PC wont start up.

[mlee55]

The problem is this.
1. All cables connected, power at the wall socket on and switch at the back of the PC on the power supply on.
2. Press power switch on PC case and it lights, but no HDD light illuminates.
3. Power down and opened the case and re-applied the power and observed the following: Fan on CPU and graphics card start up and hear a single click from the HDD, but still no lights other than power light illuminate.
4. Using multimeter observed the following voltages from the P1 connector from PSU to motherboard - RED 5.1, Orange 3.3, Yellow 12.1, Grey 5.1, Purple 5.1, Blue -12, Brown 3.3 and finally Green 4.1 volts when switch on back of of PSU but not applied at front of PC, when power is applied at the front of the PC the voltage drops to 0. All molex and mini molex voltage outputs are present and correct only connectors not checked are those for SATA drives as unable to insert multimeter probes.
My first thought was Power supply, my tests with multimeter seem to dispell this I am now thinking any of the following:
a. CPU (pentium dual core 945 3.2 GHz) is fried
b. Motherboard (MSI 7173) is fried, or
c. HDD drive (250 GB SATA) is fried.

Does anyone have any ideas?

Thanks in anticipation (sry for any typo's)

 

[ChrisJ78]

If there are no beeps and monitor won't come out of standby, most likely the Motherboard. If the processor was fried, there would normally be beeps or a sequence of light flashes or the green led would be red.

Try removing everything and plugging back in, but my guess would be motherboard. Happened to me a couple of times now.

 

[Rechar]

primary suspects are Memory or Motherboard. If you have more than one memory stick, try rotating them to eliminate them as a cause.

Definately not your HD, your computer would still POST without it functioning correctly.

 

[mlee55]

Hi and thanks for the replies.

Firstly I don't know if this is relevant? PC was switched off Sunday evening, on MOnday we has a brief thunder storm ans later that day was when the PC would not start. The PC was connected to the socket on the wall. Could this have been the cause?.............

...........I can confirm there are NO bleeps when the machine is powered up!!

Done some more investigations - Unplugged IDE cable from DVD drive and power to comes on and can open try, with IDE plugged it nothing happens.

Got a separate DVD drive and power is applied to it with IDE cable both plugged in and unplugged?

Swapped IDE cable and also used secondary controller, still nor joy.

Unplugged SATA cable from HDD nothing happens i can't tell if power is going to it, although i think i can hear the drive click once and then start spinning.

Cleaned the contacts on the memory modules, swapped them around and also used old modules i had from when i upgraded the memory, still no joy.

thanks

 

[Rechar]

When you said that the voltage drops to zero when powering on what did you mean exactly? Have you tested the voltages of each rail while the PC is powered up, or do they all register zero?

 

[ChrisJ78]

Sounds like the board to me still. Is it a Gigabyte board?

 

[mlee55]

The green shows 4.1 volts when the cable is in the rear of the PC and switch at the rear on the PSU is on.

Immediately the power is applied using the button on the front of the PC (power up) the voltage drops to 0 on the GREEN only the rest show the voltages as per the first post on here.

Have seen on wikipedia http://en.wikipedia.org/wiki/ATX that Green is for POWER ON and quotes the following

"PS_ON# or "Power On" is a signal from the motherboard to the power supply. When the line is connected to GND (by the motherboard), the power supply turns on. It is internally pulled up to +5 V inside the power supply."

Not entirely clear to me what this means?

 

[xr4x4]

as a computer engineer of 7 years......

thunder storms kill pcs....

has it got a dial up modem? was it connected, if so unplug it.

unplug everything thats not needed, like hard drives, ide and power, floppys, dvds, any cards except vga card if you have one, has it got onboard vga and you have a added vga card, remove this if so.

you now need to test the psu with a plug in psu tester (maplins) or try another known good working psu. a multimeter will not test it correctly.

if psu is fine, then its most likey mobo, ram or cpu. or all.

 

[timtheenchanter]

Ill second in on the PSU, we have had a few go at work, machine would still power on (ish) but not boot, turned out only one voltage rail was affected.

 

[xr4x4]

Ill second in on the PSU, we have had a few go at work, machine would still power on (ish) but not boot, turned out only one voltage rail was affected.

indeed.. even a working (i use the word loosely) can have a voltage fault.

 

[topbloke77]

Ill second in on the PSU, we have had a few go at work, machine would still power on (ish) but not boot, turned out only one voltage rail was affected.

As a IT boffin, this would also be my 1st bet. Seen this many many times. Most faulty RAM issues will give BIOS BEEPS.

PSU at fault - 1st suspect
MB blown due to thunderstorm zapping the phone line - 2nd suspect

Check in this order

 

[mlee55]

Hi me again.

Ok the phone line does not connect to the PC, it is located down stairs in the hall and I conect to the internet via Wireless to the router.

I have got hold of a Thermaltake DR Power PSU tester, Part No A2358.

I plug in the P1 connector and all the green LEDs light up with the exception of the -5 Volts and get a weak bleep. According to the (only) documentation supplied, all lights should light and bleep should be heard. http://www.thermaltake.com/product_...C_00001036&id=C_00001037&name=dr.power&ovid=n

Should the -5 Volt light? Should the bleep be loud? Any more ideas, don't want to splash out on a ne PSU if it is indeed working.

Cheers

 

[mlee55]

Hi all

Just fitted new (boxed retail) PSU but still the same original problem exists. Does this mean it is the motherboard?

Frustrated been 3 weeks now no PC just old laptop

Cheers

 

[mlee55]

Hi

Took the PC to the local (independant) shop and a new motherboard is being fitted tomorrow.

Thanks everyone for your input.

Matt

 

[gbrown100]

Just FYI, quite a good way of seeing whether it is a MB or supply problem is simply to keep and eye on the processor / case fans when you switch on. With an ATX supply it is designed to immediately cut the power to the computer if it detects a fault, if the problem is a faulty component you USUALLY see the fan twitch very briefly before the circuitry has time to detect the fault and shut down. With a power supply problem you would normally get nothing at all.