3b1 Disassembly, 2nd Attempt
Thad P Floryan
thad at cup.portal.com
Sun Jan 6 20:35:35 AEST 1991
michael at yonder.UUCP (Michael E. Haws) in <422 at yonder.UUCP> writes:
I posted this question a few weeks back but received no response.
Since it is possible that folks/machines were away for the holidays
I will try again.
Recently, within the last month, someone( probably one of the hardware
gurus) posted some instructions for repairing/replacing some internal
part of the 3b1. The instructions were very detailed and I would like
to have a copy but alas the article had expired on my machine. I was
not particularly interested in the part that had to be replaced, rather
the instructions for disassembling the 3b1.
Seems like maybe 3b1 Disassembly instructions might be a good thing to
go into the FAQ.
Yep, PORTAL was acting up during that period or I would have seen your original
post. Here goes ...
The following is extracted from a posting re: HD2 upgrade by:
jbm at uncle.uucp (John B. Milton) in <1990Nov23.040542.9357 at uncle.uucp>
posted on 23 Nov 90 04:05:42 GMT
-------------------- begin included material --------------------
Shopping list:
1. Small and medium phillips screw drivers.
2. Small flat blade screw driver, for serial cables.
3. Medium plyers or small adjustable wrench.
[...]
9. A grounded wrist strap. Use the right part so you don't get fried. There
is usually a 1M ohm resistor in series with these things to make sure only
high voltage static electricity is conducted from your body. If you like to
live dangerously, forget the strap.
10. An anti-static mat or a large piece of anti-static (pink) packing bubbles.
[...]
18. Cup or tray for screws. You may want to use a bunch of little ones.
[...]
Procedure:
1. Shut down UNIX.
2. Turn the power off.
3. Unplug the power cord at the machine.
4. Put on the wrist strap.
3. Unplug everything. This includes serial (you may need a small screw driver)
,
parallel, phone, keyboard (there is a little clip, like the phone lines).
4. If you have an expansion box, the long cable can not be disconnected at the
UNIXpc or the box, so the controller card in the UNIXpc must be removed.
There are two tiny phillips screws on the plate, next to the cable. Any
other expansion cards do not need to be removed.
5. Remove the two phillips screws on the back that fasten the plastic to the
metal frame. These are horizontal and go in from the back. There is a littl
e
tab right next to it. There are two others near-by that go up and are in
a circular recess. These should not be removed, they are two of six that
hold the top and bottom halves of the plastic together.
6. Remove the plastic caps on the two posts where the keyboard sits, and remov
e
the two screws. Ahhh, so that's why those are there!
7. Remove the top, plastic part of the case. This is easier said than done.
There are two or three rachet hooks in the plastic of the case at the very
front of the machine. These latch into the sheet metal base where you can't
see. It takes two hands to lift up on the case, and two hands to pry the tw
o
or three rachets ALL at the same time. If you get the rachets loose, don't
let the case fall back down or they will click back in. At this point the
back of the case will already be loose. No, you can't just lift the back up
far enough, there's wires still connected. Once the rachets are loose, lift
the platic case, monitor and all straight up about 4 inches. Be surprised a
t
how much that *#&@$ monitor weighs. Tilt the whole mess straight back so
that the monitor is laying on it's back, screen up. You will have to lay it
down quiet close to the back of the machine because there is a video cable
and three power wires still connected. Go ahead, scream and yell, that was
a
bitch to do.
8. Disconnect the video cable. There are two screws holding the video cable
down. One is up on a piece of sheet metal in the back left corner. The othe
r
one is down on the left side. Follow the cable and you will find them. To
disconnect the cable itself from the mother board, do not just pull, reach
in and grab the connector. You all do this with power cords, right?
9. Disconnect the brown and blue power wires from the socket/fuse assembly.
Sometimes these get chewed up in the fan, so check them for damage and tape
if necessary.
10. Disconnect the green plastic covered braided ground wire. Sometimes you
can get it off on the fuse assembly side, sometimes you need to remove the
screw on the power supply side. The top plastic with monitor attached is
now free. Let that snickering fool next to you pick it up and see how heavy
it really is and move it out of the way.
11. Remove the three screws that hold down the large, flat metal plate on top.
They are located at the very front of the plate. The floppy and hard drive
and the power supply are bolted to this plate, so they must all be
disconnected in order to get the plate off.
12. Disconnect the power supply. There is only one connector, a big heavy duty
ribbon cable which plugs directly onto the mother board. Lift up one end
and then the other until you wiggle it off. This will give you enough slack
to get the plate up and vertical, so you can get at the floppy and hard
drive cables. When this connector get dirty, it can cause all kinds of
weird system failures. Increasing the load on the power supply or bumping
the machine can cause panics. To clean this connector, just pull it off and
put it back on a couple of times.
13. Disconnect the floppy power connector on the back of the floppy drive. This
is the small white plastic connector with four wires going to it.
14. Disconnect the hard drive power connector on the back of the drive, same as
the floppy power connector. If this power cable comes directly from the
power supply and not the mother board, then you have a 3b1 and can leave
it connected.
15. Slide the plate forward. Examine where the back of the metal plate hinges
into the bottom sheet metal. There are two pins in the plate that fit into
upside-down T slots in the base, one on each side. The pin is sitting in a
groove in the back of the T. The idea is to lift the plate a little, then
slide it all the way past the middle, to the front of the T. Note that this
part of the base is frequently bent, and may need to be bent back into
shape before the plate can be moved around.
17. Tilt the plate up. Once the plate is all the way forward, it can be tilted
up vertical. You will not be able to get the plate all the way up if you
have a full height hard drive. If you have a half height hard drive and
you get the plate up, it may FEEL secure when it's vertical, but it is
VERY close to balancing, so get someone to HOLD IT vertical or tie it.
16. Disconnect the floppy ribbon cable (the wide, flat one) at the mother board
.
Remove it the same way as the power connector.
17. Disconnect the two hard drive ribbon cables at the mother board. You should
not have to unbolt anything on the plate. The ribbon cables should still be
connected to the drives.
18. Get the plate all the way off. Untie the plate and swing it carefully back
down flat. Lift the plate up and get it out of the front groove, then slide
it back into the middle groove. Once there, slide it up and out of the T.
Once again, it likes to jam here, so you will need to lift both sides
evenly. You may need to bend the T part a little to get the plate to slide.
Set the plate aside carefully, your hard drive is on there!
19. Take a break, get a soda, oogle the mother board and ALL THOSE DUST BUNNIES
!
I can tell, you're picking dust bunnies already. Just get the big ones off
now, you can blow all the little stuff off OUTSIDE when the mother board is
out. Now for a quick tour of the mother board. (coordinates in parentheses)
The BIG chip in the middle is the 68010 (14E). The two wide chips together
in front of the 68010 are the boot ROMs (14C and 15C). The wide chip to the
right is the 6850 serial chip for the keyboard (13G). The purple chip with
two lids on the right side next to the power cable is the WE 882A switched
capacitor modem chip (2K). The rows of chips in the front right corner is
the main memory (2A to 10H). Now look on the left side. If there is a large
L shaped PC board ON TOP of the mother board, you have a VERY old machine.
This board contains all the discrete logic that's in the three custom chips
on the newer mother boards. If you have the L shaped board, then changing
the battery can be quite complicated. If you don't have it, the 3 wide, 40
pin chips with VLi on them are the custom chips. The one to the left of the
boot ROMs is the video chip (17C). The other two are the DMA dat and DMA
address chips (22E and 22H). I don't know which is which. In the back left,
the chip with WD1010 or WD2010 is the hard disk controller (21H). Straight
back from that is the 7201 serial chip, which provided two serial ports, on
e
for the serial connector on the back and one for the on-board modem (21M).
Immediately to the left of that is the WD2797 floppy disk controller (22M).
I am looking at a newer mother board which has a floppy controller made by
VLi (VL2797). In the far back left corner are three empty IC sites (25-27P)
.
The one all the way on the left is 27P, where the P5.1 socket will go. You
may have a small trimmer resistor on the right one (25P). Older boards don'
t
have this trimmer, newer ones have it at 22P. This trimmer is for an added
floppy adjustment (you need a scope and instructions to do the adjustment).
On left side in front (under the L shaped board if you have it) Is the
battery (~27E). Your battery may be a cylinder or flat shinny thing. There
have been several postings on how to change the battery. There is a
removable jumper right next to it, which can be disconnected to save the
battery when the machine is being stored. You'd do all this to disconnect
the battery, wouldn't you? You can see the four LEDs (four? see HwNote01)
right along the left edge, in front (~28B). In the back right corner, under
the tin, is all the yucky stuff for the phone: transformers, relays, caps,
fuses, optoisolators (1M to 12P and 13P to 21P). The video RAMs are the
four chips at 14A, 15A, 16A and 17A. The memory mapping RAM is the fours
chips at 19C, 20C, 21C and 22C. There are various numbers about the revisio
n
level of you mother board along the left edge in back and behind the speake
r
volume control along the right edge, in front. I think the most important
are the ones next to the volume control. The bar code is the official
tracking serial number of the board, and there is a REV x sticker here.
20. Remove the little plastic clip on the volume control, right side, in front.
This is done by getting it up and off the actual volume control and sliding
it all the way to the back, where it will come out of the metal base. The
clip and the post coming out of the volume control are wimpy plastic, so if
you break it, you will be stuck with the volume in one position!
21. Remove two phillps screws on the sides in back.
22. Remove two phillips screws on the bottom in back.
23. Remove 10 phillips screws around the edge of the mother board.
24. Remove 4 hexagon posts in the middle of the mother board. Do not confuse th
e
hex posts with the bunch of short posts on the left side. Some mother board
s
have short posts, some don't the short ones are SOLDERED on, and won't come
off. The short ones are there to hold the proto version of the custom chips
.
Newer mother boards won't have the short posts at all.
25. Remove the mother board. Grab ahold of the short metal plate in back and
pull straight back. Careful! You will be pulling the mother board out of th
e
edge connector at the front of the machine. You also have to get the back
metal plate loose. Sometimes this gets bent and jams. Break each side loose
without bending the plate, then wiggle the back of the mother board around
gently until you're sure the plate is loose. Pull straight back to get the
mother board out of the bus board edge connector. Lift the mother board out
of the base by the back plate and the power connector. Put it down on the
anti-static mat. Pick up the base and set it aside.
26. Remove the two hex bolts from the serial and parallel connectors. Use needl
e
nose plyers or a small adjustable wrench. The back plate will fall off with
the last one. Take it off and put the 4 hex bolts back into the serial and
parallel connectors so you don't loose them. Put the back plate with the
base.
-------------------- end included material --------------------
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