No POST only FF alarm on boot

[John Smith]

I've been running an Epox MVP3C2 for a while, then I damaged a couple of SMD
componets getting the clip off the HSF. The board has been repaired (I am in
the electronics industry), and *should* be OK.
Problem is the FF alarm sounds immediately it starts to boot. I suspected it
was that I had previously set in the *BIOS* for the alarm to sound if the
CPU fan was
under a limit (if that's possible), whereas this time I am using a fan
straight off the
PSU (which is working). To trick the alarm I have fitted a couple
of separate CPU fans to the 3-pin connection for the CPU fan (also also for
the
chassis fan), but noticed neither would turn at all besides a flicker when
the on-off switch is pressed.
Does anyone know if the lack of power to the mobo fan connections is the
fault cause of the FF alarm - or the alarm is doing the opposite and cutting
the power to the mobo?
What other causes for a lack of power to the 3-pin connectors - is there a
fuse on the board anywhere?
Besides if the PSU or mobo connectors are faulty...

TIA
Keith

 

[JT]

I've been running an Epox MVP3C2 for a while, then I damaged a couple of SMD
componets getting the clip off the HSF. The board has been repaired (I am in
the electronics industry), and *should* be OK.
Problem is the FF alarm sounds immediately it starts to boot. I suspected it
was that I had previously set in the *BIOS* for the alarm to sound if the
CPU fan was
under a limit (if that's possible), whereas this time I am using a fan
straight off the
PSU (which is working). To trick the alarm I have fitted a couple
of separate CPU fans to the 3-pin connection for the CPU fan (also also for
the
chassis fan), but noticed neither would turn at all besides a flicker when
the on-off switch is pressed.
Does anyone know if the lack of power to the mobo fan connections is the
fault cause of the FF alarm - or the alarm is doing the opposite and cutting
the power to the mobo?
What other causes for a lack of power to the 3-pin connectors - is there a
fuse on the board anywhere?
Besides if the PSU or mobo connectors are faulty...

TIA
Keith

The third wire is a speed sensor, which the motherboard uses to detect a
fan not moving. You can make (or buy) an adapter that splits the fan cable
so that power comes from a PSU connector, and the speed sensor connects to
the motherboard fan connector. Sold for people that want to put big, high
current fans on CPU heatsinks. There is probably an SMD fuse or resistor
that acts like a fuse in the 12v line for the fans on the motherboard. No
telling where it actually is located.

JT

 

[John Smith]

The third wire is a speed sensor, which the motherboard uses to detect a
fan not moving. You can make (or buy) an adapter that splits the fan cable
so that power comes from a PSU connector, and the speed sensor connects to
the motherboard fan connector. Sold for people that want to put big, high
current fans on CPU heatsinks. There is probably an SMD fuse or resistor
that acts like a fuse in the 12v line for the fans on the motherboard. No
telling where it actually is located.

JT

Thanks JT, yep we're thinking along the same lines now - the one damaged
resistor was replaced with another only a few ohms different but it may be
the culprit. Hopefully that and not PCB damage - WTF Epox had to put the t/h
capacitors on the same line as the lugs for the cpu clip I don't know, hence
I "tried" pushing the clip off to the side with a flat blade screwdriver :-o
BTW, last night I had the mobo set-up with just (Cyrix) cpu, DIMM and AGP
card and a different PSU - AGP card's fan worked and the cpu warmed-up, so
there is power on the mobo elsewhere.

Keith

 

[JT]

Thanks JT, yep we're thinking along the same lines now - the one damaged
resistor was replaced with another only a few ohms different but it may be
the culprit. Hopefully that and not PCB damage - WTF Epox had to put the t/h
capacitors on the same line as the lugs for the cpu clip I don't know, hence
I "tried" pushing the clip off to the side with a flat blade screwdriver :-o
BTW, last night I had the mobo set-up with just (Cyrix) cpu, DIMM and AGP
card and a different PSU - AGP card's fan worked and the cpu warmed-up, so
there is power on the mobo elsewhere.

Keith

A few ohms in the 12v line to the fans would be major difference. The
little fuse/resistor is normally 1ohm or less. 12v line, 300ma per fan.
Only want a very small voltage drop. Other resistors in that area are also
somewhat critical. Some of them are terminating resistors and need to be
very close to the original value. A few ohms might different might not
work. If you put in a resistor with different value, that could very well
be a problem.

JT