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Thread: Is Mobo Fried?

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    Is Mobo Fried?

    Friend of mine asked me to look at his son's homebrew PC. Has a known good Dynex PSU, but when the PC is turned on, there is an immediate high-pitched sound (like an alarm). The power light comes on and stays on, but the hard drive light blinks slowly (only the mobo and hard drive have power connections at this time). Can I figure the mobo is fried, or could there be something else causing these symptoms?

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    Re: Is Mobo Fried?

    <hr>immediate high-pitched sound (like an alarm). <hr>
    Are you sure this is an alarm and not a Fan going bad (CPU, Case Fan, PSU) ? Is the sound coming from the Hard Drive ? Does the MB "Beep" and if so, how many beeps (this an error code) ?

    Can you boot into BIOS and at lease see if there are any noted errors ?

    The problem could be a Hard Drive, Memory, or CPU (if CPU fan is not working and CPU is over heating). And, of course, the MB might be bad.
    Scott

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    Re: Is Mobo Fried?

    I understand your situation that after you press power button, POST (Power On Self Test) does not execute. Is it correct?
    Disconnect the hard drive. If you are absolutely sure that power supply is not the cause, start with system memory. If you have two or more memory sticks installed, remove them one by one. If you have only one stick, replace it temporarily with another compatible memory stick.
    If memory is not the cause, it can be either motherboard or CPU. It is very hard to determine which one if you do not have another good motherboard or another good CPU. Both of them are expensive and by guessing you have 50% chance you pick the right thing... <img src=/S/smile.gif border=0 alt=smile width=15 height=15>

    Good luck!

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    Re: Is Mobo Fried?

    Scott,

    >> Are you sure this is an alarm and not a Fan going bad (CPU, Case Fan, PSU) ?<<

    If the PC booted OK, but was just noisy, I might think it was a bad fan.

    >> Is the sound coming from the Hard Drive ? <<

    I'll try it with the hard drive disconnected and see what happens.

    >>Does the MB "Beep" and if so, how many beeps (this an error code) ?<<

    Nope, no beeps. Just a continuous scream.

    >>Can you boot into BIOS and at lease see if there are any noted errors ?<<

    I take it you mean boot off a floppy disk?

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    Re: Is Mobo Fried?

    kaplinb,

    >>I understand your situation that after you press power button, POST (Power On Self Test) does not execute. Is it correct?<<

    Yes, that is correct.

    >> Disconnect the hard drive. If you are absolutely sure that power supply is not the cause, start with system memory. If you have two or more memory sticks installed, remove them one by one. If you have only one stick, replace it temporarily with another compatible memory stick. <<

    OK, will try these things.

    >> If memory is not the cause, it can be either motherboard or CPU. <<

    The power supply is brand new, so unless it is faulty "out of the box", I'd have to figure a bad mobo (assuming the tests you suggested don't show anything else).

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    Re: Is Mobo Fried?

    <hr>>>Can you boot into BIOS and at lease see if there are any noted errors ?<<

    I take it you mean boot off a floppy disk?<hr>
    No - While booting you have the option to enter BIOS (usually pressing the <F1>, <Insert>, <Delete> keys - depends on your MB). You can then see if you have any errors (is the BIOS seeing the hard drive, memory, CPU, etc). Some MB also have BIOS with temp outputs to see if the CPU is OK.

    With the side of the case off, look at the CPU fan as the computer is turned on. Make sure the CPU fan is running - this is just a visual check to ensure you do not "cook" the CPU.

    Finding the source of the noise would be helpful. If you have another Hard Disk or can boot from floppies - try this to see if the hard drive is the ad actor.
    Scott

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    Re: Is Mobo Fried?

    kaplinb has some good suggestions - try them one by one.

    I should have realized you wee saying POST did not execute - do you get ANYTHING on the monitor - or do you only see a black screen ?
    Scott

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    Re: Is Mobo Fried?

    Scott,

    >> No - While booting you have the option to enter BIOS (usually pressing the <F1>, <Insert>, <Delete> keys - depends on your MB). You can then see if you have any errors (is the BIOS seeing the hard drive, memory, CPU, etc). Some MB also have BIOS with temp outputs to see if the CPU is OK. <<

    Doesn't the PC have to pass the POST test for me to get into the BIOS?

    >> With the side of the case off, look at the CPU fan as the computer is turned on. Make sure the CPU fan is running - this is just a visual check to ensure you do not "cook" the CPU. <<

    The CPU fan is running. The fan in the front of the PC isn't.

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    Re: Is Mobo Fried?

    kaplinb,

    >> Disconnect the hard drive. If you are absolutely sure that power supply is not the cause, start with system memory. If you have two or more memory sticks installed, remove them one by one. If you have only one stick, replace it temporarily with another compatible memory stick. <<

    I disconnected the hard drive, no change in symptons (high-pitched scream, no POST). Tried each memory stick alone, same. No memory at all, same. I don't have any other memory sticks like these, but it doesn't appear they're the problem, does it ? [img]/forums/images/smilies/sad.gif[/img]

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    Re: Is Mobo Fried?

    <hr>Doesn't the PC have to pass the POST test for me to get into the BIOS?<hr>
    In general yes. However, I have an ASUS MB that allows option to enter BIOS when there is a POST error. A serious error automatically enters BIOS. I was hoping your MB had the same feature - obviously not.

    From your <post#=595,652>post 595,652</post#>:
    <hr> I disconnected the hard drive, no change in symptons (high-pitched scream, no POST). Tried each memory stick alone, same. No memory at all, same. I don't have any other memory sticks like these, but it doesn't appear they're the problem, does it ? [img]/forums/images/smilies/sad.gif[/img] <hr>

    An obvious concern is the "Sream" you are hearing. If all mechanical devices were removed from the system, and fans are not causing the scream, the sound must be coming from the speaker (presuming a MB connected speaker).

    You did not mention the type of MB but did mention a new PSU. Remove and inspect the connectors to ensure no pins or sockets are damaged. If a P4 MB, ensure the 4 pin Molex connector is also correctly installed on the MB.
    Scott

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    Re: Is Mobo Fried?

    Scott,

    >> An obvious concern is the "Sream" you are hearing. If all mechanical devices were removed from the system, and fans are not causing the scream, the sound must be coming from the speaker (presuming a MB connected speaker). <<

    I even disconnected the case speaker, but the scream persists. Appears to be coming from the PSU. I checked all the pins in the 24-to-20 adapter and on the 20-pin plug to the mobo, don't see anything bent or out of socket. This particular Dynex PSU seems "slimmer" than most PSU's I've seen, and the case is done in such a way that only the Dynex can be mounted within the case. Is there any reason I can't hookup another PSU, and just have it sitting on the case frame, to see if the mobo will boot?

    >> You did not mention the type of MB but did mention a new PSU. Remove and inspect the connectors to ensure no pins or sockets are damaged. If a P4 MB, ensure the 4 pin Molex connector is also correctly installed on the MB. <<

    The CPU is an AMD, so this "Molex connector" wouldn't be an issue, right?

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    Re: Is Mobo Fried?

    A stab in the dark re: An obvious concern is the "Sream" you are hearing. If all mechanical devices were removed from the system, and fans are not causing the scream, the sound must be coming from the speaker (presuming a MB connected speaker)

    It is possible that the noise is a high frequency oscillation of the inductive coil in the switched-mode part of the psu, caused by either the winding itself being loose (they are often varnished to prevent this), or there being some adjacent ferrous material that has a induced vibration induced in it.
    If this is the case, I would expect either the frequency or volume of the 'scream' to change depending on the load the PSU is delivering.

    (Do NOT go poking around in there with a screwdriver to check out this theory please!)

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    Re: Is Mobo Fried?

    <hr>Is there any reason I can't hookup another PSU, and just have it sitting on the case frame, to see if the mobo will boot?<hr>
    <img src=/S/nope.gif border=0 alt=nope width=15 height=15>-I do this all the time when I'm testing to see if the PSU is bad.

    CAUTION:Set the PSU solidly on a table so it can not fall in the case. Regardless of the case (even a tall tower), I like putting the case on a solid surface (even on it's side), with the PSU on the same surface next to the case.You do not want the PSU falling into the case or off the case pulling on connectors plugged into the MB.

    <hr>The CPU is an AMD, so this "Molex connector" wouldn't be an issue, right?<hr>
    This really depends on the actual type of AMD processor. Quick check is if the MB has a 24 pin conncetor or a 20 pin connector and 4 pin connector right next to or close to the 20 pin connector. Based on you description, you are putting the 24 pin to a 20 pin conversion adapter and connecting an equivalent 20 pin connector to the MB - this would indicate you do not need the Molex connector. I'm alittle surprised you would need the 24 pin to 20 pin adapter, most newer PSU's have a break between the 20 pin and 4 pin connectors (or they slide apart).

    If everything was working before the PSU was added - DEFINEATLY try a new PSU just to make sure. Also, can you check the CPU to see if it is OK (provided it is not soldered the the MB) ? Remeber to ground your self agains ESD (electrostatic discharge) - or you will fry the CPU or memory. As a minimum, touch your hands on the grounded metal before touching anything in the case).
    Scott

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    Re: Is Mobo Fried?

    Leif,

    Everything you say is true - and that concerns me <img src=/S/whisper.gif border=0 alt=whisper width=29 height=17>er, about the PSU Manufacturing Quality that is

    If the "screamming" turns out to be the case as you described and not the PSU Fan, I would not want the PSU in my computer anyways - who knows when the failure or other defects may have.

    As for the screwdriver caution - TOTALLY AGREE ....

    UNLESSssssss - it is the liquid kind to be sipped while conteplating the universal electronic truth:

    <font face="Snap ITC">All electronics run on white/gray smoke that should NEVER be allowed to escape from their devices. The proof of this is when you see the smoke escape - the devices STOP working !!!</font face=snap>

    Well - that 's my story and I'm sticking with it <img src=/S/grin.gif border=0 alt=grin width=15 height=15>
    Scott

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    Re: Is Mobo Fried?

    Scott,

    >> If everything was working before the PSU was added - DEFINEATLY try a new PSU just to make sure. Also, can you check the CPU to see if it is OK (provided it is not soldered the the MB) ? Remeber to ground your self agains ESD (electrostatic discharge) - or you will fry the CPU or memory. As a minimum, touch your hands on the grounded metal before touching anything in the case). <<

    Finally threw up my hands and hauled the PC to the shop where I buy most of my parts. Took them all of 10 seconds to tell me what the screaming was: a mobo alarm to indicate that the "twin head" DVI card wasn't getting power (no onboard VGA on this mobo). But once they connected a power lead to the video card and powered the PC on, it beeped just once immediately and then powered itself off. They thought it was most likely a bad mobo, but with a diagnostic costing $89, they agreed with me that I should just get a new mobo. The kid who the PC belongs to has already bought a new mobo and processor, so I'll install them and then look through my dead machine stock and find a case I can put the "old" processor and a new mobo into.

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