AC Cooling Fans

[Norman Yarvin]

In article <201 at bongo.UUCP> julian at bongo.UUCP (julian macassey) writes:

>    In response to the continued discussion on cooling the 3b1, here are my 
>AC fan installation notes.

Here are a couple of remarks on them.

>        You  will need a  three inch  axial fan  (115V) [..]

The place for the fan is actually a bit larger than 3 in.; the existing fan
is 3 1/8 in., and you can fit in a 3 1/4 in. fan.  The existing fan is 1 1/4
in. deep, and it has a grate attached to it with double-sided foam tape
which extends it to 1 1/2 in.  You can fit in a 1 5/8 inch fan at most.

>                        __________________________
>                        |+----------------------+|\
>                        ||@@@@@@@@@@@@@@@@@@@@@@|| \_
>                        ||@@@@@@@@@@@@@@@@@@@@@@||   |
>                        ||@@@@@@@@@@@@@@@@@@@@@@|| A |
>                        ||@@@@@@@@@@@@@@@@@@@@@@||   |
>                        ||@@@@@@@@@@@@@@@@@@@@@@||  _|
>                        ||@@@@@@@@@@@@@@@@@@@@@@|| /
>                    +---||@@@@@@@@@@@@@@@@@@@@@@||/---------+
>                   / == +----+--------------+----+ ==A===  /|
>                  / =======  |      A       | /  =======  / |
>                 /____A______|______________|/___________/B |
>                 |###########|_____________________A_____| /
>                / #C                                #C  / /
>               /___________________B___________________//
>               |______________________________________|/
>
>A is Monitor cover. B is base cover, leave on for fan replacement.
>
>8) Grab the phillips, and use it to remove the 2 vertical screws in the
>   back  of  the  monitor  case.  They  are normally  hidden  by  the 
>   peripheral plugs.

Note that these are the screws which connect A to B, not any screws that go
into the actual box that contains the monitor.

>10) Carefully lift the monitor up and towards the front of the machine - you
>    may need to use the larger flat-blade screwdriver to pop the front part
>    the case (next to the floppy drive) off. Be careful here.
>11) Set the monitor on its side.  You may need to cut a cable tie to get
>    sufficient slack.

The whole top of the box (parts A and B together, normally removed as a
unit) is designed to be lifted off the base of the machine and tilted
backwards: then it rests (without having to disconnect any wires) on its
back quite nicely.  The front part of the case (right in the middle)
contains a ratchet type mechanism for holding parts A and B together, which
is hard to release:

	BBBBBBBBBBB
		  B
		A B
	disk    AAB
		ABB
		A B
		AAAAAAAAAAAAAA

>14) Using needlenose pliers remove  the Power spade connectors  from 
>    the back of the IEC Power connector and switch assembly.      
>15) There should be at least a 4 ins pigtail of power lead on the fan. 
>    Strip at least 1/2 in from each wire.
>16) Each of the spade lugs  has a little hole in the  middle. Put a 
>    stripped wire through each hole and bend over.
>17) Push the connectors back on the spade lugs. This should leave no 
>    uninsulated wire protruding. Adjust if neccessary.

Yeeeagh! This is a neat idea, but the connection formed is less than
optimal, to put it in polite terms.  I would advocate either
	(1) doing this the way I did, by buying appropriate spade lugs, and
making the following device:

		(power jacks)
		|	|

	{	V	V		<--- PLUGS SOLDERED TO WIRES
  you	{	|\	|\
  make {	| \-------======== (fan)
  this  {	|	|
	{	|	|		<--- PLUGS SOLDERED TO WIRES

		V	V
		|	|
		|	|
		(wires that went
		to power jacks)

	---OR---

	(2) putting the wires in the holes as in the original article, then
soldering them in.  This is easier, and if the soldering is done without
leaving too much excess solder, it should still be possible to put the
original plugs back on.  In addition, this is an inherently permanent
modification of the machine.

>19) Seat the fan in the cavity  and  take care that the  Hard  Drive 
>    power  cables  are not obstructing  the  fan blades. Adjust  cable if 
>    needed. Spin blades by hand to be sure.

The existing fan will have a grill over it, attached by the aforementioned
double-sided tape.  If your new fan is small enough (mine wasn't), you can
unstick the grill from the stock fan and stick it on your fan.  Then you
don't have to worry about cables getting in the way.


For those who would attempt this without knowledge of how to solder:

#1:  Solder it anyway.  Buy a soldering iron from Ripoff Shack, and
experiment for a while.  Your connections should be good enough so that a
medium-light yank won't break them; if you can yank on it, you have a
connection, otherwise you don't have a connection.  Your connections should
not be large globs of solder, nor should they be incomplete. (the 3 second
guide to soldering)

#2:  Use method 1 from above.  That way, you won't have to screw around with
the soldering iron inside the machine, but can assemble the extra stuff
before starting, and spend enough time to get it right.  Those spade lugs
can be very hard to solder; again, it's better to do it outside the machine.

Good luck!  May you not need it!

P.S.:  I would like to attend the Unix PC BOF in Baltimore, but mail to
Lenny Tropiano bounced.  Do you have to attend the conference to get into
the BOF? (I won't be).  My Unix PC is available for any non-destructive type
(and even certain destructive types) of experimentation/testing.

					Norman Yarvin
		(seismo!umcp-cs | allegra!hopkins) !jhunix!ins_anmy
		or yarvin at cs.jhu.edu

  "Obviously crime pays, or there'd be no crime." -- G. Gordon Liddy