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power supply running, no video, no beeps, front panel switch does noth


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#1
wysiwyg111

wysiwyg111

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Hello All:

experienced user here with motherboard problem. working on a friend's system and having power issues.

SADLY SUSPECT THAT BOARD OR CPU OR BOTH ARE NOW DEAD.

had spent hours and hours fixing overly loaded and partly functioning Windows XP install with great deal of success (way too many installed programs, many extra startup programs loaded, conflicts with various installs, you name it). went through all hardware and connections as well doing many minor fixes and was just about to return to owner, a friend.

while testing some final adjustments, the entire system shut down. no p/s fan, cpu fan, ho hd spins, no video, nothing. after removing one device after another to get down to only mbd, supply, and switch, still nothing. pulled all power connections, put loaner supply hanging out of case with just ATX power connector to motherboard/cards and front panel switches and powered up. figured it was dead supply (would not have been surprised at this; was pretty sure supply was too wimpy, 350W, for this massive power hungry machine, so got new 500W supply.

both supplies have rear real power switch, btw. kind of important.

get new supply in machine, all plugged in, everything ready. apply power, everything powers on right away from only real power switch. no POST, no video, no beeps (has true mbd speaker, not talking abut sound card), nothing. entirely ignores front panel switch, both reset and power.

removed all connections and devices from chain, no drives, no cards, no kbd/mouse/etc. now only mbd, front panel power sw, and still nothing. rear power switch turns on system (LED on mbd and cpu fan start running) and no front panel switch action. have tried different switch as well, but clearly that isn't really an issue anyway.

currently testing/about to test old and new supplies on bench out of box while only connected to dummy tester drives and powering on by momentarily shorting "power on" (pin 16 on 24 pin connectors, green wire) and ground. will observe voltages and behavior and report back shortly.

don't think specs on the machine are that important in this situation since problem is so generic, but here they are:

ASUS AMD mbd M3A78
AMD quad core cpu 2.3 GHz
1 2G DDR2 RAM DIMM
3 HD (Max 80G, Max 160G, WD 160G)
2 APATI DVD-RW
Promise dual IDE PCI
NVIDIA PCI Express x16 video
ATI tv tuner PCI
Soundblaster PCI (redundant to mbd sound)
PS/2 kbd
USB mouse
many external USB HD (not here, left at other location)
USB and printer port HP printers (also not here)
crazy huge [bleep] case w/ many fans and a couple lights

haven't seen schematics or other specs of mbd to know what this behavior means.

am probably going to swap out motherboards in his box to get it back to him sooner than i may have results on this board.

if possible, please include a CC to me as well as a response here; have "send email from members" turned on in profile.

thanks in advance!
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#2
Digerati

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rear power switch turns on system (LED on mbd and cpu fan start running)

Something is wrong right there. Note the ATX Form Factor standard calls for +5Vsb standby power be applied across several points of the motherboard when the PSU is simply plugged in (and master switch on back, IF equipped, is set to on). This allows for things like the front power switch to work, and various "Wake on" features. So the LED on the motherboard is indicating the +5Vsb is present and that is good. But - the fans should not start spinning until the motherboard signals for the PSU to fire up, and that is done with the front panel switch shorts the two pins on the motherboard's front panel I/O header.

If the fans spin just by turning on the PSU and the front panel switch is disconnected, that indicates to me a problem with the motherboard.

Integrated motherboard speakers do not take the place of integrated sound or sound card. The integrated speaker is for BIOS beeps - and if not getting any, that is not good either.

Are you 200% sure, that is, have you double checked to ensure you have correctly attached the front panel switch wires to the motherboard's front panel I/O header? There are several M3A78 versions. You might check the board for the specific model and see if you can find a manual on Asus' website. Unfortunately, that appears to be a commercial (OEM) version, and they don't always make those manuals available.
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#3
wysiwyg111

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rear power switch turns on system (LED on mbd and cpu fan start running)

Something is wrong right there. Note the ATX Form Factor standard calls for +5Vsb standby power be applied across several points of the motherboard when the PSU is simply plugged in (and master switch on back, IF equipped, is set to on). This allows for things like the front power switch to work, and various "Wake on" features. So the LED on the motherboard is indicating the +5Vsb is present and that is good. But - the fans should not start spinning until the motherboard signals for the PSU to fire up, and that is done with the front panel switch shorts the two pins on the motherboard's front panel I/O header.

If the fans spin just by turning on the PSU and the front panel switch is disconnected, that indicates to me a problem with the motherboard.

Integrated motherboard speakers do not take the place of integrated sound or sound card. The integrated speaker is for BIOS beeps - and if not getting any, that is not good either.

Are you 200% sure, that is, have you double checked to ensure you have correctly attached the front panel switch wires to the motherboard's front panel I/O header? There are several M3A78 versions. You might check the board for the specific model and see if you can find a manual on Asus' website. Unfortunately, that appears to be a commercial (OEM) version, and they don't always make those manuals available.


well, this is the standard M3A78. i found the manual right away and it is the same one as (we) have. the front panel switch is a two pin jumper and is pretty straight-forward. it was the right jumper a little while ago and have tested/checked several times that i am on the right pins. and even tried with a different momentary sw.

tested, tested, tested. have re-checked everything even after two different good sleeps (sometimes weary eyes miss things). lots of testing all yields same result. seems mdb or cpu or bth are dead.

acting very odd. think i'm going to swap out mbd with another, get his machine back to him with loaner board, and Dx further.

any ideas on where to look first?

[yes, know the sound card/pc speaker drill; that's why i mentioned that it was the pcsk that was not giving beeps lest someone think i was thinking that sound card would handle system beeps.]

Regards, -wysiwyg111
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#4
Digerati

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the front panel switch is a two pin jumper

Yeah, that is a standard ATX configuration so any ATX case will support any ATX motherboard. What is not standard is the pinout or labeling on the motherboard's front panel header, or the case's wires. So if sure you have the correct two wires and pins on the header, then no problem there.

As I noted, the fans should not be spinning unless the computer is powered on. When in standby mode, that is, simply plugged in and the master switch in back set to on, no fans should be running. Since you tried a second PSU, I think the motherboard is gone.
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#5
wysiwyg111

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the front panel switch is a two pin jumper

Yeah, that is a standard ATX configuration so any ATX case will support any ATX motherboard. What is not standard is the pinout or labeling on the motherboard's front panel header, or the case's wires. So if sure you have the correct two wires and pins on the header, then no problem there.

As I noted, the fans should not be spinning unless the computer is powered on. When in standby mode, that is, simply plugged in and the master switch in back set to on, no fans should be running. Since you tried a second PSU, I think the motherboard is gone.


Dear Digerati:

yes, unfortunately, that is my thought too. i wonder if there is a way to fix it. at the moment, i don't have another motherboard that accepts that cpu type or even the DIMMs. if i could find schematics, i would at least have a fighting chance of fixing it or at least getting it to work partly. that would be if any only if, the board is not blown completely, the CPU is ok, and the circuitry to do the power-on/off stuff is relatively simple. i don't really hold out much hope for either of those.

i also am sort of at a loss to figure out if the board is really blown or not. i have taken it out of the box (put a loaner board in my friends box for the meantime and got it back to him), so i can bench test it now.

thanks for replying.

anyone else have any ideas out there?

Regards, -wywiwyg111
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#6
Digerati

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In the old days 20+ years ago, schematics were available and motherboards were so expensive, it was financially feasible, and responsible to spend manhours troubleshooting and repairing them. Today, manufactures don't publish schematics and it is cheaper to simply replace them.

The motherboard makers have mockups and computerized troubleshooting equipment for their own boards, but unless you see a burned out component, it is not likely you will be able to find the fault or fix it.
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