PC power suplies


D

Desmond

Hi I have a tower unit with a 500W PSU that I think is failing. After a wile the PC crashes and I get a blue screen. This happens after it has been onfor a while. On one occasion it went dead completely but it started up when I got to it.

I don't think it can be anything else. Not sure if an over heating CPU would cause the power to go off.

If it is that can I replace it with a bigger PSU 700W or 900W? is the size and foot print the same on these?

I was looking at a UK site ebuyer and saw this.
Corsair CSM 650W Semi Modular 80+ Gold Power Supply £69.98inc. vat
 
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P

Paul

Desmond said:
Hi I have a tower unit with a 500W PSU that I think is failing. After a wile the PC crashes and I get a blue screen. This happens after it has been on for a while. On one occasion it went dead completely but it started up when I got to it.

I don't think it can be anything else. Not sure if an over heating CPU would cause the power to go off.

If it is that can I replace it with a bigger PSU 700W or 900W? is the size and foot print the same on these?

I was looking at a UK site ebuyer and saw this.
Corsair CSM 650W Semi Modular 80+ Gold Power Supply £69.98inc. vat

An overheating CPU can turn off the power.
That feature is called THERMTRIP, and exists on
modern Intel and AMD processors.

An overheating PSU can turn off the power as well.
A thermistor on one of the heatsinks inside the
PSU, keeps track of whether the PSU is properly
cooled at the moment.

A PSU even has a mains fuse inside it, but that
hardly ever blows open circuit.

A PSU can have weak output, to cause the computer
to crash. I have a PSU in my junk room here, which
can only provide 100mA on the 12V rail, before the
voltage level starts to drop to a low level. And
the PSU continues to run, and does not shut off
(because it's and old PSU, and has few forms of
protection).

A computer can crash, if the CPU overheats, but that's
more likely to happen on systems without THERMTRIP
and throttling as forms of protection.

You can replace the PSU if you like, with no guarantee
that's the only problem.

You can measure CPU temperature with various
utilities. Speedfan (almico.com) or Asus Probe perhaps.

If I suspect a power supply problem, I use a multimeter
for some voltage readings. And see if the voltage
is stable or not. I also use a clamp-on DC ammeter,
in case I suspect there is a partial short in the
motherboard. Clamp-on DC ammeters aren't all that
cheap. But a regular multimeter (for voltage readings)
is only $20.

Even without a lot of instrumentation, you can
feel the exhaust air temperature on the PSU, to
get some indication of how much load might be present.
On some PSUs that failed here, I got some initial warning,
by noting a "wobble" in the fan speed. The fan speed
goes up and down a little bit, unlike how the PSU
used to work when it was new (fan speed was very stable).
So you can also make those kinds of observations if you
like (if you cannot afford a lot of fancy instruments).

Paul
 
J

John Doe

Desmond said:
Hi I have a tower unit with a 500W PSU that I think is failing.
After a wile the PC crashes and I get a blue screen. This
happens after it has been on for a while. On one occasion it
went dead completely but it started up when I got to it.

I don't think it can be anything else. Not sure if an over
heating CPU would cause the power to go off.

You can measure both while within Windows....
 
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L

Loren Pechtel

Hi I have a tower unit with a 500W PSU that I think is failing. After a wile the PC crashes and I get a blue screen. This happens after it has been on for a while. On one occasion it went dead completely but it started up when I got to it.

I don't think it can be anything else. Not sure if an over heating CPU would cause the power to go off.

If it is that can I replace it with a bigger PSU 700W or 900W? is the size and foot print the same on these?

I was looking at a UK site ebuyer and saw this.
Corsair CSM 650W Semi Modular 80+ Gold Power Supply £69.98inc. vat

Before buying anything I would look at the cooling fan on the CPU. A
common cause of machines suddenly shutting off after they have been
operating for a while is some thermal sensor tripping.

I have never had a failing power supply that caused problems only
after the machine had been running for a while although I could
imagine that happening when you play a game and the graphics card draw
shoots up. Other than that an iffy power supply will usually trip
during the startup surge. If the voltage goes out of spec the machine
will instantly shut down--it's much better to crash the machine than
to have it act erratically. (This is why in the old days you were
supposed to take the floppy disks out of a machine before shutting it
down. The electronics didn't have a failsafe back then, the drive
could execute bogus commands as the power died. If the drive were
spinning when that happened and the command was a write....
 

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