Computer diede

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Computer diede

Postby okrobie » Thu Feb 04, 2016 5:32 am

Hello, this may not be an issue for this forum, but I don't know where else to start.

When I got up this morning, my screen was blank. I tried to re boot it, but nothing happened. I unplugged it and plugged it back in but the start button did nothing. I have a power supply tester so I plugged it in to the power supply and it lit up perfectly. Where should I continue in my diagnosis? Thanks, Jim
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Re: Computer diede

Postby Karlsweldt » Thu Feb 04, 2016 11:04 am

Those power supply testers need to have a PSU in operation, for testing. The PSU is working properly?
Some quick checks: When you press the power button to start up, do you hear the PSU become active? Do you note the keyboard lights flash once or twice? Good signs.
The BIOS/CMOS battery may be dead. Typical life is 3 to 4 years, depending on use. It is only a backup for when no mains power gets into the PSU, providing the +5 volt stand-by source, which feeds the USB ports and BIOS/CMOS needs.
If the battery is dead, the system clock may not function, and CMOS settings can be lost.
Best to try a new battery, see if that is the cause. Quick fix if so.
Are all the front panel leads properly seated on the header? Is the power switch good? It is a momentary-contact type, and an open circuit when not pressed. Check with an ohmmeter for continuity when pressed. Should be near zero resistance then.
Also check that all power connections are made from the PSU to the motherboard, and all device cards and memory are seated properly. Look over all the larger capacitors, and if any are showing domed tops, lean excessively or leak, they are bad. Yes, one can go bad overnight, and the system is in trouble.
Could also be a stray bit of hardware that lodged under the motherboard, and causes a short.
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Re: Computer died

Postby okrobie » Thu Feb 04, 2016 1:25 pm

Hi Karlsweldt, I got over my resentment about this board, but I would have thought that over 10 informed, on topic posts would be enough.

Guess I wasn't very observant this morning. When I double checked the power supply tester this afternoon it shows that the -5vdc is missing and upon checking the 8 pin connector, the 3.3vdc CPU voltage is also missing.

I had a fresh spare CMOS battery so I put it in but it was no help.

Do I need a new power supply? If so, I currently have a Corsair TX750 but I see it's not a current model. What would be a good replacement? I see that the Corsair HX750 is the hot new item.

Thanks for the help, Jim
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Re: Computer diede

Postby Karlsweldt » Thu Feb 04, 2016 4:41 pm

The -5 volt source is no longer used. If needed on the motherboard, it is sourced from the -12 volt lead.
If the +3.3 volt source is not present on the PSU, then it may be bad. But there must be a minimal load on both the +3.3 volt and +12 volt leads for it to stabilize. Minimal load is about 3 amps. An old auto headlamp with dual filaments would be a good "test" load. Typically 40 watts to 55 watts, so 3+ amps each. The +5 volt supply will be stable if the +3.3 volt supply is properly loaded.
What is this 8-pin connector shaped like? Squarish, with protruding sockets, or flat, like the SATA power connector?
Only if a SATA power connector comes on a lead set from the PSU would it have the +3.3 volt lead, which is orange. Only intended for "hot swap" needs. If an adapter from Molex to SATA then no orange lead. Just the +5, +12 and returns.
There is likely one or a paired 4-pin socket(s) set near the CPU, which would require a +12 volt lead set. That is for the primary CPU voltage sources, through regulators at the CPU base.
That Corsair TX750 PSU should be adequate for the system, as long as it has equal or more wattage than the original.
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Re: Computer diede

Postby okrobie » Thu Feb 04, 2016 6:43 pm

Hi Karlsweldt, It's my understanding that the Power Supply tester has the proper loading built in so that the 3.3vdc light should be on. The TX750 I mentioned is the one that is suspect. I ordered a new power supply from NewEgg. It's a CORSAIR RM Series RM1000. The machine is an I7 with 16GB memory and I think I have been overloading it with the F@H app running all the time. It'll take a week to get here but I have my other computer to use in the meanwhile. Thanks for the help, Jim
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Re: Computer diede

Postby Karlsweldt » Fri Feb 05, 2016 9:10 am

Doubtful the F@H process caused the PSU to fail. Would be rare. But a PSU needs a great amount of cooling air, and does not get cooler temperature air like other devices may. A PSU is not immune from the 'bad caps' syndrome either.
Where subject to high heat, the rating on capacitors should be 105°C. Normally, 85°C. rating for other needs.
For the time and effort involved, not worth repairing a PSU. Recycle at a service center.
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Re: Computer diede

Postby rascard2007 » Fri Feb 05, 2016 1:25 pm

Well, begin in the beginning go to the end and then stop!

when U press the start button it did nothing, then unplug the power button conector from the board and briefly shortcircuit the two pins where the power button was conected, if nothing happens the culprit isn´t the power button (once upon a time, I spend a few days "troubleshooting" a board until i realized that the PWR button were not working!)

If the PWR Button is innocent, then see what happen to the CPU fan when U press the start button:

- if it spins for a couple of seconds or so, then the main suspect is the psu

- if it makes a tiny move, like a tic but doesn´t spin at all there a good choice of having a shortcircuited MOBO

try to get a known good PSU and see what happen
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Re: Computer diede

Postby okrobie » Fri Feb 05, 2016 3:37 pm

Hi Karlsweldt, I was not serious about F@H, I have temperature limits (CoreTemp) that I am using and they haven't tripped yet. But at full tilt, the CPU runs close to 100%.

Hi rascard2007, I relied heavily on my Power Supply tester. The 3.3vdc CPU voltage LED wasn't lighting up. I won't have access to a good PSU until my new one arrives. (Crossing my fingers)
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Re: Computer diede

Postby Karlsweldt » Fri Feb 05, 2016 4:47 pm

For the price of most of those PSU testers, I doubt they have the minimal recommended loads in them.
Physically, maybe. But the case would get very hot very quickly, and might melt down if more than 2 minutes on power!
A 1 amp minimal load, perhaps.. but that does not guarantee true regulation and output.
Per the rule standard for testing a PSU, a 20% minimal load of the rated load is required. This ensures proper regulation and true output readings.
For practical reasons, minimal could be a 1 ohm resistor at 10 watts for the 3.3 volt source, and a 4 ohm resistor at 10 watts for the 12 volt source. Add a 1.5 ohm 10 watt resistor for the 5 volt source for proper testing. And all to be wirewound!
Ohm's Law in effect here.
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Re: Computer diede

Postby okrobie » Wed Feb 10, 2016 3:26 pm

Well, my new PSU arrived today. It was DOA. It only had one output voltage the+5VSB. Very disappointing. :(

They're going to ship one right out, but they want me to pay the return postage on the bad unit. I should have returned it to NewEgg. They probably would ave paid the freight. Corsair also had me put up a credit card number to insure that I would send it back. Very poor customer service from Corsair.
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