PSU question - confused

  • Thread starter Thread starter Glendon
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Glendon

Hi, kinda new to all this stuff. I currently want to change an old PSU
unit in a computer to a higher rated one. However when I checked the
spec of the old PSU it had a -5V output, now all the PSU I have
looked at dont have this output , so I am left a bit worried.

So will a newer PSU without a -5V work ( or if it stops some stuuf
working what? - also what exactly is the -5V used for???) or do I
have to try find a PSU with a -5V output??

Thanks,

a confused new guy!!!
 
Glendon said:
Hi, kinda new to all this stuff. I currently want to change an old PSU
unit in a computer to a higher rated one. However when I checked the
spec of the old PSU it had a -5V output, now all the PSU I have
looked at dont have this output , so I am left a bit worried.

So will a newer PSU without a -5V work ( or if it stops some stuuf
working what? - also what exactly is the -5V used for???) or do I
have to try find a PSU with a -5V output??

Thanks,

a confused new guy!!!
Click to expand...
Some old chips needed a negative supply,
newer chips ,when they need it , generate
this on-chip, so,no you dont need -5V.
 
Glendon said:
Hi, kinda new to all this stuff. I currently want to change an old PSU
unit in a computer to a higher rated one. However when I checked the
spec of the old PSU it had a -5V output, now all the PSU I have
looked at dont have this output , so I am left a bit worried.

So will a newer PSU without a -5V work ( or if it stops some stuuf
working what? - also what exactly is the -5V used for???) or do I
have to try find a PSU with a -5V output??

Thanks,

a confused new guy!!!
Click to expand...

If you give us the make and model of your motherboard, we could find
out whether or not your board requires it or not.

Many boards don't need one, but I'd hate for yours to be one that does,
and you wind up with a dead mb because of an assumption. It's unlikely
you'd damage anything, but i'd perfer to actually verify that first.
 
Sjouke said:
Some old chips needed a negative supply,
newer chips ,when they need it , generate
this on-chip, so,no you dont need -5V.
Click to expand...

If his system is older, as it seems to be, he may indeed need the -5v.
Without knowing specifics, we're just guessing.
 
UCLAN said:
Sjouke Burry wrote
Click to expand...
If his system is older, as it seems to be, he may indeed need the -5v.
Without knowing specifics, we're just guessing.
Click to expand...

Not much of a guess, I cant think of anything that
uses an ATX supply that ever used that rail.

There was bugger all even with AT supplys.
 
I have bad news guys and will proably get loads of grief for it. Its
an old Dell!!!!!!!!!!!, I have read bits and bobs that the -5V is
probably only used for the ISA slot (not used by me or anyone I
think!!!) and the onboard sound (Im guessing an old sound card
installed on an empty PCI slot would overcome this?). Im just not in
a position to buy a whole new setup and would rather just get a new
ATX PSU (which I can then use in the future) and a $5 Dell - ATX
power adapter that is available.

The main I dont want is to get smoke coming out of the machine!!!!!!!
 
Glendon said:
I have bad news guys and will proably get loads of grief for it. Its
an old Dell!!!!!!!!!!!, I have read bits and bobs that the -5V is
probably only used for the ISA slot (not used by me or anyone I
think!!!) and the onboard sound (Im guessing an old sound card
installed on an empty PCI slot would overcome this?). Im just not in
a position to buy a whole new setup and would rather just get a new
ATX PSU (which I can then use in the future) and a $5 Dell - ATX
power adapter that is available.

The main I dont want is to get smoke coming out of the machine!!!!!!!
Click to expand...

Oh, THANK you for telling us this, the p3 and P2 dells are NOT atx. It
looks like atx, but it ain't. You may be stuck with the PSU you have
got, for now. Use the converter if you really have a pressing need for
the larger PSU, such as a bunch of HDDS, or something. But there's
enough margin in the dell psu to run 2 hdds, 2, cds, and a floppy.
 
Glendon said:
I have bad news guys and will proably get loads of grief for it. Its
an old Dell!!!!!!!!!!!, I have read bits and bobs that the -5V is
probably only used for the ISA slot (not used by me or anyone I
think!!!) and the onboard sound (Im guessing an old sound card
installed on an empty PCI slot would overcome this?). Im just not in
a position to buy a whole new setup and would rather just get a new
ATX PSU (which I can then use in the future) and a $5 Dell - ATX
power adapter that is available.

The main I dont want is to get smoke coming out of the machine!!!!!!!
Click to expand...

Dell is a high volume seller, so theyre not going to specify PSUs with
a feature they dont use. Therefore it needs the -5v.

I dont know why you need another psu though, yours faulty?

Finally you can upgrade psu capability wihout replacing te psu by
adding a small 5v or regulated 12v psu to run some drives, if its
really needed.


NT
 
(e-mail address removed) wrote
Glendon wrote
Click to expand...
Dell is a high volume seller, so theyre not going to specify
PSUs with a feature they dont use. Therefore it needs the -5v.
Click to expand...

You cant assume that. Bet it doesnt use -5V, its not used for much at all.
 
Rod said:
(e-mail address removed) wrote


You cant assume that. Bet it doesnt use -5V, its not used for much at all.
Click to expand...

P3 and P2 dells have different pinouts. THAT's the problem.

THIS is Dell Special PSU
http://pinouts.ru/Power/dell_atxpower_pinout.shtml
http://pinouts.ru/Power/dell_atxaux_pinout.shtml

THIS is Standard ATX
http://pinouts.ru/Power/atxpower_pinout.shtml

You will note that dell puts 5v on pin 1, where Standard ATX uses 3.3V,
among other changes. Also, Dell has that extra 6-pin connector.

In short, WHETHER OR NOT Dell uses -5v. It's NOT compatable with ATX.
 
(e-mail address removed) wrote
Rod Speed wrote
Click to expand...
P3 and P2 dells have different pinouts. THAT's the problem.
Click to expand...

We'll see...
THIS is Dell Special PSU
http://pinouts.ru/Power/dell_atxpower_pinout.shtml
http://pinouts.ru/Power/dell_atxaux_pinout.shtml
Click to expand...
THIS is Standard ATX
http://pinouts.ru/Power/atxpower_pinout.shtml
Click to expand...

I wasnt talking about that, just the claim that there is only -5V
because its actually being used. I dont believe it is being used.
You will note that dell puts 5v on pin 1, where Standard ATX uses
3.3V, among other changes. Also, Dell has that extra 6-pin connector.
Click to expand...
In short, WHETHER OR NOT Dell uses -5v. It's NOT compatable with ATX.
Click to expand...

Not relevant for the OP, he had decided to use a standard power
supply with an adapter. He's just concerned about whether the
system will actually use -5V and so the adapter wont work since
there is no -5V rail on the supply he wants to use, with an adapter.
 
Rod said:
(e-mail address removed) wrote

You cant assume that. Bet it doesnt use -5V, its not used for much at all.
Click to expand...

I didnt assume it, fool. Logic and fact versus assumption.


NT
 
Don't pay attention to Rod Speed, the troll.


Rod said:
(e-mail address removed) wrote



We'll see...




I wasnt talking about that, just the claim that there is only -5V
because its actually being used. I dont believe it is being used.




Not relevant for the OP, he had decided to use a standard power
supply with an adapter. He's just concerned about whether the
system will actually use -5V and so the adapter wont work since
there is no -5V rail on the supply he wants to use, with an adapter.
Click to expand...
 
Dell is a high volume seller, so theyre not going to specify PSUs with
a feature they dont use. Therefore it needs the -5v.
Click to expand...

No.

Dell does not sell only one type of system, they're not
going to have custom PSUs built for every possible
configuration. It could easily be that any given system
with a PSU supporting -5V, does not actually use that -5V.


I dont know why you need another psu though, yours faulty?

Finally you can upgrade psu capability wihout replacing te psu by
adding a small 5v or regulated 12v psu to run some drives, if its
really needed.
Click to expand...

While that's possible (providing a common ground is used),
such dedicated supplies tend to cost quite as much if not
more than commodity grade ATX, even if one has to buy a Dell
adapter for it. Also, Dell had used some pretty high
quality PSU in that era, certainly enough to support adding
a drive or two... so if there were other addt'l upgrades
enough to exceed the current capability of the PSU, taking
away on the amount of current for a couple drives (which
after initial turn-on, should only be about an amp per rail)
is still quite low margin, compared to buying a typical 420W
PSU which can now be had for about $30 AR (for example
Thermaltake 420W @ newegg.com).
 
I didnt assume it, fool. Logic and fact versus assumption.
Click to expand...


Actually no, there is no basis for the presumption that a
typical Dell P2 or P3 era system uses -5V for anything.
Dell would have to also be using actual components that
needed -5V, for starters...
 
Merrill P. L. Worthington said:
Don't pay attention to Rod Speed, the troll.
Click to expand...

Will you please stop quoting his trolls in their entirety. This
serves only to impinge on those of us who have him plonked. If you
want to point out his trolling, it takes only the one line I have
quoted above. Better yet, plonk and ignore him.

--
"I'm the commander--see, I don't have to explain -- I don't need
to explain why I say things. That's the interesting thing about
being the President. Maybe somebody needs to explain to me why
they say something, but I don't feel like I owe anybody an
explanation." - George W. Bush, 2002-11-19
 
kony said:
On 4 Sep 2006 17:56:04 -0700, (e-mail address removed) wrote:
Click to expand...
No.

Dell does not sell only one type of system, they're not
going to have custom PSUs built for every possible
configuration. It could easily be that any given system
with a PSU supporting -5V, does not actually use that -5V.
Click to expand...

For low volume production, using a limited range of psus makes sense.
But when you're selling a milion of a model, using a psu tailored to
each model saves a company a fortune. And you'd be hard pressed to find
a major company unwise to such business basics. For example, say we
could save 40c by leaving out the -5 rail on a million machines...
thats $400,000. No-one thorws that much away and stays in business.

While that's possible (providing a common ground is used),
such dedicated supplies tend to cost quite as much if not
more than commodity grade ATX, even if one has to buy a Dell
adapter for it.
Click to expand...

probably. OTOH many people will have a stabilised 12v wallwart lying
around. But I'd agree the need is not that likely.


NT
 
For low volume production, using a limited range of psus makes sense.
But when you're selling a milion of a model, using a psu tailored to
each model saves a company a fortune. And you'd be hard pressed to find
a major company unwise to such business basics. For example, say we
could save 40c by leaving out the -5 rail on a million machines...
thats $400,000. No-one thorws that much away and stays in business.
Click to expand...

Untrue, it could actually cost more to omit that part if the
PSU manufacturer (which is not Dell) were already producing
the whole board for many uses instead of setting up a
separate line or entirely new design, and Dell only needed a
different wiring harness on it for their proprietary pinout
(which was the case, I have actually modified one of those
Dell PSU to power a standard ATX board).
 
(e-mail address removed) wrote
kony wrote
Click to expand...
For low volume production, using a limited range of psus
makes sense. But when you're selling a milion of a model,
using a psu tailored to each model saves a company a fortune.
Click to expand...

Fantasy with dropping the -5V rail. That would save them bugger all.
And you'd be hard pressed to find a major
company unwise to such business basics.
Click to expand...

Have fun explaining how come even
Dell NOW uses standard power supplys.
For example, say we could save 40c by leaving out the -5 rail on a million
machines...
Click to expand...

Dell doesnt move a million machines.
thats $400,000. No-one thorws that much away and stays in business.
Click to expand...

Have fun explaining how come even
Dell NOW uses standard power supplys.
 
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