my computer will not turn on at all. i was told it could be a bad power supply and just wanted to now how to tell if my power is bad. also, i also ahve 256MB RDRAM PC800 Memory and would like some info on upgrading to 512mb. what type of ram do i need, does it have to be RDR pc800? thanks alot

See that all cables and conections are not loose, if still won;t work, then it's a bad PSU. For the RAM, stick with the type you have.

The real backyard approach would be to listen for the fan to spin up. A better approach would be to use a voltmeter and check the power at the connection to the motherboard. Typical voltages might include: Red = +5V Yellow = +12V Blue = -12V Orange = +3.3V Purple = +5V Check the power supply for these values, as I don't want to unintentionaly mislead you.

Voltage without amperage is useless.Same as some curcits have no resestince untill you put them under a load and then you have voltage drop. But if you have no voltage at all on those wires then the PSU is definatly bad .But if you have voltage that does not nessacarily mean your PSU is good . Back probe your fan or cd rom or hard drive and then see if you have voltage. Try backprobing the red wire at the atx connecter with it hooked up and turned on and use the blackwire for ground with a DVOM not analog if you use analog meter you may fry something

Perhaps I should have said to leave the power supply hooked up to everything while you are taking voltage measurements, this will add validity to your measurements. Inside your power supply you will most likely find that all the leads of any given voltage are connected to the same point. Therefore there is no real advantage to measuring here and there. If you don't, for instance, have 5V at the motherboard connector, you are not going to have it at the CDROM either. Measure where it is most convenient, but since the motherboard connector has all the different voltage levels (as a general rule) it becomes the prime target. It really doesn't matter if you use analog or digital test equipment, not if you confine your probing to the power supply leads. Most VOM's have an ohms/volt rating at the bottom of the face of the meter. Here is the math for my cheapy Micronta; 2k ohm/V This means if you have the scale set to 15V, then the internal resistance would equal 30k ohms. If you were testing a 12V power supply source this resistance is paralled with whatever else is hooked up. You can add the conductances for these ciruits (meaning adding the reciprocals of the individual resistances) and determine the current draw of the entire circuitry....or just take the easy method and divide the 12V by the 30k ohms..... which would equal 400 microamps. That value is so small, that if it should load your power supply down enough to drop the voltage then you would know that your power supply truly is no good.

Art Smass,You are correct again.I am an auto tech and do a lot of electrical work and you never use a analog meter when checking programed fuel injection or multiplexers period.I just assummed that this would also apply to PCs. But since it is the power supply he is testing it would not really matter if he did use an anolog meter Much like testing the 12 volt car battery Take Care Ron Watts

Ron, Auto tech...cool!! I've worked with a few of them, and always I learn something usefull. I hated those OBD1 code readers, but finally learned how to use them (for a couple of different vehicles anyway). I bought an OBD2 reader some time ago (just for personal use on the family cars). It is so much more user freindly I think.