Bestec ATX-300-12Z 24>20pin - Pink wire

[socketa]

Hi all,

Decided to buy a half decent (well, at least, not bottom of the barrell) PSU.
It's going onto a motherboard with only a 20-pin power socket.
This bestec has a 24-pin plug that can not be seperated into a 20+4 pin.
The plug wont fit into the socket because there are components in the way.
I had unclipped (with the eye of a needle) and removed all of the pins from another 20+4 pin plug, and was going to transfer the bestec wires over into this empty plug, untill i noticed a pink wire doubled up with a red wire, on pin 23.
I read, in another thread, that this is a sensor wire.
If i replaced the wires to exaclty the same positions, then this pink wire (which would now be in the 4-pin plug) would wind up not being used.
Is that OK?

Or would it be preferable to swap this terminal (with the pink and red wire) with one of the other 5V terminals on the new 20-pin plug, so that the 5V rail is still regulated?
If so, which one, and why?

Or is this PSU only compatible with motherboards that have 24-pin sockets?

[c_hegge]

Re: Bestec ATX-300-12Z 24>20pin - Pink wire

It would work fine. 24 pin is just 20 pin with another 4 pins added to the side. That extra wire is indeed just a sensor. many PSUs have that so that the secondary controller IC can see what the voltage is doing at the motherboard end.

I would pop the cover on that PSU and check the capacitors in it, though. Bestecs do sometimes get bad caps (particularly on the 5vsb rail).

[socketa]

Re: Bestec ATX-300-12Z 24>20pin - Pink wire

So wouldn't the PSU work better if the red/pink terminal was swapped with a red wire on the replacement 20-pin connector?
Because, if the pink wire is not connected, then there is no information going to the sensor circuit/IC - so it can't adjust voltage requirements for the 5V rail.
Wouldn't the PSU work better (or more efficiently) if it was getting some info back on the sensor wire?
i.e., if this sensor wire was actually being utilized

What does the 5V wire on the 4-pin connector supply voltage to?
Is it sensible to swap the red/pink (both wires are crimped together on the same terminal) with a red one on the 20-pin connector,
since, after moving the terminals from one connector to the other, it would otherwise wind up not being used?

If so, which one should i swap it with? - i.e., i don't know what each 5v pin does on the motherboard connector,
There would be 4 positions to choose from.

[kc8adu]

Re: Bestec ATX-300-12Z 24>20pin - Pink wire

its +5 remote sense.
just include it in your 20 pin mod and eliminate one of the others.
oh and recap!

[socketa]

Re: Bestec ATX-300-12Z 24>20pin - Pink wire

The caps look OK - although there is a component-type odor coming from it.
Will test voltages after i get this plug sorted - want to make sure that the PSU working, before buying caps for it.

Was just wondering why the sensor wire was on that particular pin - was it completely arbitrary?, or was there some reason for it?
i.e., would have that being the pin that demanded the most power, like the CPU or one of the chipset processors?

Just checked continuity of all the 5v positions on a 24-pin motherboard, and they all appear to be connected together.

If they are all connected on a 5v rail on the motherboard, then what is the point of having 4 (in the case of 20-pin connector) or 5 (in the case of 24-pin connector) 5v wires coming from the PSU, instead of just one 5v wire?

[Per Hansson]

Re: Bestec ATX-300-12Z 24>20pin - Pink wire

Was just wondering why the sensor wire was on that particular pin - was it completely arbitrary?, or was there some reason for it?
i.e., would have that being the pin that demanded the most power, like the CPU or one of the chipset processors?

It's the pin where you are likely to have the highest current draw, all pretty academic though.

Just checked continuity of all the 5V positions on a 24-pin motherboard, and they all appear to be connected together.

Yup, that's how they are made

If they are all connected on a 5v rail on the motherboard, then what is the point of having 4 (in the case of 20-pin connector) or 5 (in the case of 24-pin connector) 5v wires coming from the PSU, instead of just one 5v wire?

Because the pins in the ATX connector can only handle so much current, same goes for the wires.
The reason the extra 4 pins where added was because otherwise you would get problems with burning or charring of the ATX connector, because too much current was going through the pins...

[socketa]

Re: Bestec ATX-300-12Z 24>20pin - Pink wire

Thanks,
The voltage drop/current rating of the wire did cross my mind.

One more point to clear up:

It's the pin where you are likely to have the highest current draw, all pretty academic though.

If all the 5v wires are all the same, and also connected together on the same rail on the motherboard, how can one wire have a greater current draw than the others.

[chozo4]

Re: Bestec ATX-300-12Z 24>20pin - Pink wire

Thanks,
The voltage drop/current rating of the wire did cross my mind.

One more point to clear up:



If all the 5v wires are all the same, and also connected together on the same rail on the motherboard, how can one wire have a greater current draw than the others.

That's actually the reason for the extra wires. Essentially all it's doing is dividing the current between the wires to keep within ATX wire gauge specifications and avoid heat buildup while reducing wire resistance. In turn it also reduces the effect of a voltage crop over the wires itself, again, due to less resistance as well. In this case one wire cannot draw more than the others unless the lengths or wire conditions (poorer solder joint, looser crimp on the connecting pin, etc) are slightly different but it's negligible at best due to less than an ohm resistance difference.

Though, as an alternative one can do the math and simply decrease most of the common connected wires to a thicker gauge and remove the extra's altogether. The only issue then is the amount of current the connector pins can handle. As an alternative in THAT case would be to combine them into a single thick wire and at the plug end divide it into the smaller wires between the pins thus reducing overall wire clutter. All you lose then is wire flexibility overall however.

[socketa]

Re: Bestec ATX-300-12Z 24>20pin - Pink wire

Yep, i get that thanks

But what i dont get is this:

Originally Posted by socketa
Was just wondering why the sensor wire was on that particular pin - was it completely arbitrary?, or was there some reason for it?
i.e., would have that being the pin that demanded the most power, like the CPU or one of the chipset processors?

It's the pin where you are likely to have the highest current draw, all pretty academic though.

If there is multiple pins for red wires, and they are all connected together on the motherboard, then how can one have a higher current draw than any of the others?
The selection of which red wire to connect the sensor wire to would have to be completey abitrary, wouldn't it?