pschmidt@bbn.com (Peter H. Schmidt) (04/21/89)
In an attempt to repay some of my information debt to this newsgroup, I'm
posting a detailed description of how to fix the chirping of your 3B1's hard
disk. I'm indebted in this to the 10 or so people who responded to my
original posting. I combined what I thought was the best advice and tried it,
and it worked fine - my machine is now as quiet as my diskless sun at work.
Type "n" now to skip the details...
Discussion:
My original posting asked about an annoying chirp/squeal that my 3B1 had
started to make continuously. I was afraid it was a bearing going in the disk
drive, but it turned out to be (as many people reassured me) the anti-static
tab vibrating as it made contact with the disk drive spindle. This tab is a
piece of copper that is mounted on the disk controller and which reaches up to
touch a small carbon disk glued to the end of the disk spindle. (See Fig. 1)
Over time, the carbon abrades unevenly, and can cause resonant vibration of
the tab.
Fig. 1 Anti-Static Tab (side view)
------
| |
hard drive -------- spindle
| |
|_________ __________________
\________________|_______|______________/
C disk---> \#####/
-_--------\
\ <-- Cu tab
=========================================\==========================
/
controller board (chip side)
Three basic solutions were suggested to me: lubricating the tab, bending it
down so that it doesn't touch the spindle, or bending it up so that it
makes firmer contact and doesn't vibrate. All three had been successfully
applied by people who wrote to me. I decided to bend the tab up and
lubricate it; that way the tab would still do its job, and hopefully wouldn't
abrade the carbon again soon.
The phrase "No user-servicable parts inside" takes on a whole new meaning with
the 3B1. It is a pain to take apart. I find it useful to use the marker (see
bleow) to mark the small parts and their sources uniquely (taking my memory
out of the loop on these jobs works wonders).
You will be removing all of the plastic casing to do this job. It comes off
in two pieces: the monitor/hard disk cover (labelled with A's in Fig. 2), and
the "chin piece" around the motherboard (labelled with B's). The monitor
cable goes down through a hole in the center of the case, and it has very
little slack. I had to cut a cable tie to be able to lay the monitor and
cover next to the base.
Six long, vertical screws hold the monitor case on. There are two on each
side, and two in the back. Four screws hold the chin piece on: two in front
inside the little keyboard clips, and two (horizontal) in back. These screws
have washers.
Once the plastic pieces are off, the rest of the job consists of removing
the ground shield on the hard disk, flipping the hard disk over, unscrewing
its controller, cleaning and lubricating the anti-static tab, bending it
toward the disk slightly, and then putting everything back together.
Tools required:
o grounding bracelet
o phillips screwdriver (med. sized)
o 1 small flat-blade screwdriver
o 1 medium sized flat-blade screwdriver
o 1 "force-nut" (?) screwdriver - the kind with a tip shaped like an
asterisk (*)
o a pair of needlenose pliers
o a jack knife
o flashlight
o can of WD-40
o Q-tips
o indelible marker (optional)
Fig. 2 3B1 - Front View (keyboard and mouse omitted)
------
__________________________
|+----------------------+|\
||@@@@@@@@@@@@@@@@@@@@@@|| \_
||@@@@@@@@@@@@@@@@@@@@@@|| |
||@@@@@@@@@@@@@@@@@@@@@@|| A |
||@@@@@@@@@@@@@@@@@@@@@@|| |
||@@@@@@@@@@@@@@@@@@@@@@|| _|
||@@@@@@@@@@@@@@@@@@@@@@|| /
+---||@@@@@@@@@@@@@@@@@@@@@@||/---------+
/ == +----+--------------+----+ ==A=== /|
/ ======= | A | / ======= / |
/____A______|______________|/___________/B |
|###########|_____________________A_____| /
/ #C #C / /
/___________________B___________________//
|______________________________________|/
Procedure:
0) Do a full backup of your drive.
1) Make sure you have a cleared off table or desk with 4'x4' of space to put
the machine on.
2) Use /etc/shutdown to halt your machine.
3) Boot the diagnostic floppy, and park the hard disk's heads.
4) Turn the machine off, and unplug the keyboard and power cables.
5) Turn all your peripherals off, and disconnect them from the machine.
6) Place your 3B1 on the edge of your cleared-off table, with the rear of
the machine projecting over the edge.
7) Grab the phillips, and use it to remove the 2 vertical screws in the
back of the monitor case.
8) Remove the two horizontal screws that are just inside the right and
left edges of the back fan gratings.
9) Hang one side over the edge and remove the two vertical screws there;
repeat for the other side.
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.
11) Set the monitor on its side. You may need to cut a cable tie to get
sufficient slack.
12) Attach your grounding bracelet to the metal case.
13) Unscrew the clamp holding the monitor cable to the left rear corner of
the metal case.
14) Use the small flat-blade screwdriver to pop the little plastic covers out
of the keyboard tabs (labelled with C's in Fig. 2).
15) Remove the screws from the keyboard tabs.
16) Work the chin piece up, and then lean it up against the monitor (watch the
monitor cable). If it seems stuck, check the left rear corner for a
6 wire connector in the way. Unplug it with the needlenose if need be.
17) Unplug the monitor cable (on the left side) and the power-supply ribbon
cable (on the right).
18) Remove the three screws along the front edge of the machine.
19) Tilt the sheet metal plate holding the disks and power supply (henceforth
called the "upper plate") upwards, while sliding the metal bolts
in the back corners along their guides and into their notches.
20) Pull up gently on the metal ground cage around the hard drive - you may
need to use the small flat-blde screwdriver to push its tabs through
the slots in the upper plate. Remove it and set it aside.
21) Loosen (do not remove) the four screws holding the drive to the upper
plate.
22) Move the drive so that the screw heads can pass through the big end
of the keyhole slots they're in.
23) Carefully turn the drive over, exposing the chip side of the controller
card.
24) Use the force screwdriver (?) to remove the five screws holding the
controller board to the drive (1 in each corner,and 1 in the middle).
26) Carefully unplug the printed cable and two wire connector from the
side of the board.
27) Tilt the board, and observe the copper tab and carbon disk (upside
down from Fig. 1).
28) Leave the room (to minimize the effect of overspray) with a Q-tip and the
WD-40. Soak the Q-tip.
29) Rub the Q-tip over the end of the tab, and over the carbon disk. Use
more Q-tips to remove any grit collected around the disk.
30) Carefully bend the tab toward the disk with the small flat-blade
screwdriver. Don't push too far.
31) Reassemble machine. (Don't forget the keyboard.)
32) Put diagnostic floppy in and turn on the power. Listen to the lack of
squeal (hopefully...).
33) Run the system diagnostics, just to be safe.
34) Reattach peripherals, reboot UNIX.
No sweat!
--Peter
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Peter H. Schmidt | All sweeping generalizations are invalid.
BBN Advanced Computers Inc.| The one intolerable is intolerance.
10 Fawcett St. | Loving thy neighbor usually isn't worth the
Cambridge, MA 02238 | effort.
(617) 873-4311 | (I speak only for myself.)
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