[vox-tech] Demo Machine: Stopped Rear Case Fan.

[vox-tech@lists.lugod.org]

On Sat, Jun 08, 2002 at 01:14:49AM -0700, Bill Broadley wrote:
> On Fri, Jun 07, 2002 at 05:50:33PM -0400, msimons@moria.simons-clan.com wrote:
> >   A while back I commented that the read case fan had failed.
> > One of the things I did yesterday was to swap the front and rear case
> > fans to see if the fan was operational or not.  It turns out that the
> > fan is 100% operational...
> 
> I assume the old front fan that is the new rear fan didn't spin up.

  Yes.

  Before swap: front fan spinning, rear fan stopped.
  Swap front fan with rear fan.
  After swap: front fan spinning, rear fan stopped.
  [Since this didn't fix anything I swapped fans back to their 
   original locations]

> >   I think the motherboard isn't suppling power to the back case fan
> 
> It's likely dead, abit bp6's are famous for this, no idea what
> kind of motherboard this is.

  Tyan Tiger 100.

> >   Another defect appears that the SMBus chips can not read the 
> > CPU1 Fan speed...
> 
> Is the cpu1 fan connector connected to a fan with 3 wires?  2 wire
> fans will spin but not show rpm.

  Yes, three wires.

> > - Someone with electrical skills want to test out the three pin 
> >   fan connector to figure out what is going wrong?
> 
> I'm betting on a short.

  Would this short release the magic smoke, or if the short is 
corrected would the thing be operational.  (I've not taken the
motherboard off the backplane to see if something is caught underneath,
this connector is extremely close to one of the motherboard mounting 
pins).

> > - Any suggestions on how to get the fan spinning? (1)
> 
> Get an adapter from the standard 4 pin power supply to whatever
> the fan takes.

  I took a different tact... I routed the CPU1 fan to the CPU2 
connector, then the case fan to the CPU1 connector.  Now all four
fans in the machine (power supply, two case, and one processor)
are all operational.
  I was going to connect case fan to CPU2 but would not reach.

  The interesting thing is the lm79's fan RPM information still
only reports one set of RPM information... now "fan3" is reporting
when "fan2" used to report.  I haven't figured out if the fan3 numbers
are for the front fan or not.

> > - Has anyone else seen motherboards fail to spin fans like this?
> 
> Common on abit's, most often when using a higher performance (more
> power hungry) fan, or when plugging/unplugging fans while
> the machine is on.

  These are large case fans (about 5 inches square).  I doubt that
anyone messed with the fans while the machine was operating since 
it was given to us... based on Henry's comment that the back case
fan has never functioned.

  I was thinking that this defect might have been why this machine
was donated... it would have failed a QA check and customer 
inspection would have most likely resulted in a return.

    TTFN,
      Mike