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Mobo or CPU but which?

By ForeignBody ยท 12 replies
Jun 26, 2005
  1. My good ole Epox 8KHA+ based workhorse assembled so long ago that I cannot remember all the parts has died.

    Problems began with 2 semi sucessful starts where the CPU, PSU fans & everything else (HDD, CD) spin up but are obviously heard to be JUST getting enough juice to spin (the best word to describe it is that it stutters) AND the thing did not POST. Turned off power at the mains and switched system on again and this time it booted up, ran Windows and powered down normally. Figured it must be power supply issue so disconnected 2nd CD drive to reduce load.

    Attempted to power up again but NOOooooo:

    PSU fan does not spin up
    Mobo CPU cooling fan dead
    Mobo LED (next to the memory slots) lights up!
    Mobo diagnostic LEDs dead
    The LEDs for power and HDD on the case (connected to the mobo) light up!

    Done the basic checks which include:

    PSU - reading on all rails as expected, PSU alive and powers another test mobo, New PSU plugged into my EPOX results in the above EXACTLY. So don't think it's PSU. NO, it's not the wall plug.

    Mobo not earthed although I don't know why I bothered to check this.

    Took all components out, bit of a clean and reassembled PC but still same result.

    I did note that 2 capacitors on the motherboard were bulging and crusty on opening the case. EPOX 8KHA+ notorious for this despite it's greatness. I really don't know if it was recent or if it's been leaking for a while yet still running. Last gasp maybe?

    I can hear you say that the finger is pointing to my motherboard...........

    My question is:

    Will LEDs still light up on the mobo if it has croaked?

    Can it be the CPU and how can I be sure it is/isn't without finding another
    CPU to test the mobo with thus putting the CPU at risk? (my friends run Pentiums). CPU doesn't LOOK toasted although I'm a bit worried that attempts to power up has fried it because the CPU fan did not spin up. Heatsink was present though.

    Why does the PSU fan not spin up when connected to the mobo?

    Some power is obviously getting to the mobo but not enough for the CPU fan?

    Any help would be greatly appreciated thanks!
  2. Tedster

    Tedster Techspot old timer..... Posts: 6,000   +15

    Hard to say if the LEDs will light if the motherboard sustained damage. Usually LEDs are pretty hardy, but if the particular circuit is fried, they won't.

    Bulging capacitors are a bad sign of deteriation and they are also dangerous. Capacitors contain some nasty and quite toxic chemicals. Don't touch them or breathe any vapors.
  3. ForeignBody

    ForeignBody TS Rookie Topic Starter

    Thanks for the tip. Deterioration for sure! Anyway, took a big sniff of noxious fumes when I the casing was opened! Haha. Something smelled barbecued.... But I need to know what though!! Thought it was the PSU (1st one died on same mobo) but it isn't this time.
  4. Mugsy

    Mugsy TS Guru Posts: 401   +18

    No PSU fan. It's dead. If not, don't run anyway.

    If the fan in your power supply isn't spinning, it's dead. Anything after than is meaningless.


    Even if it is outputting power, whatever blew out the fan has likely damaged the capacitors as well, potentially outputting too much voltage to your MoBo/CPU, which could destroy them.

    Replace the p/s (450watt minimum IMHO) and report back. :)

    Addendum: P/S works on another MoBo? Then you have your answer.
  5. ForeignBody

    ForeignBody TS Rookie Topic Starter

    Appreciate the reply but as I've mentioned, I've already covered this base! I took my PSU out and tried it on another mobo. The PSU fan and mobo powered up. ALSO, I've tried a new 500W PSU on my mobo but the PSU fan does not spin either so I can't be the PSU really.
  6. Tedster

    Tedster Techspot old timer..... Posts: 6,000   +15

    Capacitors have been known to contain small amounts of arsenic, cyanide compounds, and PCBs (poly-chlorinated bi-phenyls) as well as other toxins......
  7. Mugsy

    Mugsy TS Guru Posts: 401   +18

    Try some tests.

    Hmm, that's difficult to say.

    I replaced my MoBo recently with the same problem, only to discover it was indeed my processor.

    Unless the CPU is "dead" dead, it should still work if you "under"-clock it to a lower speed. Clear your BIOS (usually there is a jumper on the MoBo... or just remove the battery... then unplug the power from the computer for ten seconds) so it reverts to its default settings (bare minimum), then plug it back in and see if it runs. Go straight into the BIOS and manually set the CPU (and/or bus speed) to its lowest setting (usually, BIOS defaults to "Auto", which is full speed) and see if the computer runs.

    If the cpu is damaged but the MoBo is good, it should run. If it doesn't, that doesn't necessarilly mean the MoBo is bad, it could still be the CPU, or any number of things. But if the cpu runs at a lower speed but not full speed, either the cpu is bad or your heatsink isn't cooling properly.

    Lights and LEDs may still light on a bad MoBo, so don't let that throw you. They don't draw their power through the cpu or ram. Usually, you will at least get "beep codes" if the MoBo is okay, but that's not a hard set rule.

    Try what I mentioned above and see what happens.
  8. Tedster

    Tedster Techspot old timer..... Posts: 6,000   +15

    I can see that. When I overclocked a 3200 processor I had, the computer would boot but the colors were scrambled.
  9. ForeignBody

    ForeignBody TS Rookie Topic Starter

    Thanks for the suggestion and will give it a bash for sure but I think I know what will happen! At least you have given me a way of finding out if my CPU is at least HALF dead. So if it runs underclocked then the CPU's probably ropey huh?

    I THINK the mobo is toast and I did guess that the LEDs lighting up only meant that certain circuits in the mobo are alive or receiving minimum power but the circuit which involves the PSU is gone, hence the PSU fan not spinning up even if you step on the power on button. I forgot to mention that I did listen for beep codes but no noise emanates the beast. Hell, it didn't even boot far enough to get beeps. I've come to the conclusion I cannot be sure whether it's the CPU or mobo short of plugging in the CPU onto ANOTHER mobo or plugging in a NEW CPU on my current mobo. My money's on the mobo. I'll just bite the bullet and buy a new mobo. Thanks.
  10. RealBlackStuff

    RealBlackStuff TS Rookie Posts: 6,503

    Have you tried another powercord from wallsocket to PSU?
  11. ForeignBody

    ForeignBody TS Rookie Topic Starter

    Erm...I suppose it's worth a try although LEDs on the mobo light up so it's UNLIKELY the powercord's at fault because I'd expect no power at all...
  12. RealBlackStuff

    RealBlackStuff TS Rookie Posts: 6,503

    LEDs come on almost by holding them next to a powercable. Try it anyway.
  13. ForeignBody

    ForeignBody TS Rookie Topic Starter

    Solved the problem-ish.

    The problem was the motherboard. Installed new mobo and problem solved.
    Here is a simple summary for those who may encounter the same problem.

    Mobo was and Epox 8KHA+ which in itself if known for blowing capacitors and frying up.

    It's likely to be the mobo:

    1. Because the PSU fan does not run AND you are SURE the PSU is OK then probably the motherboard is at fault because a circuit needs to be completed on the motherboard for the CPU fan to come alive.

    2. Because the CPU fan is dead BUT the PSU is OK

    3. Just because lights on the motherboard (LEDs) come on doesn't mean it isn't dead

    4. When you see obvious signs i.e leaking/bulging capacitors

    Hope it helps someone. Thanks for everyone's input.
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