power supply

[jinxy]

Hey, anyone out there know of a good site with some visual aids on how
to bench test a power supply? If so please send a link. Thanks
-J

 

[n0ctis]

As far as bench testing is concerned, no; but Computer Power User last month
(computerpoweruser.com) ran a pair of articles on PSUs, the first being a
rundown of PSUs themselves and what to look for, and the second being a review
of some newer high end PSUs.

 

[w_tom]

Hey, anyone out there know of a good site with some visual aids on how
to bench test apower supply?

You have an oscilloscope, and what kind of loads? Static?
Dynamic? Reactive? Otherwise learn why the best computer testing is
the power supply inside the computer - no wires disconnected - and a
3.5 digit multimeter. A tool so ubiquitous as to be sold in Lowes, K-
mart, Radio Shack, Wal-Mart, Sears, Home Depot, other hardware
stores, .... A tool as importathings before failure occurs.nt as a
screw driver when doing computer work IF the objective is to fix

 

[jinxy]

You have an oscilloscope, and what kind of loads? Static?
Dynamic? Reactive? Otherwise learn why the best computer testing is
the power supply inside the computer - no wires disconnected - and a
3.5 digit multimeter. A tool so ubiquitous as to be sold in Lowes, K-
mart, Radio Shack, Wal-Mart, Sears, Home Depot, other hardware
stores, .... A tool as importathings before failure occurs.nt as a
screw driver when doing computer work IF the objective is to fix

Alas , the objective is not to FIX, but determine if the ubiquitous
power supply which is sold at tiger direct, new egg, and many other pc
suppliers has failed. And if a screwdriver is needed, then a
screwdriver it be! Sarcasm,yes thats the answer.
-J

 

[Paul]

Hey, anyone out there know of a good site with some visual aids on how
to bench test a power supply? If so please send a link. Thanks
-J

This company makes automatic test equipment. The list on the bottom
of the page, gives some idea of the tests that can be run on a power
supply.

http://www.chromausa.com/apsts2.htm

This unit looks more like a load box, and this one can be programmed
for specific load values. You would read the ratings off the label
on the supply, then program so many amps load per rail. Then see
if the unit overheats and shuts off, see whether it maintains its
output voltage, perhaps check Vpp AC noise and ripple on each rail
(should be less than some number like 100 or 150 millivolts).

http://www.sunmoontec.com/cpzs.asp (SM8800 tester)

So what tests can you reasonably expect to do in a home or
small business environment, with a limited budget ? Basically,
that would be voltage regulation, and monitoring for correct
operation (fan fail, sparks, smoke, clicking, power cycling).

You can build a static fixed load, using power resistors from
an electronics store. Some surplus places offer good deals on
old power resistors. You need a basic understanding of
Ohms law, the combination or resistors in series and parallel
to get different values, how to work out the power dissipated
in a resistor, to successfully build your own load. I've built
a simple load which I used to test a few supplies, and it is set
up for a pretty small load. The power resistors I use, are mounted
next to an 80mm fan, so I can keep the resistor temperature down
while the load is being used. It might cost $50 to make a
setup like that. Then, you need a multimeter, to verify the
voltage being delivered, is constant and correct for the couple
hours you might run the supply. You can spend a fair amount to
get a decent multimeter. Mine isn't that good and cost about $100
(I purchased it well before building the load box).

In this posting, I give examples of resistor values suitable to
model an old AthlonXP motherboard, and for a P4 Northwood motherboard.

http://groups.google.ca/group/alt.comp.periphs.mainboard.asus/msg/19647caf2c65504b?dmode=source

This is a fancy Tomshardware version of a load box:

http://www.tomshardware.com/2005/07/11/stress_test/page5.html

This is a Tomshardware "ghetto" tester (still nicely constructed).
Load is programmable by plugging in jumper strips.
This might be good enough for a mom & pop computer store.

http://www.tomshardware.com/2002/10/21/inadequate_and_deceptive_product_labeling/page4.html

HTH,
Paul

 

[w_tom]

Alas , the objective is not to FIX, but determine if the ubiquitous
power supply which is sold at tiger direct, new egg, and many other pc
suppliers has failed.

As Paul demonstrates, do you have all that equipment? Do you have an
oscilloscope? If not, then a best alternative is to connect a power
supply to your best bench tester - a computer. Maximize the load
(multitask to all peripherals). Then read voltages with the
multimeter. Resulting numbers report supply either as good or
insufficient. Numbers may also demonstrate some supplies with
superior regulation.

Any analysis of a power supply means numbers; as Paul's post also
demonstrates. Do you have an oscilloscope, massive programmable
loads, and other test equipment? If not, your best alternative is
using a computer as load to get numbers from a 3.5 digit multimeter.