I have a Dell Dimension 2300. P4 2.0 with 512 megs of ram.
I'll check on the bias. As far as the fan, would that be a Radio shack
item, or is there a place on line that sells fans?
The current one says DATECH 0925-12HBTA-2
DC 12v 0.70A DC Brushless Fan I don't know what any of that
means of course.....
If the spec is accurate, 0.70A is a very high current for a
rear exhaust fan, without question is it never using near
that much.
I've pulled a similar one out of a Dimension 2400, relubed
it with very thick oil and it worked fine afterwards... but
it might've used a different motherboard (this was an Intel
845 chipset w/integrated video & DDR memory, I don't
remember all the board in Dells, only the major details till
they get older and break down).
The 0925 generally means 92mm wide by 25mm thick, and it is
what is commonly used on the rear exhaust inside their green
plastic duct/shorkel/whatever that extends down over the CPU
'sink.
In the system I pulled that fan out of, it was running
pretty slow (RPM), what range is yours running in (high and
low if different as suggested by your description)?
What temp is the CPU under full load (Like running Prime95's
Torture Test, large in-place FFTs setting for 30 minutes)?
Under that load for 30 minutes, is the fan still surging or
contast high speed?
The issue would be determining what is necessary to keep the
CPU cool enough AND reduce surging if the motherboard is
going to perpetually do that. You might first check on a
bios update, apply it.
The issue might be that if the fan chosen is too low
(Initial) RPM, the CPU more quickly goes past it's threshold
temp which the control circuit senses and kicks up the RPM a
notch. This means choosing a higher speed (spec'd) fan
could actually result in quieter operation, except if you
often run anything at nearer full load and it would've
passed that threshold temp either way.
Thus it would be useful to find out if there is a bios
update (or bios settings change) plus relube the fan before
making further determination through full load testing of
what the resultant fan RPM is and the temp... THEN choosing
a suitable fan based on that data.
Does your fan use a 4 pin connector on the motherboard or
only 3 pin, and IF 4 pin, does it have all 4 wires going to
the fan or only 3? This is an important consideration as if
it only has 3 wires, or only 3 pin socket for connection, it
won't be using the Intel PWM control feature now present on
many boards. That feature can be a problem in itself, cause
surging like you describe but it can as easily happen
without it too... anyway, if it's using that 4th wire for
control then any 3 pin fan without it may work but not surge
simply due to lacking the feature suggort that is causing
it.
Generally speaking, the closest match to what you have that
I would pick would be a Panaflo FBA09A12M speed if the fan
did use the 4th wire for control, Panaflo FBA09A12H if it
didn't, or Panaflo FBA09A12L speed if you wanted to avoid
the connector altogether and connect to a non-controlled fan
header or use an adapter to connect it to a power supply
lead.
You'll also have to determine if the board bios allows
disabling the RPM sensor shutdown for the fan if system
shuts off without RPM signal... at least if you choose a fan
without RPM signal feature.
I figured that some of you gurus may know a place on line that sells this
stuff.
Everybody and their brother sells fans, but figuring out why
the original is surging is the first step... because after
relubing it, for the purposes of assessing system state it
should then be running ok without surge, or if it still
surges it's expected the problem will remain with a
different fan.
One place that sells a couple of the panaflos at low cost is
http://www.svcompucycle.com/standardfans92.html
but pay attention to the connector type so you get one
that's compatible (else you'll have to swap connectors,
solder old to new, or another improvisation to get it to
work).
