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ArtemusComputerTechnology
02-03-2012, 08:40 PM
Earlier this week, a customer bought in an HP Pavilion 7935 desktop running XP and only 512 MB of RAM. She advised me of a power problem. Her machine is not charging and booting up. I checked out the desktop, ran a test with my PSU tester. The PSU was burnt out. So I ordered a new PSU (the exact same) from Amazon with free two day shipping. Thanks Amazon Prime. I swap the PSU, the computer will not boot. Big problem. I am truly lost here.

phaZed
02-03-2012, 08:49 PM
PSU's are known to take out other components on their way out. Also, lighting and surges/brownouts, etc.. are not limited to affecting the power supply only.

Have you tried the NEW PSU in a different computer? Make sure it's not DOA.

Now may be a good time to consider keeping a known good PSU on hand so that you can test with it. PSU testers only go but so far... I have an Antec tester with the screen and it has misdiagnosed PSU's for me before. It kind of plays like a broken record here on TN, but just because the voltage is there, doesn't mean that the PSU can deliver under load. PSU testers don't work the PSU under load....

anonymous Mac Tech
02-03-2012, 08:54 PM
I swap the PSU, the computer will not boot. Big problem. I am truly lost here.

Not boot or not power on?

Lost? If this perplexes you this bad this is going to be a tough profession.

OldSchoolPC
02-03-2012, 11:13 PM
Not boot or not power on?

Lost? If this perplexes you this bad this is going to be a tough profession.

I am afraid that I must agree with the quote above. But it's ok, not all hope is lost. Just spend more time on the forums. In particular, read power-related threads.

P.S. One rule of thumb is to diagnose twice, order parts once.

red12049
02-03-2012, 11:48 PM
Earlier this week, a customer bought in an HP Pavilion 7935 desktop running XP and only 512 MB of RAM. She advised me of a power problem. Her machine is not charging and booting up. I checked out the desktop, ran a test with my PSU tester. The PSU was burnt out. So I ordered a new PSU (the exact same) from Amazon with free two day shipping. Thanks Amazon Prime. I swap the PSU, the computer will not boot. Big problem. I am truly lost here.

Not charging? Charging what?

Rick

mil0001
02-04-2012, 01:38 AM
Take out all the PCI cards etc, disk drive, ram and see if it can at least boot. If it does then its probably one of those componenents failing.

If you've tried the new PSU in another computer and it works then I would look into seeing if the motherboard has any bulging capacitors/brown spots etc.

glricht
02-04-2012, 02:44 AM
Not charging? Charging what?

Rick

Was wondering the same thing myself. Exactly what, on a desktop, is not "charging"?

d3v
02-04-2012, 03:11 PM
it could very likely be a bad mobo, but could also be as likely a bad stick of RAM, so try with some good RAM first! If it still dosn't start up with good known RAM then it's the mobo that needs replacing.

sys-eng
02-04-2012, 03:56 PM
A customer hired me to backup her data before she sent the SysteMax desktop off for motherboard replacement. She purchased a 3-year extended warranty with her PC. She could not perform the backup because the PC would not turn on. The "support technician" had told her on the phone to remove the side panel and see if the green light is displayed on the motherboard. If it is, then the PSU is OK and the motherboard is broke.

Hmmm. I get PC to my shop, connect it up, and turn it on. It boots right into Windows with no problem so I make backup DVD's on her own DVD drive. I test the PC by restarting it until it fails after about 10 restarts - actually shutdowns and manually turn on.

I do not know how to surely tell if a motherboard or PSU is bad over the phone so I test it out myself.

Connect my PSU tester and the PSU fires right up like it is suppose to do.

Reconnect the PSU to motherboard and the PC turns on.

After several more shutdowns, the PC would not turn on.

Shorted motherboard pins to power switch but nothing happens.


Connect spare PSU and PC turns on fine.


Shutdown PC and manually turn on about 20 times and works fine every time.


Contact customer and she tells the customer what the problem really is. Now, she does not trust the technicians doing the warranty work so she tells me to replace the PSU at my price and she will not have to pay shipping costs and be without PC for weeks. I point out to her that she has both AVG and MSE installed and one of them should be removed. She tells me to fix that problem too.


I fix PC and return to customer the next day. I make money and get a new impressed customer.



PS: I did forget to check if it was charging or not. Must add that to my quality checklist.