Computer powers on but no POST

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jvnderwe

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So this morning I attempted to turn on my computer and it will not boot. All the fans turn on but I get no signal to the monitor and no beeps. The keyboard lights up for a second and the DVD drive opens and closes. I tried removing all but one stick of RAM, and moved the one stick around to different slots but with the same result. I also tried booting the computer without any RAM at all and I didn't hear any beeps. Does this guarantee that the problem is the motherboard?

I have an Asus P5B-VM, Intel Q6600, 8800GTS 320MB, 4GB RAM, Antec Sonata 3 case w/Earthwatts PSU.
 

crjdriver

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No, it does not. It may in fact have a failed board however the very first thing to test is to swap in a known good pw supply. Note known good does not mean new; it means one pulled from a working system that you know works.

Post back with results and we can continue troubleshooting if needed.
 
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If you are using the 500 watt Antec Earthwatts you show in your computer specs, it is not enough for a quad core processor with a 8800 series graphics card.
 

jvnderwe

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That's strange, I think I have had this computer for 4 years now and the power supply has not been a problem even when doing pretty intensive tasks like gaming and video editing. I'll have to see if I can get my hands on a working power supply to test with as I don't have one on hand.
 
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You may very well have "stressed" the power supply during that time and now have a rail dropping out. I built two machines almost identical to your configuration back in 2007 or 2008 for 2 kids and used Corsair 650 watt power supplys.

Ideally, with a high powered processor and graphics card you should not go above 75% of it's rated output for problem free computing and longevity.
 

jvnderwe

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Ok, since I don't have access to a known working psu I think I will take my computer to my local computer shop and see if they can test the psu for me. I'd prefer it if the psu is gone as opposed to the motherboard, it would be easier to fix and they have a good sale on a 650 watt antec psu right now. Thanks for the help.
 

jvnderwe

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Update:

So I took the computer into the shop to have a diagnostic done. The first thing the guy did was plug in a different PSU and test it, but it still did the same thing. He tested a couple other obvious things but couldn't figure it out, so he said he'd try testing each component individually, but I'd have to wait a while. So after a couple days he phones me and says he tested every component and determined that it must be the motherboard because every other component works fine when put into a different system. So I call a bunch of places and finally find someone who has an LGA775 motherboard in stock that takes DDR2 RAM. I get it home and put it all together (after taking another trip to the computer store for a new heatsink as I broke a damn plastic clip taking it out of the old motherboard), and the EXACT SAME THING HAPPENS.

So what the heck?! I saw him test a different PSU so unless the one he used also happened to be broken it can't be that. I already tested the RAM and GPU, and he insists that the CPU worked in another system. Could something in my apartment be breaking my computer? Bad power outlet? Bad power bar? I just moved into this apartment 2 months ago.

This computer is 4 years old so I don't want to spend anymore money on it and I think I'll just buy a new computer in January when I get some money from a work benefit program that can be used for computer hardware. However, now I'm worried that there is some other factor here that could potentially damage a new computer as well, is this possible?
 
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What is the exact make, model and revision of the new motherboard you purchased?

When the shop had the machine other than jumping a known good power supply to the board did he or she test the old power supply with a power supply tester? If the technician did test the old power supply with a power supply tester, did he or she write down and record the output voltages on the +3.3v, +5v and +12v rails and the response time of the power good signal? If the technician did record the values of the +3.3v, +5v, +12v rails and the response time of the power good signal what were they?
 

jvnderwe

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The new motherboard is an Asus P5G41-M SI.

When I first went to the shop the tech did a quick test while I waited, which involved swapping the power supply. When that didn't work I left my computer there and he phoned me back a couple days later, so I don't know exactly what other tests he did, but he didn't mention anything about testing voltages on the PSU.

Perhaps the PSU was the root of the problem all along and the reason using a different PSU didn't work is because the bad PSU had fried the motherboard? Can that happen? Of course, that would probably mean that the new motherboard I just bought would be fried now too.
 
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I went to the Asus site to check the attributes of the board you stated you purchased, i.e. Asus P5G41-M SI and am unable to locate that particular board at the Asus site. I can find a P5G41-M, P5G41-M LE, P5G41-M LX but no P5G41-M SI.

I also looked at the specs on 3 or 4 other Asus boards that used the 41 series chipset and although all I looked at including the ones above supported the Q6600 with G0 stepping, but I did not see any that indicated they supported the Q6600 with B3 stepping.

We first need to determine which processor you have. The Q6600 was first released with B3 stepping and the sSpec # for that processor was SL9UM. The sSpec # for the Q6600 with G0 stepping was SLACR. When you initially got the machine did you record the sSpec # of your processor?
 
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When I get a machine in with problems that may be power supply related the first thing I do is test it with a power supply tester so I can see if the output voltages and power good signal are within tolerances. Even if the output voltages and power good signal are within tolerances I next "jump" my known good workbench power supply to the board to verify that the power supply is not the problem.

On my initial test, if the power supply voltages are low or power good signal is high and is not within tolerances then I would "jump" my known good power supply to the board to see if that solves the problem.

If the power supply voltages are high, of course I would not connect it to another new or known good board.

If the technician who checked your machine did not check the output voltages of the old power supply, in my opinion he or she did not do a proper job of troubleshooting.
 

jvnderwe

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I no longer have the box for my Q6600 so I'm not sure which model it is. I checked the manual for the new mobo and it doesn't list exactly which processors are supported, it just says "Core 2 Quad". However, it says that if you use and unsupported CPU then the system will display an error message and shutdown - my computer displays nothing.

So it seems like the best guess is that the psu was bad after all and it broke the mobo? It's too bad the tech didn't thoroughly test the psu, because had I known that the psu was bad I wouldn't have put the new motherboard in and most likely wrecked that one too. Now I'm sure I won't be able to even return the new motherboard so I just wasted a bunch of money on an old computer and accomplished nothing. At this point I don't want to spend anymore money on this machine, so I think I'll just buy a new machine in a month or two when I have the money and just make do with my laptop until then. And I just bought Skyrim :p.

Just one question - is it possible that there could be something wrong with a power outlet or power bar that could wreck computer components? I'd hate to get a brand new machine and have a repeat of these problems.

Thanks so much for all the advice.
 
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It is possible for the power from a circuit to damage computer electrical components if the power flucuates often. The normal voltage from a wall socket is 120vac, but it is generally considered to be OK if the variation is plus of minus 5% (114vac-126vac).

With any new machine I sell I always include a UPS and with the software included I can adjust the high and low voltage intervention thresholds. I normally keep my intervention levels fairly "tight", i.e. 110vac-130vac.

I am attaching an old pic from 2007 when the power company was working on the lines in my area. As you can see from the UPS log, the UPS intervened 12 times in a 4 week period.
 

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Here is a thread from this site that I worked on a few years ago. I'd had a number of eMachine computers brought in over the years all with blown power supplies. When the power supply failed it also took out the motherboard 90% of the time. I suspected that the problem was occurring on the +5vsb line, but I could never catch a power supply before that line failed so I could prove what I suspected.

With the help of the poster of the thread the problem was solved since he happened to catch a power supply in the process of failing. Unfortunately, he took that power supply and installed it in his Dell machine to "test" it, and it also took out the motherboard in the Dell.

http://forums.techguy.org/hardware/829268-power-supply-voltage.html
 
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