Unexpected system switch off

Hi,

I wonder if someone can help...

My system will sometimes switch itself off completely shortly
after switching it on. On the four occasions it has happened it
switched off after about 1/2 an hour, once it did it twice in quick
succession. I switch back on and it seems to run fine.

I built the system myself this July. Spec:

Asus P4C800 Delux (2.8 HpThrd Intel) (BIOS ver 1006.005)
512MB memory
520W Top Power PSU (TOP-520P4)
Gainward Nvidia FX5600
Lian Li PC-60 case.
Win XP

The PSU has a selector switch on the back with A, M, and L
marked on it (for Auto, Medium and Low). It auto-adjusts the fan speed
to keep noise to a minimum.

When it switches off it does so without warning, just as if
someone pulled the plug apart from the standby power is still on (can
see green LED on MB glowing). But everything else is dead. On
switching on it starts up as if nothing has happened.

I checked the temp of the MB and CPU, both physically and
using the ASUS probe utility. No signs of overheating (the opposite in
fact). Voltage seems fairly steady (vcore normally 1.556 sometimes
1.48, +3.3 is spot on always, 5v ~4.9 and 12v ~11.7)

Also read on other groups postings about tracks being shorted
out on the P4C800 Dlx by squashed solder under the heatsink bracket.
Presumably this would cause intermittent lockups and crashes with POST
failing - I have had none of these.

My questions a

- What causes an ATX PSU to power up or shutdown? Does it detect
loading from the MB or is there a dedicated signal line that
explicitly tells it to switch on or off?

- If loading triggered, could a fault on the MB or expansion card
cause this problem?

- Also it only has ever happened between 7:30 and 8 pm in the evening.
The last time it did it, about a month after the last incident, I
noticed that the vcore voltage was fluctuating slightly (I now know
that usually they are all rock steady apart from the 12v one which
wavers very slightly). After a time it started to settle down. It
could be an overly sensitive PSU reacting to a fluctuating mains. The
other times it has done it my old computer has been on and that didn't
bat an eye lid (Pentium 90 with a pre-ATX power supply). Does this
make sense and if so what can I do about it? I have surge protectors
but they're no good in situations of low power.

- Has anyone had experience with TopPower power supplies? Are they
considered a reliable make, if not then what is considered good? Is
there a chance that switching it onto manual may make it more reliable
(dumbly letting fluctuating voltage through rather than possibly
detecting a wobbly mains and switching off just in case).

- After a switchoff Win XP doesn't seem to do any file system
checking, is it journalled? It always seems ok when I manually check
it (either a scheduled check using chkdsk or the GUI one).

Any help would be greatly appreciated.

MTIA

Tony.

If at first you don't succeed... Delegate.

Pay a visit to my home page at:
http://www.coosoft.plus.com/

My comments are below...

"Tony Cooper" wrote in message
...

Asus P4C800 Delux (2.8 HpThrd Intel) (BIOS ver 1006.005)
512MB memory
520W Top Power PSU (TOP-520P4)
Gainward Nvidia FX5600
Lian Li PC-60 case.
Win XP

Nice system!

- What causes an ATX PSU to power up or shutdown? Does it detect
loading from the MB or is there a dedicated signal line that
explicitly tells it to switch on or off?

Some PSUs, it's the on/off switch on the PSU itself. With other PSUs, a
signal from the motherboard indicates a power-on condition for the PSU.
Those types of PSU usually don't have an on/off switch.

- If loading triggered, could a fault on the MB or expansion card
cause this problem?

If the PSU doesn't have an on/off switch, I would either look to the M/B or
PSU. I don't think any other component in the system would cause that type
of fault.

- Also it only has ever happened between 7:30 and 8 pm in the evening.
The last time it did it, about a month after the last incident, I
noticed that the vcore voltage was fluctuating slightly (I now know
that usually they are all rock steady apart from the 12v one which
wavers very slightly). After a time it started to settle down. It
could be an overly sensitive PSU reacting to a fluctuating mains. The
other times it has done it my old computer has been on and that didn't
bat an eye lid (Pentium 90 with a pre-ATX power supply). Does this
make sense and if so what can I do about it? I have surge protectors
but they're no good in situations of low power.

I don't have a comment on that, as I don't know if the voltage should
fluctuate or not.

- Has anyone had experience with TopPower power supplies? Are they
considered a reliable make, if not then what is considered good? Is
there a chance that switching it onto manual may make it more reliable
(dumbly letting fluctuating voltage through rather than possibly
detecting a wobbly mains and switching off just in case).

TopPower, heard of them, but never as a "quality" make. If I'm wrong,
someone correct me, but I suspect that makes of PSU is a cheapy. I usually
stick to Antec or PC Power & Cooling.

- After a switchoff Win XP doesn't seem to do any file system
checking, is it journalled? It always seems ok when I manually check
it (either a scheduled check using chkdsk or the GUI one).

I don't think XP has a journalling file system. For that, you need Linux.
Should it do any file system checking? I didn't think it did that.

@drian.

If you have not measured those DC voltages with a 3.5 digit
multimeter, then you don't yet know what is or is not bound to
be causing problems. Motherboard voltage measurements are
only accurate enough to detect voltage changes - not read
acutal voltages. You need a 3.5 digit multimeter and data
from chart in:
http://www.hardwaresite.net/faqpowersupply.html
Also measurements on purple and green wire would be
important. Furthermore, if any number end up in the lower
quarter of limits, then further analysis is required.

Did that Top Power PSU come with a long list of
specifications? If not, then suspect it is typical of power
supplies dumped in N America missing essential functions.
Missing functions is why so many lesser power supply can sell
at greater profit for well below $80.

Power supply stability is governed by functions both in
power supply and on motherboard. Without first taking
essential measurements, one cannot even begin to guess what is
and is not reason for failure.

Of course XP also keeps system logs. What are reports from
those event logs?

Tony Cooper wrote:
Hi,

I wonder if someone can help...

My system will sometimes switch itself off completely shortly
after switching it on. On the four occasions it has happened it
switched off after about 1/2 an hour, once it did it twice in quick
succession. I switch back on and it seems to run fine.

I built the system myself this July. Spec:

Asus P4C800 Delux (2.8 HpThrd Intel) (BIOS ver 1006.005)
512MB memory
520W Top Power PSU (TOP-520P4)
Gainward Nvidia FX5600
Lian Li PC-60 case.
Win XP

The PSU has a selector switch on the back with A, M, and L
marked on it (for Auto, Medium and Low). It auto-adjusts the fan speed
to keep noise to a minimum.

When it switches off it does so without warning, just as if
someone pulled the plug apart from the standby power is still on (can
see green LED on MB glowing). But everything else is dead. On
switching on it starts up as if nothing has happened.

I checked the temp of the MB and CPU, both physically and
using the ASUS probe utility. No signs of overheating (the opposite in
fact). Voltage seems fairly steady (vcore normally 1.556 sometimes
1.48, +3.3 is spot on always, 5v ~4.9 and 12v ~11.7)

Also read on other groups postings about tracks being shorted
out on the P4C800 Dlx by squashed solder under the heatsink bracket.
Presumably this would cause intermittent lockups and crashes with POST
failing - I have had none of these.

My questions a

- What causes an ATX PSU to power up or shutdown? Does it detect
loading from the MB or is there a dedicated signal line that
explicitly tells it to switch on or off?

- If loading triggered, could a fault on the MB or expansion card
cause this problem?

- Also it only has ever happened between 7:30 and 8 pm in the evening.
The last time it did it, about a month after the last incident, I
noticed that the vcore voltage was fluctuating slightly (I now know
that usually they are all rock steady apart from the 12v one which
wavers very slightly). After a time it started to settle down. It
could be an overly sensitive PSU reacting to a fluctuating mains. The
other times it has done it my old computer has been on and that didn't
bat an eye lid (Pentium 90 with a pre-ATX power supply). Does this
make sense and if so what can I do about it? I have surge protectors
but they're no good in situations of low power.

- Has anyone had experience with TopPower power supplies? Are they
considered a reliable make, if not then what is considered good? Is
there a chance that switching it onto manual may make it more reliable
(dumbly letting fluctuating voltage through rather than possibly
detecting a wobbly mains and switching off just in case).

- After a switchoff Win XP doesn't seem to do any file system
checking, is it journalled? It always seems ok when I manually check
it (either a scheduled check using chkdsk or the GUI one).

Any help would be greatly appreciated.

MTIA

Tony.

If at first you don't succeed... Delegate.

Pay a visit to my home page at:
http://www.coosoft.plus.com/

My system will sometimes switch itself off completely shortly
after switching it on. On the four occasions it has happened it
switched off after about 1/2 an hour, once it did it twice in quick
succession. I switch back on and it seems to run fine.

I built the system myself this July. Spec:

Asus P4C800 Delux (2.8 HpThrd Intel) (BIOS ver 1006.005)
512MB memory
520W Top Power PSU (TOP-520P4)
Gainward Nvidia FX5600
Lian Li PC-60 case.
Win XP

520 watts?!?! I think I would have purchased a better name 400watt PSU.

When it switches off it does so without warning, just as if
someone pulled the plug apart from the standby power is still on (can
see green LED on MB glowing). But everything else is dead. On
switching on it starts up as if nothing has happened.

Make sure you have turned off the reboot feature of Windows XP. If you
bluescreen, it automatically restarts the PC. (My
Computer-Properties-Advanced-Startup and Recover Settings button.)