X5DA8 Failure

I am running a SUPERMICRO X5DA8 board with two Pentium4 XEON processors, and
the board has developed a problem. The computer will not run any more, because
the board faults the power supply.

With the computer OFF, the power supply produces a loud clicking sound, as it
goes into protect, probably due to overload. If I remove the 5VSB connection
from the main board, the clicking stops, the power supply starts and all fans
and drives run - but the computer won't boot - apparently the board cannot run
without power on the 5VSB connection.

I can measure the resistive load from Pin 9 of the ATX power connector (on the
board) to ground. It is about 9 ohms, which is well within the loading
capacity of the 5VSB on the power supply. The power supply itself is an NMB,
model GM460WTXW01SSV. The 5VSB output is rated at 2 amps, but in tests I can
load it much higher - I have put a 1 ohm load on it, and measured 5 amps of
current for a couple of minutes, without the power supply overloading or going
into a protect mode. As a final test, I have used one of the other 5V outputs
of the power supply (with the board powered up) to supply the 5VSB connection,
and this shuts off the power supply instantly. I believe it is safe to say
that the power supply is not the cause of the problem.

I have the jumpers for USB and JPWake both set to 5V source (not 5VSB), but I
have tried all configurations of these jumpers, with no change. I have
examined every millimeter of the board for damage, visible shorts or stray
wires, dirt etc, and I have vacuumed the board on both sides to make sure
there is nothing conductive shorting this connection.

The condition persists even if I remove everything from the board - both
processors, all memory modules, all fans, drives etc. I have checked the
battery on the board, and it measures just over 3V.

What is going on????

Thanks,
G Faris

In article <ctd97l$18v5$1@biggoron.nerim.net>, farris DeleteThis @nonum.com (G Farris)
wrote:

 > I am running a SUPERMICRO X5DA8 board with two Pentium4 XEON processors, and
 > the board has developed a problem. The computer will not run any more,
because
 > the board faults the power supply.
 >
 > With the computer OFF, the power supply produces a loud clicking sound, as it
 > goes into protect, probably due to overload. If I remove the 5VSB connection
 > from the main board, the clicking stops, the power supply starts and all fans
 > and drives run - but the computer won't boot - apparently the board
cannot run
 > without power on the 5VSB connection.
 >
 > I can measure the resistive load from Pin 9 of the ATX power connector
(on the
 > board) to ground. It is about 9 ohms, which is well within the loading
 > capacity of the 5VSB on the power supply. The power supply itself is an NMB,
 > model GM460WTXW01SSV. The 5VSB output is rated at 2 amps, but in tests I can
 > load it much higher - I have put a 1 ohm load on it, and measured 5 amps of
 > current for a couple of minutes, without the power supply overloading or
going
 > into a protect mode. As a final test, I have used one of the other 5V outputs
 > of the power supply (with the board powered up) to supply the 5VSB
connection,
 > and this shuts off the power supply instantly. I believe it is safe to say
 > that the power supply is not the cause of the problem.
 >
 > I have the jumpers for USB and JPWake both set to 5V source (not 5VSB), but I
 > have tried all configurations of these jumpers, with no change. I have
 > examined every millimeter of the board for damage, visible shorts or stray
 > wires, dirt etc, and I have vacuumed the board on both sides to make sure
 > there is nothing conductive shorting this connection.
 >
 > The condition persists even if I remove everything from the board - both
 > processors, all memory modules, all fans, drives etc. I have checked the
 > battery on the board, and it measures just over 3V.
 >
 > What is going on????
 >
 > Thanks,
 > G Faris

Disconnect the ATX power connector from the motherboard. Get a
multimeter, and check the resistance from each rail to ground,
on the ATX power connector. Leave everything in place for your
first measurements (just disconnect the PSU from mobo). Maybe
you'll find +12V, +5V, or +3.3V is partially shorted to ground,
or even one of the two mostly unused rails. (Phone Supermicro,
and see if they can tell you what "normal" readings are for your
model of board. My experience in the lab, is electronic assemblies
have fairly good clustering in terms of those resistance numbers,
and you can get some health information about a board, simply
based on the resistance reading from each power rail to ground.
Perhaps in your case, the symptoms will be quite obvious, with
a dead short indicated in one of your readings.)

Remove components from the motherboard one at a time and measure
the rail that was shorted again. Continue until the motherboard is
empty. (Place all components in antistatic bags as you remove
them.)

If the board still reads a short on one rail, remove the motherboard
from the case. Place it on top of a piece of cardboard. Measure
the shorted rail again, and see if the problem was a short underneath
the motherboard somewhere.

If it is still dead, you could have a switching converter failure on
the motherboard. Perhaps a MOSFET is fried or something. With your
empty motherboard in hand, prepare the shipping container, and
send it back for repair.

If you get a new board to replace your current one, don't forget to
measure the resistance of each rail to ground when the new
board arrives. Write the values on a piece of paper, and stick the
paper inside your computer case. If you have trouble in the
future, you'll now know what the "normal" values are.

To debug a motherboard like this, you need a schematic and a layout
for the board, plus the CAD tools to load the design and allow
cross probing. On a complex board, that is the only practical way
to associate schematic to components in a time efficient manner.
If you had a paper schematic, it would have to be extremely high
quality, with abundant cross refs and component locations on it,
and most modern schematics are useless in this respect. If you send
the board back to the manufacturer, they can probe with a bed of
nails, and find the short in seconds. If copper planes are shorted
somewhere, they'll likely throw the board out.

Something else you should consider, is the percentages are
that your power supply has failed, and not the motherboard.
Before wasting good money, only to have the manufacturer tell
you "no fault found", try another power supply. It is a
simple test that could save you a lot of time. (Sometimes
power supplies become weak, and they cannot take a decent
load. The power supply may operate at no load, but protect
itself before the rated limits are reached.) Since you have
a multimeter, don't try the power supply swap if you are
already reading a dead short on the mobo

Paul<!-- ~MESSAGE_AFTER~ -->