Jackietools

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My father in-laws old Gateway 500s was working fine when suddenly he went to turn it on and all he gets is black screen. I put his monitor on another PC and it is fine. I hear the fans turning but get no CMOS beep and no bios, just black screen. I put new Ram in but that was 2 years ago. I am going to switch the RAM and check it tomorrow but are there are any other ideas. It has onboard graphics, could that be the cause. The PC is 10 years old. I dont have a discrete GPU to try as I think it only AGP and am not about to get one to check my theory. Im open to ideas or troubleshooting tips. Yes I know it is a piece of garbage but it is really fine for him to go on the web. Thanks.
 
Solution
There are only two ways to test a PSU, and since you've got a multimeter, I recommend you use the multimeter test. The other test, a far less accurate method, is simply jumping the green wire with a neighboring black wire. This test can provide false positives, in that if the PSU turns on, some believe this to be an indication of proper operation.

Using the multimeter, touch the black lead against any black wire, or bare metal on the case. Touch the red lead to the following wires, and verify their voltages, while the computer is powered on:

Red = +5V
Yellow = +12V
Orange = +3.3V
Blue = -12V
Green = +5V
Purple = +5V
Brown = +3.3V
Gray should go from 0 to +5V when you turn on the case switch

Jackietools

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Would the fans still turn if it was the PSu. I think I have an old dell 300W PSU from a 5150 I could try. It's worth a shot.Thanks. I also have a multimeter, any suggestions on sites to guide on the proper way to diagnose a PSU
 

HugoStiglitz

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easiest way to diagnose it to take a PSU from a know working PC (hopefully its around the same watt rating as ur suspect PSU) and plug it into your dead PC.

if you get the same issue as before, its prob not ur PSU but ur motherboard (bad news im affraid)
 
There are only two ways to test a PSU, and since you've got a multimeter, I recommend you use the multimeter test. The other test, a far less accurate method, is simply jumping the green wire with a neighboring black wire. This test can provide false positives, in that if the PSU turns on, some believe this to be an indication of proper operation.

Using the multimeter, touch the black lead against any black wire, or bare metal on the case. Touch the red lead to the following wires, and verify their voltages, while the computer is powered on:

Red = +5V
Yellow = +12V
Orange = +3.3V
Blue = -12V
Green = +5V
Purple = +5V
Brown = +3.3V
Gray should go from 0 to +5V when you turn on the case switch
 
Solution

Jackietools

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I think this is the way to go. Although the other suggestion of swapping out PSU isn't bad I think Ill use the multimeter to be sure. I hope the MOBO is dead so I have an excuse to build him a new PC and stop having to troubleshoot these old relics but as a builder of Pc's myself I still want to know what exactly the problem is. Thanks.
 

Jackietools

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Thanks. No matter what it is I will strongly recommend that he does not put any money into this PC