Fan cooling options on the 3B1 (was Re: Boot problems on 3B1)

[Lenny Tropiano]

In article <228 at tarkus.UUCP> jcs at tarkus.UUCP (John C. Sucilla) writes:
|>In article <5649 at ihlpf.ATT.COM> gmark at ihlpf.ATT.COM (Stewart) writes:
|>>In article <227 at tarkus.UUCP>, jcs at tarkus.UUCP (John C. Sucilla) writes:
|>>> (another good reason to install a 110V. constant speed fan).
|>>
|>>I apologize for bringing this back to the net, but I've lost the
|>>old postings regarding fan mods.  I stuck with the DC fan, based
|>>upon the db listings on the packages.  An AC fan is noisier, right?
|>
|>Nah.
|>

Well, the 120VAC fan (at least the Radio Shack incantation of it) is noticibly
noisier than 12VDC fan that is supplied with the UNIX PC (even when that's
running at high speed).  It's not *unreasonable* by all means, in fact I've
learned to live with it for quite some time now (in my bedroom) :-).

|>>What is the reason to use the AC fan?  Operation in spite of
|>>power supply failures?
|>
|>Thats a good reason.  Another good reason is that the 12v fan is
|>junk.  Mine failed after 3 months and it seems a lot of others
|>have had them fail sometime in the first year.  
|>

Yes, agreed on this one.  The 12VDC fans that are in the UNIX PC's are
not worth too much (about $4.00 from a discount shop, $12.95 at Radio
Shack prices, $100 at AT&T's prices)... I've gone through all different
phases with fans.  I've tried almost every combination, and the best
so far is the current one.  1-120VAC fan running on the right side.

I've tried the Radio Shack 12VDC fan on the right (with and without
bypassing the thermal thinga-magig on the power supply).  While this
worked *ok*, I was still worried about the 12VDC fan's reliability.  

I've tried two 12VDC fans, this worked (or seemed to work) well.  This
pulled much too much dust through my machine, and probably pulled needed
air away from the right side.  (Like a few of you out in net-land suspected,
this wasn't as good of an idea as I first suspected).

Another problem I noticed with the Radio Shack version of the 12VDC fan is
that it only pulled 27CFM (cubic-feet-per-minute), and I think the AT&T
version pulled 31CFM.

The best configuration so far is the 120VAC fan.  It's easy to hook up,
looks reliable, and pulls about 34CFM.  

Installation instructions: 

Shut the machine down (of course), and remove the keyboard.  
Flip the entire machine from the front backwards, so that the metal 
bottom is facing you (the part with the serial #). Open the machine 
(the easy way)... remove the 6 screws that connect the monitor top 
to the bottom plastic base (Note: This is not the normal way to 
open the machine if you need motherboard access, this will only give you 
access to the floppy, power supply, and the fan)  Four screws are 
located on the left and right sides of the monitor facing out 
at you.  Then the two others are near the internal EIA port and the 
power connect in recessed holes on the bottom. After the screws are removed, 
flip the machine back in the normal upright position.  Carefully pull the top 
off by holding the monitor, pulling up and towards you.  There are two plastic 
tabs in the front that you need to be careful not to break off.  You might
hear a *snap* noise, this is nothing to be alarmed about, it is just the
tabs being unfastened.  Once you have the top off, you can tilt the monitor
on the side.

Remove the old fan by the red-connector between the fan and the P/S.  Slide
the old fan out of the slot (save for temporary replacement use).
Use electrical tape to cover the old connector to prevent anything shorting
against the 12 volt supply. (*ouch*)  Place the 120VAC fan in the hole
where you removed the old fan.  Connect both wires directly to the AC
input (where those blue and brown wires are).  Solder them in place, polarity
not making any difference here [Thanks Gil, :-)]  Boot the diagnostic
floppy while the machine is open to make sure the fan spins when the power
is turned on.  Another caution is to make sure nothing rubs against the
new fan (ie. the black power cable to the hard drive). 

If everything checks out (the fan is blowing in the correct direction),
put the monitor top back on and tighten all the screws.

(*Note:         This does void your AT&T warranty and service, so do beware*)
(*Double-Note:  I don't take and responsibility in this venture or any other
		hardware tinkering I might suggest*)

Good luck with all this...

-Lenny
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