Help!!

[mixedgas]

Sadly, the last sentence here is not true. Many PC power supplies are unstable, poorly regulated, or just plain don't start without a load on the 5v rail. See Horowitz & Hill for the reasons why.

Yes, and many PC power supplies are poorly regulated. And on many I've worked with you need 1.5 to 2 ohms on the 5V to even get them to regulate. If not loaded, many of them relentlessly pulse, looking for a load.

Steve

[SideFX]

Sadly, the last sentence here is not true. Many PC power supplies are unstable, poorly regulated, or just plain don't start without a load on the 5v rail.

Ok.. after doing some searching (eg. http://www.pcguide.com/ref/power/sup...Loading-c.html)
i learned i shouldn't have stated that as a fact.

However the PSU's I've been using started nicely without load, and showed a nice +5V with just a DMM.. so maybe i just got lucky

See Horowitz & Hill for the reasons why.

You mean 'the art of electronics'? sounds like an interesting reading.. never heard of it before..

[heroic]

Ok.. after doing some searching (eg. http://www.pcguide.com/ref/power/sup...Loading-c.html)
i learned i shouldn't have stated that as a fact.

However the PSU's I've been using started nicely without load, and showed a nice +5V with just a DMM.. so maybe i just got lucky

You mean 'the art of electronics'? sounds like an interesting reading.. never heard of it before..

DMMs lie when voltages are changing. Best to use a scope- you can get a cheap (old, or small) scope for less than $100 these days. If you're going to do much electronics, you'll wonder how you ever survived without one!

The Art of Electronics is a truly awesome book. Everyone who works with electronic circuits should read it.