Asus A7V-ML Again

[Dajan]

Thanks to rob for previous info, the reason I got the Pavillion 7909 for
free is that the power supply died and a new one was going to cost its
previous owner upwards of £80.00, so he gave it to me, I have an old power
supply unit but it does not have the 3 pin cable for the PS FAN connection
on the board which I think runs the 2 fans, cpu & case, my question is can I
just power the 12v & ground on the board and leave the rotational one
disconnected, or do you need the rotational one connecting.

Cheers

 

[Paul]

Thanks to rob for previous info, the reason I got the Pavillion 7909 for
free is that the power supply died and a new one was going to cost its
previous owner upwards of £80.00, so he gave it to me, I have an old power
supply unit but it does not have the 3 pin cable for the PS FAN connection
on the board which I think runs the 2 fans, cpu & case, my question is can I
just power the 12v & ground on the board and leave the rotational one
disconnected, or do you need the rotational one connecting.

Cheers

See page 35 here. The three fan headers are outputs. They
all have +12V on them.

http://www.asus.com/pub/ASUS/mb/socka/kt133/a7v-m/a7vm-101.pdf

A power supply that has monitoring on it, can have two kinds of
monitoring. A power supply with a two wire cable, but a three pin
connector, is meant for RPM monitoring. The two wires on the
cable are Rotation and GND. In extreme cases, it is possible for
only one wire to be used - Rotation - because the ground is
already established through the power cabling to the PSU.

The second monitoring type, consists of two wires but a two
pin header. This is a thermistor temperature monitor cable and
should not be connected to a fan header (it doesn't even match,
so it should be obvious it doesn't go on a fan header). The
thermistor allows a motherboard equipped with a thermal monitor
input, to tell you what the internal temperature of the power
supply is. I don't see one on the A7V-M.

I notice in the picture of the BIOS screens in the manual, that
the PSU header rotation signal is not monitored. I guess that means
the PSU header on the motherboard, could be used to connect a
chassis exhaust fan (one of those fans that doesn't have a
rotation signal on the cable). And then the chassis header can be
used for any fan that has the rotation signal, even a PSU rotation
monitor cable.

Not everything Asus does makes sense.

Just a guess,
Paul

 

[Dajan]

Thanks Paul
The 3 fan headers are not all outputs, I actually took the old power supply
unit out and there was a 3 pin lead from the unit to the PS FAN header, the
cpu lead is connected to the cpu header and the chassis fan is connected to
the other header which to me means the power from the power supply goes to
the the PS FAN header input which then feeds the other 2

 

[Paul]

Thanks Paul
The 3 fan headers are not all outputs, I actually took the old power supply
unit out and there was a 3 pin lead from the unit to the PS FAN header, the
cpu lead is connected to the cpu header and the chassis fan is connected to
the other header which to me means the power from the power supply goes to
the the PS FAN header input which then feeds the other 2

This is how the fan power works on my P4C800-E, as measured with
an ohmmeter. The CPU fan measures open circuit, implying the MOSFET
located next to the header, is the culprit.

ATX20pin_+12V ---------+----------+-------- ------------+
| | | | |
| | ------ |
PSU Chassis | CPU
Fan Fan MOSFET Fan
+12V +12V for Q-fan +12V

Your board likely looks like this, as I don't see Q-fan in
the manual. The reason there is +12V on the PSU connector, is
if you want to connect a chassis fan to it. A PSU fan should
be getting its juice from inside the PSU, and only the rotation
and GND should be connected via the PSU fan monitor cable.

ATX20pin_+12V ---------+----------+---------------+
| | |
| | |
PSU Chassis CPU
Fan Fan Fan
+12V +12V +12V

Using an ohmmeter, measure from the +12V pin on the 20 pin
motherboard connector, to the fan headers. If there is an
open circuit, then your theory, shown below, would be correct

ATX20pin_+12V - --+----------+---------------+
^ | | |
| | | |
no connection ? -+ PSU Chassis CPU
Fan Fan Fan
+12V +12V +12V

ATX connector pinouts are on page 29 of this doc. You are looking
into the ends of the power supply in that figure, so apply the
correct transformation when viewing the connector on the mobo.

http://www.formfactors.org/developer/specs/atx/ATX12V_1_3dg.pdf

If, in fact, there is continuity from ATX20pin_+12V
to the fan headers, there is no need for power to flow out
of the PSU fan wire, to the other fan headers. It would
be a redundant connection, and a dangerous one at that,
as more than one amp could flow down the PSU fan cable to
the motherboard, and that is not a good idea. I think the
fan header connectors aren't rated for more than about
an amp. And that is why the PSU fan cable should only use
two wires, so there is no sneak path for the +12V to flow
via the third wire. The motherboard +12V current should flow
through the power path via pin 10 on the ATX power connector,
as that pin and wire can handle 6 amps.

HTH,
Paul

 

[Paul]

Thanks Paul
The 3 fan headers are not all outputs, I actually took the old power supply
unit out and there was a 3 pin lead from the unit to the PS FAN header, the
cpu lead is connected to the cpu header and the chassis fan is connected to
the other header which to me means the power from the power supply goes to
the the PS FAN header input which then feeds the other 2

The only other evidence I have to offer, is your PSU fan cable is
not part of the ATX power supply standard.

http://www.formfactors.org/developer/specs/atx/ATX12V_1_3dg.pdf

And, that means a standards compliant power supply would not be
able to make the fans run, if your theory was correct. Asus
wouldn't do something like that. The motherboard has to work
with any power supply meeting the ATX standard, and capable of
supplying the necessary load current.

It is indirect evidence, but the only other way I can think of
to convince you.

Paul

 

[Dajan]

When the person took the power supply unit to the computer shop for a
replacement he was told that the type he had with a 3 pin connector was a
special one and would cost over £80.00, unusual as the are nomally £15.00,
the 3 core lead definately went from the unit, (which incidently is smaller
than a normal unit and fitted inside a housing to make it fit the case) to
the PS FAN header which means it must be the feed to the board which feeds
the other 2 headers

Dave

 

[Paul]

When the person took the power supply unit to the computer shop for a
replacement he was told that the type he had with a 3 pin connector was a
special one and would cost over £80.00, unusual as the are nomally £15.00,
the 3 core lead definately went from the unit, (which incidently is smaller
than a normal unit and fitted inside a housing to make it fit the case) to
the PS FAN header which means it must be the feed to the board which feeds
the other 2 headers

Dave

OK. I went to the HP site, and tunneled down to their parts site.
The Pavilion 7909 has a Bestec ATX-1956F listed as the 200W
power supply for the unit.

http://partsurfer.hp.com/cgi-bin/sp...r_id=&callingsite=&strsrch=&keysel=?&catsel=?

After an Altavista search, here is the first site I found:

http://www.affordablesurplus.com/bestec-atx-1956f-power-supply.asp

"NOTE:  Your power supply may not have all of these connectors.
In that case, the unused connectors can be tied off with no
problem. The important thing is to ensure that this unit has
at least the connectors that are connected to your motherboard
and peripherals with one exception.  If the original has a P7,
P9 or FAN/C 3 Pin connector...no problem.  The replacement unit
operates without this connector."

What that says, is the Bestec supply internal fan was remotely
controlled by the motherboard. In other words, the power supply
had a weird requirement, and not the motherboard. If you use
a standard ATX power supply as replacement, a standard ATX power
supply can control its own fan. So, a £15 PSU can be used, as long
as it has current outputs at least as good as the current numbers
listed on the side of the original power supply. The
affordablesurplus site lists these numbers on their replacement:

[email protected] 5V@21A 12V@10A [email protected] [email protected] +5Vsb@2A

Knowing how HP designs stuff, they like to have more fan control
than Asus is used to. The info on the affordablesurplus web site,
suggests this is how the Bestec works. The Bestec was getting
fan power from the motherboard, so the Asus motherboard must have
a fan control channel. Since the A7V-ML is an OEM design, Asus
can make changes like that for a big customer.

| Bestec Fan Design
|
ATX20_+12V ---- ------------x >-----+12V_fan
| | |
------ ------x <----- RPM
| | |
| v --x >----- GND
Asus fan RPM | |
Control | |
GND

If the replacement ATX power supply has no fan cable, the mother
board will not care - if the BIOS is monitoring the RPM signal,
set the BIOS to [Ignore] for the PSU fan. The PSU will decide
how fast to run the fan - when the PSU gets hot, the fan will
speed up, without any involvement from the motherboard.

| Replacement Fan Design
|
ATX20_+12V ---- ------------x -----+12V_fan
| | | | --- GND
------ ------x | |
| | | ^ ^
| v --x (Internal fan power)
Asus fan RPM | |
Control | |
GND

If the replacement ATX power supply has a fan monitor cable, it
will have two wires. The +12V to the fan will come from an
internal circuit. You could connect the fan monitor cable to
the Asus motherboard if you wanted - I should only have two
wires, as the fan power is being provided from inside the PSU.

| Replacement Fan Design
|
| -----< (Internal fan
| | power)
ATX20_+12V ---- ------------x |-+12V_fan
| | |
------ ------x <----- RPM
| | |
| v --x >----- GND
Asus fan RPM | |
Control | |
GND

So, I'm afraid your friend was getting the shaft, for that
£80 replacement.

HTH,
Paul