[rescue] Replacing CPU cooler fan on ultra 1

Mike Nicewonger twmaster at twmaster.com
Fri Jul 15 18:15:56 CDT 2005

On Jul 15, 2005, at 7:05 PM, Curtis H. Wilbar Jr. wrote:

> On Fri, 2005-07-15 at 06:52, Jonathan Groll wrote:
>> Hi there,
>> Can anyone tell me what the trick is to replacing the cpu cooler fan 
>> on
>> an Ultra1? There seem to be no instructions for doing so in the ultra 
>> 1
>> service manual that I have, is it perhaps in another manual?
>> There are five screws holding down the plastic plate that holds down 
>> the
>> fan. Four of these screws, directly surrounding the fan can be removed
>> from above. The fifth screw, on the far side of the plastic plate 
>> seems
>> to be inserted from UNDERNEATH  the motherboard. Also, underneath the
>> plastic plate appears to be a layer of a yellow foam or it could be
>> double-sided tape that may also be sticking this plastic plate to the
>> heatsink fins. Must the entire motherboard be removed and this double
>> sided tape as well just to replace the cooler fan?

Every Ultra 1 I ever saw with a fan on the CPU had the 'fifth' screw. 
What I've done is replace the fan with a similar sized one off of a 
PeeCee heatsink of some sort. Just remove the 4 screws then remove the 
fan. Then just slide the replacement into place and leave the 5th screw 
where it is. I just rebuilt the fan setup on 4 U's I will be putting 
into production as replacements for the older 4M gear I am pulling out 
of service.

> I've done this... (used an SS2 case cooling fan (larger and more
> durable... should outlast the U1 itself :-) ))....

Bigger fans are always a good choice if you can make them fit.

> I don't recall having to remove the motherboard... I remember removing
> screws and lifting the plastic and fan out... when it went back in
> I left the plastic out... as the screws were not long enough for the
> new thicker fan and the plastic.... and I didn't have any longer
> screws.....

> the plastic is just a shield to keep you from potentially damaging
> the heatsinks on the cache? chips when inside the unit....

That plastic cover channels air toward the heatsinks on the cache 
control chips. I'd find a way to keep it. Those cache chips get very 
warm. I had an UltraSparc 1, 200 MHz CPU module fail intermittently due 
to a cache module heatsink coming un-bonded from the chip.

>> The board is the version with the 3 SBus connectors and the CPU in
>> question identifies itself as an UltraSPARC 143MHz. The machine works
>> and turns on fine, but the non-working CPU fan gets quite hot.

You have a first generation Ultra 1 there. Not an 'E' model. Don't run 
it without the fan you'll cook the CPU.

> the one I did was in a U170E... but I doubt it is any different in
> that one...
> maybe someone else here knows your 5th screw mystery... my U1 is
> buried so I can't pull it out to look at it.
Mike N

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