11-24-2010 05:42 PM
It was working fine last night... I woke up to a computer turned off. I try and hit the power button, nothing happens! The LED in the back is lit solid green though. Fans arent even working! Any Idea what the problem could be? It is no longer under warranty and HP is quiet pricey . I know its either my motherboard or my power supply.. How can i tell which one it is?
11-24-2010 05:45 PM
Try this procedure and see if you can isolate the issue. Trouble Shooting Power Supply Issues. Don’t skip any steps.
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11-25-2010 02:32 PM - edited 11-25-2010 02:33 PM
tried it all.. doesn't turn on. the led remains solid. i'm guessing its my mobo thats dead?
where can i purchase a new motherboard for this desktop? besides hp. the price is ridiciously expensive. this pc isnt even 3 years old yet.
11-26-2010 09:45 AM
Unplug mouse, keyboard, monitor, and all other external hardware cables.
Plug in only power cord. The PSU light should be green
1) press the power button, the fans should spin very briefly, sometimes just a flicker.
2) Then the PSU light goes out.
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11-26-2011 11:53 PM
I just happen to also be working on a friend's m8530f with the same symptoms. He already tried replacing the PSU (power supply) and the system still didn't power up, so he asked me to take a look. I first tested the original power supply using a simple power supply tester (one with a display) and all voltage lines looked OK (except -12v, which almost no power supply does right these days). I then bench tested it with a different CPU and motherboard and it worked fine under load (IntelBurnTest). Since the PSU checked out, I re-installed it back in the system with just the motherboard connected, every other cable disconnected, and shorted the power-on jumper - *very* brief fan spin, then dead. This usually points to a motherboard problem...
So, I removed the motherboard, did some looking (and sniffing) around, and low-and-behold, a very common problem was discovered - a bulging capacitor. Bad caps are probably the most common cause of electronics failures these days - unfortunately more so since the industrial espionage fiasco gone wrong about 10 years ago (employee took secret electrolyte formula with him to a new employer and they manufactured millions of caps before realizing that the formula was missing the stabilizer). A year or so later, many motherboards, power supplies, monitors, TV's, cell phones, etc. were starting to die en-mass. The cause was eventually traced back to the bad caps, but millions of these caps were/are still in existence in products and many are still being sold cheap as old stock to un-wary customers.
Anyways, please refer to this reference for the m8530f's motherboard:
The power conversion circuitry (DC to DC) is at the top left of the motherboard between the CPU socket and the I/O panel. If you look just to the right of the video port, there is a brown electrolytic capacitor between two silver caps with red polarity marks (stripes). On the motherboard I'm working on, this cap has bulged and split open on top with brown corrosion caused by the electrolyte (the "Y" serrations on the tops of the cap are actually there to help the cap bulge/burst in case of catastrophic failure - and they can pop like a firecracker!).
Check your motherboard and see if any of the caps are bad - the ones in the DC-DC circuit are under the most amount of stress and usually go bad first. Do a google search on "bulging caps" for more references and photos on what to look for. If you find any bad caps, you have a few options:
1. Replace the bad caps - cheap if you can do it yourself and makes life easy as you don't need to re-install the operating system because the motherboard is the same. But, make sure you use appropriate caps (e.g.. low-ESR, if necessary). Also, when caps fail, they can cause an electrical short-circuit, so even if you replace the cap, another in-circuit component (usually a power transistor) might also need to be replaced.
2. Hopefully, the CPU is still fine, so find a replacement motherboard. Just make sure the new motherboard works with the existing CPU and RAM - otherwise, you'll need to replace those too. Today, I just picked-up an MSI K9N6PGM2-V2 to replace the original MB. Haven't had a chance to install it yet (tomorrow), but it should work with the existing CPU & RAM. Be aware that DDR2 based motherboards for AMD CPU's are getting harder to find. Depending on the motherboard, you might need to re-install the operating system as the MB might use a different chipset (I expect to need to do this with the K9N6PGM2). You may also need to call Microsoft to re-activate Windows as this is major hardware change.
3. Buy a new computer.
Sorry for the long-winded post, but wanted to be thorough in my explanation. Check the caps and see if that's the problem.
11-27-2011 08:30 AM
Similar problem with my Pavilion 751n (Pentium 4). In my case, with everything external disconnected, the power supply light will go on when the power cord is plugged in. As soon as I press the power switch, the power supply light goes out. No movement of any fans. Unplugging and replugging the power cord will turn the power supply light back on. I tried disconnecting every power supply connection inside the computer, and then when I press the power switch, the power supply light stays on. One by one, I reconnected the power supply connections, and the one that causes the problem when connected is the large (20 position) connector to the mother board. I cannot see any signs of damaged caps, and the inside of the computer is really clean (no dust). I suspect that there is some kind of circuit breaker inside the PSU that kicks out when the power supply button is pushed, and that there is some kind of short on the mother board. That acts like a blown cap, but I can't see any with physical damage. Anyone with insight, thanks in advance!
12-12-2011 05:55 PM
To Jeepster...though similar in symptoms, it's usually best to start a new thread if the hardware is different as specific models may have a known problem/solution - you can always link to another thread (such as this one) for background info or similar situations. That said...
The PSU and MB "talk" to each other during power-up. In actuality, the PSU is always supplying +5v to the MB and the MB uses that +5v to for mundane things such as detecting if the power switch is pressed, listening/waiting for a "wake-up" event (e.g. wake-on-lan or a timer event), keeping the RAM powered during "sleep", etc. If the system is fully off and the power button is pressed, the MB does a quick test to make sure nothing's "wrong", then sends a signal (Power Good) back to the PSU. If the PSU doesn't receive the PG signal within a specified time frame, it assumes the MB is not connected or the MB is experiencing a problem and cuts power. That's why you see a system power-up for a split second and then shut-down when a problem exists.
As for bad caps, they don't always blow the top off. Sometimes, the bottom of the cap blows out and you might see the rubber seal popping out (and often electrolyte leaking out).
So, for your situation, if everything is disconnected from the MB (except the main power and CPU power plugs) and the system doesn't power-up when you push the power button (or short the PWR-ON pins), then something is probably wrong with the MB, CPU, or PSU (regardless if it's bad caps or not). Best way to confirm is to "bench test" the MB (MB/CPU out of the case) with a known good PSU - if it still doesn't power up, then MB or CPU is at fault and proceed accordingly.
***** Update to my previous post *****
And, for reference, the MSI K9N6PGM2-V2 worked fine with the old CPU, RAM and PSU. I did have to re-install Windows 7 (as expected due to different chipset), but the original Windows 7 key on the MS authenticity label worked just fine over the 'net and no call to MS was needed (YMMV). Word of warning...this MB has fewer SATA ports, no IEEE1394 (Firewire), and won't do Hybrid-SLI, so it's not an exact replacement for the original MB. But it is cheaper and easier to find. Other uATX motherboards should also work fine.