Power Supply Question

[Dan Maguire]

The power supply fan died in my Dell 8100 Dimension today. Went to CompUSA
and bought an Antec TruePower 330. Got it home to discover that the
original Dell has two cables going to the motherboard - one a 24 pin (P1)
and the other a 16 pin (p2) connector (although not all pins are filled on
either cable.)

The Antec only has one 24 pin cable - is that OK? - i.e. do I need a power
supply with both cables??

Thanks in advance

Dan Maguire

 

[ric]

The power supply fan died in my Dell 8100 Dimension today. Went to CompUSA
and bought an Antec TruePower 330. Got it home to discover that the
original Dell has two cables going to the motherboard - one a 24 pin (P1)
and the other a 16 pin (p2) connector (although not all pins are filled on
either cable.)

The Antec only has one 24 pin cable - is that OK? - i.e. do I need a power
supply with both cables??

The original Dell PSU is probably proprietary. Why not just replace
its fan?

 

[Dave C.]

The original Dell PSU is probably proprietary. Why not just replace
its fan?

And if you tell people not to buy Dell, you get flamed. Go figure. -Dave

 

[Matt]

The power supply fan died in my Dell 8100 Dimension today. Went to CompUSA
and bought an Antec TruePower 330. Got it home to discover that the
original Dell has two cables going to the motherboard - one a 24 pin (P1)
and the other a 16 pin (p2) connector (although not all pins are filled on
either cable.)

The Antec only has one 24 pin cable - is that OK? - i.e. do I need a power
supply with both cables??

Nah, Dell does that just to confuse people. Really neither cable is
necessary. Just install your new PSU and go with it. You don't have to
bother hooking up the cables.

If you are really anal, you can find an aftermarket PSU with the same
cabling as your 8100. pcpowerandcooling.com comes to mind, but I could
be wrong about that.

But as the other poster indicated, if your old unit is still working,
you could just replace the fan. Order one that is 12V and of the same
physical size as your old one. Search newegg.com for "case fan". You
will need a soldering iron.

 

[jeffc]

And if you tell people not to buy Dell, you get flamed. Go figure. -Dave

And neither one of you know if the PSU is proprietary or not, and whether or
not they are still making them the same way. Go figure.

 

[Dave C.]

And if you tell people not to buy Dell, you get flamed. Go
igure. -Dave

And neither one of you know if the PSU is proprietary or not, and whether or
not they are still making them the same way. Go figure.

I can't think of a non-proprietary power supply that would have 24-pin and
16-pin connectors going to a motherboard. -Dave

 

[Matt]

The power supply fan died in my Dell 8100 Dimension today. Went to CompUSA
and bought an Antec TruePower 330. Got it home to discover that the
original Dell has two cables going to the motherboard - one a 24 pin (P1)
and the other a 16 pin (p2) connector (although not all pins are filled on
either cable.)

The Antec only has one 24 pin cable - is that OK? - i.e. do I need a power
supply with both cables??

I don't know why it wouldn't work to cut the cables off both PSUs, then
splice the old cable with its old connectors onto the new PSU, matching
color for color. It would be neater if you can remove the wires from
the molex connectors and insert the new wires into the old molex
connectors, matching the color pattern of the old PSU. If I were to do
this I would remove the RAM and CPU and everything else from the mobo
before applying power the first time, then check for smoke and
meltdowns. Proceed at your own risk ...

Question: If a PSU has more than one wire of the same nominal voltage,
does it hurt anything for those wires to be connected? Maybe they are
the outputs of more than one regulator and are slightly different
voltages, so that the regulators would be fighting each other?

Question: Have you contacted Dell about getting a repair or replacement?

 

[BarryNL]

I don't know why it wouldn't work to cut the cables off both PSUs, then
splice the old cable with its old connectors onto the new PSU, matching
color for color.

If the PSU and connectors are propriatary its probably not safe to
assume that the wire colours are standard either - especially given that
the consequences of getting it wrong are probably a fried computer.

Question: If a PSU has more than one wire of the same nominal voltage,
does it hurt anything for those wires to be connected? Maybe they are
the outputs of more than one regulator and are slightly different
voltages, so that the regulators would be fighting each other?

Hmm, I can see a potential problem. Say, for example, you had two 5V
lines, one rated for 10A and the other for 2A. Now connect them together
and put on a load which tries to draw 6A - you are now overloading the
2A line which has to try and supply half the current.

 

[w_tom]

Failure of two supplies in parallel, even if identical,
should be expected. Even if using two 5 amp supplies, one
(whichever has higher voltage) tries to provide the entire
load. Then the supply enters foldback current limiting; a
protection mode where voltage and current are limited. And so
the other supply attempts to pick up this load. It too
becomes overloaded and enters foldback current limiting. Now
neither supply can provide sufficient current.

Perkin Elmer did this kludge with their first 32 bit
semiconductor memory based mini computer. Apparently, load
estimates were too small. So two supplies were installed in
parallel. A careful adjustment of both supplies, somewhat
designed to work in parallel, was performed. Even then,
sometimes the supplies still failed - and another manual
adjustment of each supply was necessary.

If given enough time over temperature range, then one could
get both supplies so close as to work in parallel - as long as
room temperature remained relatively constant. Only supplies
designed for parallel operation will be sufficiently
reliable. No hardware damage occurs. Just that both supplies
can respond by entering a protective state; cause computer
shutdown.

 

[Matt]

Failure of two supplies in parallel, even if identical,
should be expected. Even if using two 5 amp supplies, one
(whichever has higher voltage) tries to provide the entire
load. Then the supply enters foldback current limiting; a
protection mode where voltage and current are limited. And so
the other supply attempts to pick up this load. It too
becomes overloaded and enters foldback current limiting. Now
neither supply can provide sufficient current.

Perkin Elmer did this kludge with their first 32 bit
semiconductor memory based mini computer. Apparently, load
estimates were too small. So two supplies were installed in
parallel. A careful adjustment of both supplies, somewhat
designed to work in parallel, was performed. Even then,
sometimes the supplies still failed - and another manual
adjustment of each supply was necessary.

If given enough time over temperature range, then one could
get both supplies so close as to work in parallel - as long as
room temperature remained relatively constant. Only supplies
designed for parallel operation will be sufficiently
reliable. No hardware damage occurs. Just that both supplies
can respond by entering a protective state; cause computer
shutdown.

Then my next question is whether there is inside the ordinary ATX
supplies of today more than one supply for a given nominal voltage. For
instance, there is more than one five volt wire coming out of an ATX
PSU. How would I tell whether these come from separate supplies (can I
use the term "separate regulators"?) inside the PSU? Could I just
measure the voltage across two such wires when they are under moderate
load, and if it stays near zero assume that they come from the same
regulator? Or maybe I could just open the box and look at where the
wires come from.

This bears on the question of whether the OP can just permute the
connections between his standard PSU and his non-standard motherboard.

 

[ric]

Then my next question is whether there is inside the ordinary ATX
supplies of today more than one supply for a given nominal voltage. For
instance, there is more than one five volt wire coming out of an ATX
PSU. How would I tell whether these come from separate supplies (can I
use the term "separate regulators"?) inside the PSU?

Wires that are the same color are terminated at the same spot in the
standard ATX PSU. For instance, all red wires are from the same +5v
output in the PSU. The +5vsb wire (different circuit) is a different
color.