Power Supply Issues

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James Whitehead

What would be the symptoms of a overloaded powersupply?

I have a 550W unit, that when I plug in a SCSI tape drive makes one of the
HDD's flash repeatly every few seconds and the drive is not recognised in
the bios. When I unplug the tape drive the HDD works fine.

I have tried it on several different PSU connections. It also does the same
when I plug a extra HDD in instead of the tape unit.

I do have many HDD's plugged into the PSU but I do not know what the
symptoms would be.
 
James Whitehead said:
What would be the symptoms of a overloaded powersupply?

I have a 550W unit, that when I plug in a SCSI tape drive makes one of the
HDD's flash repeatly every few seconds and the drive is not recognised in
the bios. When I unplug the tape drive the HDD works fine.

I have tried it on several different PSU connections. It also does the same
when I plug a extra HDD in instead of the tape unit.

I do have many HDD's plugged into the PSU but I do not know what the
symptoms would be.
Click to expand...

42 hard drives would be a problem for most power supplies, but could also
cause problems with routing cables or cooling your chassis...

....more detaills are needed.
 
42 hard drives would be a problem for most power supplies, but could also
cause problems with routing cables or cooling your chassis...

...more detaills are needed.
Click to expand...

I'll second that, MORE details needed.

Is your power supply generic? If so, odds are extremely high that it
isn't really a 550W unit. When you "plug in" that drive or another, do
you mean only plugging it into the power supply connector or also the
data cable? If you mean data cable too, see what happens with only power
connected.

The standard approach to this would be taking a multimeter and checking
voltage on 5V and 12V at a connector. Not only when system is on but
during that inital period when it's being turned on, as that's when the
12V takes a major load with all the hard drives spinning up.
 
James said:
What would be the symptoms of a overloaded powersupply?

I have a 550W unit, that when I plug in a SCSI tape drive makes one of the
HDD's flash repeatly every few seconds and the drive is not recognised in
the bios. When I unplug the tape drive the HDD works fine.

I have tried it on several different PSU connections. It also does the same
when I plug a extra HDD in instead of the tape unit.

I do have many HDD's plugged into the PSU but I do not know what the
symptoms would be.
Click to expand...

The fact that your PSU is a "550W unit" means nothing. What current is
the +12v rated at? What is the voltage on the +12v when your troubles
occur? What OS are you using.

[Wait until the 64 bit OS systems become popular. Drive non recognition
will be commonplace due to +12v tolerance violations.]
 
Ok here is the system:

Dual PIII, 5 SCSI HDD, 6 IDE HDD, 1 SCSI Tape, 1 SCSI pci, 2xIDE raid
controllers, network card video.
PSU is a ANTEC True Control 550W

The unit has adjustable 5v and 12v output. The more load you put on though
does that mean the more the 12v levels would drop?
 
The symptoms you're getting indicate an underpowered/unstable power supply
unit. The odds are its a cheap power supply price wise and does not
actually put out anywhere near 550 Watts continuously in a real world load.
I would invest in a 550 Watt Antec Tru Power power supply unit which is
conservatively rated.
 
James Whitehead said:
What would be the symptoms of a overloaded powersupply?

I have a 550W unit, that when I plug in a SCSI tape drive makes one of the
HDD's flash repeatly every few seconds and the drive is not recognised in
the bios. When I unplug the tape drive the HDD works fine.

I have tried it on several different PSU connections. It also does the same
when I plug a extra HDD in instead of the tape unit.

I do have many HDD's plugged into the PSU but I do not know what the
symptoms would be.
Click to expand...
Is there any chance at all that you might have gotten the SCSI addressing or
termination wrong? You don't say if the tape drive is every recongnized
under any circumstances. If it is a simple PS overload problem disconnecting
several of the IDE drives and then re-connecting the tape drive would
probably yield some useful information. I suggest the IDEs rather than the
SCSIs since, if it is not simply a PS problem, you will want to have all of
he SCSI devices present and accounted for to make it plain. Oh yeah, the
fact that it is just one SCSI drive has this symptom seems rather
peculiar -- if the +12 line was being overloaded and going flat then I'd
expect more symptoms than that.
 
Dave,
I have an Antec True Control 550

DaveW said:
The symptoms you're getting indicate an underpowered/unstable power supply
unit. The odds are its a cheap power supply price wise and does not
actually put out anywhere near 550 Watts continuously in a real world load.
I would invest in a 550 Watt Antec Tru Power power supply unit which is
conservatively rated.
Click to expand...
 
The tape works fine but it seems if I plug in any extra device then one of
the HDD's starts flashing.

I think I might have to get the multimeter out.
 
What would be the symptoms of a overloaded powersupply?

I have a 550W unit, that when I plug in a SCSI tape drive makes one of the
HDD's flash repeatly every few seconds
Click to expand...

Hard drives don't flash.
and the drive is not recognised in
the bios.
Click to expand...

WHICH drive isn't recognized in the BIOS?

When I unplug the tape drive the HDD works fine.
Click to expand...

How are you installing it? Which controller?...how, on the cable?
How are your jumpers set?...when you do the IDE install.
I have tried it on several different PSU connections. It also does the same
when I plug a extra HDD in instead of the tape unit.
Click to expand...

How many drives do you have installed at any one time? How many
controllers are you running?

We really need a DETAILED description of your setup...not just how
many drives you have.
I do have many HDD's plugged into the PSU but I do not know what the
symptoms would be.
Click to expand...

At this point, it doesn't sound like a PS problem. But you didn't
mention the CPU yer usin', either.


Have a nice week...

Trent©

Follow Joan Rivers' example --- get pre-embalmed!
 
OK just tested the voltages

11.46 and 4.6 is that too low?
Click to expand...


Although technically within the spec for 12V, it's still too low in
reality, and 4.6V is outside the spec.

I suggest adding 2nd PSU to power 2/3 of the drives. That many drives
puts your system more into a server class, essentially needing better than
a PC, PS/2 sized power supply else more than one... Even if you found a
manufacturer that managed to shoehorn the components into a PS/2 sized
casing to power all your devices (like PCPower & Cooling) it's still an
awefully high _realized_ power density for a PS/2 sized PSU. Given that
both rails are sagging you should have over 400W load if the PSU where
working properly, which doesn't really make much sense given you don't
have THAT many drives, but still, the alternative might be that the PSU is
failing due to being pushed to high capacity and running hot... at 400W
output you would've had roughly 170W internal heat!
 
kony said:
Although technically within the spec for 12V, it's still too low in
reality, and 4.6V is outside the spec.
Click to expand...

Adjust them up to spec. You said it's an Antec True-Control right?
 
Adjust them up to spec. You said it's an Antec True-Control right?
Click to expand...

May not be that simple if it's due to progressive failure or overloading.

While it's within it's wattage capability, it could be adjusted to provide
that wattage as more volts but fewer amps, but when the amperage drain at
a fixed voltage causes that voltage to drop, the power supply is typically
at it's limits and although it may work in that situation, it's not a good
idea, may be quite hot running and a bit of ripple.
 
kony said:
May not be that simple if it's due to progressive failure or
overloading.

While it's within it's wattage capability, it could be adjusted to
provide that wattage as more volts but fewer amps, but when the
amperage drain at a fixed voltage causes that voltage to drop, the
power supply is typically at it's limits and although it may work in
that situation, it's not a good idea, may be quite hot running and a
bit of ripple.
Click to expand...

Good point, as usual. :-)
 
James Whitehead said:
What would be the symptoms of a overloaded powersupply?

I have a 550W unit, that when I plug in a SCSI tape drive makes one of the
HDD's flash repeatly every few seconds and the drive is not recognised in
the bios. When I unplug the tape drive the HDD works fine.

I have tried it on several different PSU connections. It also does the same
when I plug a extra HDD in instead of the tape unit.

I do have many HDD's plugged into the PSU but I do not know what the
symptoms would be.
Click to expand...

My PSU if 90W and I have 2 harddrives, as CDr/w and a cdrom.
Does your PSU function as a part of your central heating system?
 
James Whitehead said:
Dual PIII, 5 SCSI HDD, 6 IDE HDD, 1 SCSI Tape, 1 SCSI pci,
2xIDE raid controllers, network card video. PSU is a
ANTEC True Control 550W
Click to expand...

What happens when you remove some of the HDDs? If that improves
matters, then your power supply is inadequate, not necessarily because
your system consumes more than 550W but because it may be drawing too
much power at one particular voltage, very likely +12V. Also high
performance video cards can draw a great deal of power from the +5V
(this and dual CPUs could overload the Antec's +5V) or +12V.
What would be the symptoms of a overloaded powersupply?
Click to expand...

Abnormally low voltages at the power connectors that are used, and in
the case of a Truepower that would mean anything more than 3% below
nominal values. Measure with a meter, not through the computer, which
isn't accurate enough, and measure during start-up because disk drives
can draw 2-3 amps from the +12V during the first few seconds (drive
start-up is staggered for this reason, and SCSI controllers often let
you configure this).

I strongly suggest you find how much power your system draws from each
voltage line. Don't simply use a power estimator because even the
best (posibly the one at http://takaman.jp) often give wildly
incorrect readings. Instead buy or borrow a clamp-on DC ammeter and
take measurements, but beware that most clamp-on meters measure only
AC, not DC.

It's possible you need a second power supply for some of the disk
drives.
 
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