moral: buy a good power supply, and make sure it has some sort of
protection circuit on the output.

Peter
-- 
Peter Hiscocks
Professor Emeritus,
Electrical and Computer Engineering,
Ryerson University
416-465-3007
www.ee.ryerson.ca/~phiscock

--
The Toronto Linux Users Group.      Meetings: http://tlug.ss.org
TLUG requests: Linux topics, No HTML, wrap text below 80 columns
How to UNSUBSCRIBE: http://tlug.ss.org/subscribe.shtml