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motherboard repair

Discussion in 'Motherboards & Memory' started by gmastra100, Jul 31, 2013.

  1. gmastra100 New Member

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    Hi
    I recently acquired a "new" motherboard, however when I installed it , No fans or POST, no sound just the green stby power LED. I paid via paypal so I opened a case. To my amazement , I was given a full refund and told I could keep the board.
    So I am on the lookout for another 990FX board bargain. ( recently saw a gigabyte UD-7 go for sub £100 )
    My question
    Has anybody attempted repairing a Sabertooth 990FX Rev 2.0 ?
    Before I consign it to the wheelie bin, I wanted to check there wasn't a regulator chip , that may have acted as a "fuse"
    I am an electronics engineer so have the skills to repair motherboards ( not BGA )
    but any help gratefully accepted.

    thanks
     
  2. ruff0r

    ruff0r

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    Rest the bios, Take out the battery....look at the jumpers on the board if they are corectly and none missing. (if it has any)
    If that dosn´t help you may make an Asus support ticket with the serial number you hopefully have and try to get it replaced.
     
  3. drdeathx

    drdeathx

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    It could be a grounding problem. Pull the board out of the case and build the system on the motherboard box. Sometimes there is a standoff grounding or a wire to the case power/reset button. building it outside take grounding issue out of the equation. Good Luck.
     
    95Viper says thanks.
  4. Hood

    Hood

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    If the BIOS is corrupt, it might exhibit these symptoms, since it would have no POST routine instructions. I assume you did a CMOS reset, and I assume you tried to re-flash the BIOS (Asus USB Flashback requires only standby power to the naked board). If you tried all that to no avail, it could still be a bad BIOS chip. That board uses a socketed BIOS chip, which can be had for $10-$15 on eBay or from Asus.
    Just a thought, might be a long shot, but worth a try if it's not a lot of trouble
     
  5. drdeathx

    drdeathx

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    The bios is NOT corrupt. It is a new board and won't boot. He can't flash the bios if it don't boot.
     
  6. McSteel

    McSteel

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    So the board is receiving +5VSB successfully, and is resting in stand-by, but won't "pull up" to S0 (on-state)?

    You know, I has an Asus M2N-E a while ago that had the same symptoms. So I took out a DMM and screwed around with checking for fused FETs, open chokes, failed caps etc, I even brought in a scope with who-knows-what in mind...

    Then I just stopped for a minute and thought I'd force it on. I took a large flat-head screwdriver and shorted pins 16-17 (PS_ON and GND), held it like that for about 10 seconds (while the CPU fan spun at full speed), and it turned off after I removed the short.

    Amazingly, after turning the board over, shorting the power button pins on the front panel pinout, the board booted normally! To this day I don't have a reasonable explanation, but the board still works (in a friend's PC).

    Perhaps it's not such a bad last-ditch effort...
     
  7. Hood

    Hood

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    Asus USB Flashback will flash the BIOS without RAM, CPU, or anything else installed, using only +5v standby power. This very useful feature is included on most Asus boards since late 2011 (including the Sabertooth 990FX). It saved my ass a couple of times on my P8Z77-V board after failed overclocks.
    Also, the OP stated that this was a "new" board (new in quotes), by which I assume he meant "used but new to me" since it appears to have been bought on eBay - they gave him a complete refund, but let him keep the board - that doesn't sound like brand new, it sounds like the seller knew the board was bad.
     
  8. Jetster

    Jetster

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    Try different memory. I had two boards that the memory that should have worked didnt.

    Also buy a new bios and replace the chip. You can get one from E bay for $10. Its worth a try. Maybe its just a dead BIOS and you cant flash that.

    If the BIOS has been erased it will not post and wont flash
     
  9. brandonwh64

    brandonwh64 Addicted to Bacon and StarCrunches!!!

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    Just RMA to asus, they go by serial number so I would assume a 990FX would be under warranty
     
    Jetster says thanks.
    Crunching for Team TPU
  10. drdeathx

    drdeathx

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    Very good! It may be a memory compatability issue. Never thought of that! OP post all the system specs........
     
  11. gmastra100 New Member

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    Hi Thanks for the quick reply,
    I removed the battery and reset the bios chip, changed CPU, RAM
    Checked the board over for obvious burnt tracks/ components but the board looks good.
    Not sure if I can re flash the bios chip as nothing happens.
    Do you think I can RMA the board as it was from an auction site with no info. just the board.
    I have the serial number 60A*****AC0F.
    I have found a bios chip on ebay that I can buy, what are the chances it works ? As I fixed a friends computer that had a bios chip issue, but at least the fans were on.

    If I go the RMA route, where are the forms?. On the asus web page I could only see the RMA for notebook form?
    https://eu-rma.asus.com/pick_eu/uk/
    ( if someone could provide me a link it would be great)
     
  12. gmastra100 New Member

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    looks like I was reading the wrong s/n
    If I do not have box , can I( get it from the board ?
     
  13. cadaveca

    cadaveca My name is Dave

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    look on lowest PCIe slot, or 24-pin connector, or rear I/O towers.
     
  14. gmastra100 New Member

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    Hi
    the only numbers resembling a s/n are near the dram
    0****8-01626-MB0CT0-A)C which is not being accepted as a s/n if I try to register the board
    and the 60A number with a barcode on a printed label on the power connector.
    I thought this was the S/n but again its apparently not the correct format
     
  15. Hood

    Hood

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    Did you try re-flashing the BIOS, specifically using Asus USB Flashback? This is a new utility that only requires +5v standby power, but I think it's only available on R2.0 versions of this board. If you have the original board version it's not possible to do it this way.
     
  16. gmastra100 New Member

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    Hi I have a rev 2.0 board, I have downloaded the manual and cannot see how to flash bios with stby power only.
    I have ordered a new bios chip which should arrive in the next week.
    Assuming tha bios is corrupt I am still puzzled why there are no fas running on power up.
    I keep thinking that with all these fancy vrm chips and power saving modes, there is a hardware fault in a regulator chip .
    Will keep you updated
     
  17. Hood

    Hood

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    Sorry, I was misled by this photo, it has in large letters "USB BIOS Flashback" next to the first RAM slot. On my Asus P8Z77-V, USB BIOS Flashback is a utility which uses a dedicated button on the board and a dedicated USB port to flash the BIOS using only standby power, no CPU or RAM needs to be installed and you don't have to boot into the BIOS, so you can flash even an apparently dead board (if the green power LED will light). On your board it seems to mean just that you can use a thumb drive to load the BIOS from Windows or from a BIOS utility. But it's worded the exact same way on both boards. http://rog.asus.com/wp-content/uploads/2012/08/sabertooth-990fx-r2-overview1.jpg
     
    Last edited: Aug 4, 2013
  18. gmastra100 New Member

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    No probs,
    I have ordered a new chip. So will see if BIOS is issue next week
     
  19. itsakjt

    itsakjt

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    Its not a BIOS issue. Had it been, it would have powered on and fans would spin. Disconnect the CPU voltage connector(2*2 or 2*4 pin) connector and start the board. If fans spin(obviously, it will not POST), then you have got a short circuited VRM which is easy to fix. Also if you don't mount the CPU properly, then some board won't start too thinking there is no CPU.
     
  20. gmastra100 New Member

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    Hi,
    what do you meant the " CPU voltage connector(2*2 or 2*4 pin) connector " are they the
    12V ( I have 2* 4pin)

    I was going to try it with not CPU/Ram or graphics card as I read that it should still post.
    My son is using his old comp, so will wait until I get the chip, ( so I don't dismantal his computer several times)
    But will try what you suggest first.
    thank you
     
  21. itsakjt

    itsakjt

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    Yes I meant that 12V connector. And do try it.
     
  22. gmastra100 New Member

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    Hi all,
    quick update,
    tried board without the 12V connectors , and CPU/RAM fitted and not fitted, but still no fans.
    I am waiting for the bios chip as my last hope.
    Re-checked the board for signs of cracks and heat distortion on motherboard but looks new.
    All chips , caps OK, even battery was 3V
    Have not removed North and south bridhe heatsinks to check components under them. Will wait for new bios chip.
    Please keep giving me ideas to try, very much appreciated.
     
  23. itsakjt

    itsakjt

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    After checking the BIOS chip, if it does not work then try the last resort. Force power on it. Just plug all connectors of the PSU to the board. Take a small wire and join the green wire of the PSU to any black wire. See what happens.
     
  24. Aquinus

    Aquinus Resident Wat-man

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    Even if the BIOS is corrupted you should be able to use BIOS Flashback to flash it by using the flashback button by a particular USB port. I needed to flash the BIOS on my P9X79 Deluxe before it would even POST.

    This might be useful to get started: http://event.asus.com/2012/mb/usb_bios_flashback_guide/
     
    itsakjt says thanks.
  25. gmastra100 New Member

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    hi just an update.
    Still waiting for bios chip expected next week, so I thought that I would try shorting the green wire to the black.
    Whilst I shorted the wires, ( only temporarily) , the fans came on , the cpu led was on, So I think it may be the bios, any other things I should try ?
    The 990fx boards don't have the flashback so cannot re-flash with just standby.
    Thank you, any more thoughts appreciated.
     

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