+5VSB fluctuations

  • Thread starter Thread starter spodosaurus
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spodosaurus

Hi all,

Are fluctuations in the +5VSB from my Antec TruePower PSU anything to
worry about? I have a system that's been blue screening and restarting
which after restart claims there's been a driver error (WinXP Home OS),
yet no driver is ever specified and all drivers are up to date or have
been brought up to date. The voltage ranges from 5.1 to 5.6V on the
+5VSB line.


The only other oddity was the +5V rail was only at 4.8V (I was using a
PSU tester to quickly go through several systems, so I need to go back
to this one and confirm if it really is 4.8V or if it's 4.76 or 4.84V.

TIA,

Ari


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Many people around the world are waiting for a marrow transplant. Please
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spodosaurus said:
Hi all,

Are fluctuations in the +5VSB from my Antec TruePower PSU anything to
worry about? I have a system that's been blue screening and restarting
which after restart claims there's been a driver error (WinXP Home OS),
yet no driver is ever specified and all drivers are up to date or have
been brought up to date. The voltage ranges from 5.1 to 5.6V on the
+5VSB line.


The only other oddity was the +5V rail was only at 4.8V (I was using a
PSU tester to quickly go through several systems, so I need to go back
to this one and confirm if it really is 4.8V or if it's 4.76 or 4.84V.

TIA,

Ari
Click to expand...

The spec limits are +/- 5% and should be tighter than that, if things
were working right.

The resistance to voltage varies amongst devices. In years past, the
input on some TTL devices, could take up to 7V. Devices now are not
as resistant to extremes. 5V tolerance is something that is hard
to do,when all the "normal" voltages on a chip, are so much lower.

I would recheck the voltages with a multimeter, and replace the supply
if the measured deviations are as large as you are seeing at the moment.
You might not have blown anything, but what will the PSU do tomorrow
or the day after ?

Paul
 
Hi all,

Are fluctuations in the +5VSB from my Antec TruePower PSU anything to
worry about? I have a system that's been blue screening and restarting
which after restart claims there's been a driver error (WinXP Home OS),
yet no driver is ever specified and all drivers are up to date or have
been brought up to date. The voltage ranges from 5.1 to 5.6V on the
+5VSB line.
Click to expand...

I can't understand why the +5VSB rail would fluctuate so much unless
there was a genuine fault. AFAICT, this rail is usually generated and
regulated independently of all the others, often (usually?) by means
of a linear 3-terminal regulator IC.

I believe this example may be typical:
http://www.pavouk.org/hw/en_mxr-250p.html

Depending on the design, I'd look for a small, dried out or bulging
electrolytic cap on the AC side.
The only other oddity was the +5V rail was only at 4.8V (I was using a
PSU tester to quickly go through several systems, so I need to go back
to this one and confirm if it really is 4.8V or if it's 4.76 or 4.84V.

TIA,

Ari
Click to expand...

You need to look at the +12V and +5V rails as a pair. I don't know
about TruePower, but many supplies, including my 300W Antec, appear to
regulate by calculating a weighted average of these two rails. So if
the +12V rail rises, then the +5V rail drops to compensate. I don't
know how you're testing your supply, but try adding a load to the +12V
output.

- Franc Zabkar
 
Franc said:
You need to look at the +12V and +5V rails as a pair. I don't know
about TruePower, but many supplies, including my 300W Antec, appear to
regulate by calculating a weighted average of these two rails. So if
the +12V rail rises, then the +5V rail drops to compensate. I don't
know how you're testing your supply, but try adding a load to the +12V
output.

- Franc Zabkar
Click to expand...

The PSU tester is connected to the 20pin and 4pin connectors, and the
PSU powers on with the computer case switch via the motherboard. Hard
drives, floppy drive, and optical drive spin up, so there is a load. 12V
rails are steady. The 5V rail from the 20pin connector is steady at 4.8V
(will test with a multimeter to get the last digit). Once a system is
powered on, can fluctuations in the 5VSB line account for blue screens
and reboots?

Ari


--
spammage trappage: remove the underscores to reply
Many people around the world are waiting for a marrow transplant. Please
volunteer to be a marrow donor and literally save someone's life:
http://www.abmdr.org.au/
http://www.marrow.org/
 
Paul said:
The spec limits are +/- 5% and should be tighter than that, if things
were working right.

The resistance to voltage varies amongst devices. In years past, the
input on some TTL devices, could take up to 7V. Devices now are not
as resistant to extremes. 5V tolerance is something that is hard
to do,when all the "normal" voltages on a chip, are so much lower.

I would recheck the voltages with a multimeter, and replace the supply
if the measured deviations are as large as you are seeing at the moment.
You might not have blown anything, but what will the PSU do tomorrow
or the day after ?

Paul
Click to expand...

Well, the Power Supply Tester reported bad rails as good and the good
rail (+5VSB) as bad, and most of the other voltages as way outside what
my multimeter reported (multimeter is known good)! I just got the power
supply tester and have emailed the etailer about returning it. I needed
a quick way to test PSUs to rule them out as the cause of the problem,
but this thing is only as good as a paperclip to get the PC to power on!

On the 20 pin ATX connector:

Pins 1, 2, and 11 (3.3V): 3.28V (good)
Pins 4, 6, 19, and 20 (5V): 4.68V (bad)
Pin 9 (5VSB): 5.05V steady (good)
Pin 10 (12V): 11.66V (good)
Pin 12 (-12V): -12.58V (good)

It's just a tad over two years old, and I'm wondering if the buldging
capacitors on the old Gigabyte GA-7VTXE+ motherboard it's powering have
had something to do with its early demise? (I've lost three Gigabyte
boards to these)

Ari

--
spammage trappage: remove the underscores to reply
Many people around the world are waiting for a marrow transplant. Please
volunteer to be a marrow donor and literally save someone's life:
http://www.abmdr.org.au/
http://www.marrow.org/
 
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