PSU or MOBO fault?

Richard William · 26 Jun 2015 at 07:00

Hi,

I’m trying to diagnose a fault that has occurred on my system, short history, bought it second hand have stripped it back to individual components cleaned inspected and rebuilt. System worked perfectly after rebuild and loading a fresh install of win 8.1. had one issue it wouldn’t connect to the LAN, MOBO has the Bigfoot killer e2100 chip onboard, ended up plugging in a TP-link wireless board and everything seemed to be working fine.

Next day tried to start system and it just seems to be in a continuous on off loop at Post.Have removed everything from the MOBO apart from the CPU and Cooler, tried to boot and it’s still doing the same thing just looping starts looks as if it’s trying to post then shuts down, starts tries to post etc. The only thing I haven’t got is a case speaker so am not able to hear any diagnostic code from the MOBO. Any ideas from past experience would be much appreciated.

System spec is,

Intel 2nd Gen i7 sandybridge 2600k 3.5Ghz
Gigabyte z68 G2 sniper
Gpu: 4gb Msi R9 290 Pro
16gb (2x8gb) Avexir core ram 2133mhz
Psu: 700w coolermaster silent pro
SSD: Crucial MX100 250gb
HHD: Samsung F1 1TB
Cpu cooling: Corsair H100 fitted with Silverstone SST-FQ121 FQ Series 1225 PWM Fans
Gpu Cooling: Corsair H50 with nzxt g10

Borealis · 26 Jun 2015 at 07:48

Have you got 1 stick of RAM in? The machine won't POST or reach BIOS unless it can detect memory.

You can also try clearing the CMOS memory and see if that has any effect.

Richard William · 26 Jun 2015 at 08:04

yes have tried both with a single stick and clearing the cmos manually with jumper.

Borealis · 26 Jun 2015 at 09:12

Have you got another PSU you can try? If it does it with another PSU, then it's probably not the PSU.

Richard William · 26 Jun 2015 at 09:36

Unfortunately I have not got a spare my older PC has a 500w PSU but it only has one four pin ATX connector this system with the 700w PSU has two and the MOBO has both plugged in.

Jonnygrunge · 26 Jun 2015 at 10:44

Borealis said:
Have you got 1 stick of RAM in? The machine won't POST or reach BIOS unless it can detect memory.

You can also try clearing the CMOS memory and see if that has any effect.

One of the first things it does in POST is check for extended RAM after the jump command! This would not cause a reset!

Could be a few things, PSU, CPU overheating. Dust in connections, or the motherboard itself.

I would bet on the PSU, however.

Borealis · 26 Jun 2015 at 11:48

Fair point. I've never tried booting without RAM installed before so I assumed it would cause a reset.

Wouldn't a CPU overheat just cause a thermal shutdown rather than a reset?

Richard William · 26 Jun 2015 at 12:02

Jonnygrunge said:
One of the first things it does in POST is check for extended RAM after the jump command! This would not cause a reset!

Could be a few things, PSU, CPU overheating. Dust in connections, or the motherboard itself.

I would bet on the PSU, however.

would my spare 500w PSU with just the one 4 pin ATX connection be enough to power the basic system and boot it with ram inserted?

Borealis · 26 Jun 2015 at 12:08

It should be OK if it's just the CPU, RAM and CPU cooler. If it POSTs successfully, then you should be able to isolate the PSU as the problem.

Jonnygrunge · 26 Jun 2015 at 14:53

Richard William said:
would my spare 500w PSU with just the one 4 pin ATX connection be enough to power the basic system and boot it with ram inserted?

Should be OK to test, this supplies 12V to the CPU Vreg's, it might not work if the motherboard expects 2 12V connection however.
I'd give it a bash to help rule out the problem.

Richard William · 26 Jun 2015 at 15:15

Ok have swapped out power supplies fault still exactly the same. have also connected a case speaker which is giving constant short beep. Looks as if we are getting closer to the fault. I have also fitted the 700w power supply into the old PC and it's running perfectly.

Richard William · 26 Jun 2015 at 15:19

I'm going to pull the MOBO out of the case and have a better look, the one thing I haven't done is remove the CPU to inspect the pins and socket is there any chance that might be a problem?

Jonnygrunge · 26 Jun 2015 at 15:53

Do you get any audible beeps with no RAM (3 beeps of 3) to indicate the lack of extended memory.
Be careful if you are looking at the CPU (PGA - Pin Grid Array socket) the pins are easy damaged. A wee check of the pads on the back of the CPU for dirt etc. sometimes even just re-installing the CPU, the PGA pins will re-cut into the back on the CPU can give you a better connection.
Try the VGA card in a different slot, also try cleaning out the RAM slots and gold fingers on the DIMMs - Good luck

Richard William · 26 Jun 2015 at 16:24

without the ram it was a constant what sounded like short beep, will check all of the above thanks so far for the help.

Richard William · 26 Jun 2015 at 18:02

have just pulled the CPU looks as if there's TIM on one section of the socket I have never removed it so can only assume it was already on there is this likely to be terminal?

Jonnygrunge · 26 Jun 2015 at 20:25

Could be shorting out data bus lines, some ArctiClean may shift it, or "Ethanol" Isopropyl Alcohol (propan-2-ol) or IMS (Methylated Spirits) will do the job. A very sharp scalpel blade may help to also loosen it.

Richard William · 27 Jun 2015 at 08:20

hi thanks again for the help I'm out and about for most of today will pick up some cleaning product and have a look at it later on...

Richard William · 29 Jun 2015 at 06:30

have cleaned the Tim off and replaced the mobo everything seems to fine... thanks for all the help I'm quite pleased actually my first full strip and build and am learning all the time. ... I'm going to start another post on the memory section of the forum I'm having a problem with the XMP profile for the ram.

Jonnygrunge · 29 Jun 2015 at 10:15

Well done, glad to have helped!