21 Jan
2008
21 Jan
'08
5:32 a.m.
The spacebar died on the last working 83-key XT keyboard I had (I have
three, and ALL have non-functioning spacebars), so I decided to finally
choose one to take apart and try to clean with compressed air, etc. All
of the keys came off okay; I put the plastic parts *only* in the
dishwasher (mild soap, warm water, nothing harsh) and cleaned the rest
by hand by shooting compressed air into every buckling spring hole. But
when it came time to put the spacebar back on, I noticed that both ends
of the spacebar have two little "hooks" that are supposed to hook onto
two little prongs of metal underneath the top of the assembly. These
provide necessary support, as the spacebar will bend if pressed at the
edges instead of going straight down. Only problem is, I can't seem to
get these re-hooked!
The only way I can see getting the spacebar back on, barring some trick
I don't know about, is to take the metal back off the assembly and try
to re-hook it from underneath. But I'm terrified that, if I try to take
the back off, 83 buckling spring assemblies are going to fly every which
way from the unit and I'll be left with a worthless hunk of junk. It
also doesn't look like it was meant to be taken off anyway, as one of
the metal tabs on mine seems intentionally bend downward to prevent this.
For those who need pictures, I've taken some snapshots of the problem
and put them here:
ftp://ftp.oldskool.org/pub/misc/keyb/
Any advice is appreciated -- either that, or a source for more 83-key XT
keyboards...
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
21 Jan
21 Jan
8:17 a.m.
On Sun, 2008-01-20 at 23:32 -0600, Jim Leonard wrote:
when it came time to put the spacebar back on, I
noticed that both ends
of the spacebar have two little "hooks" that are supposed to hook onto
two little prongs of metal underneath the top of the assembly. These
provide necessary support, as the spacebar will bend if pressed at the
edges instead of going straight down. Only problem is, I can't seem to
get these re-hooked!
What I do is hold the space bar with the top facing me, get the hooks
hooked under the metal "anti-roll bar" (sorry about the car reference
Jay, but that's what it is!) and then rock the space bar backwards until
the square plunger clicks into place.
YMMV.
Gordon
6:17 p.m.
Gordon JC Pearce wrote:
On Sun, 2008-01-20 at 23:32 -0600, Jim Leonard wrote:
Are you thinking of a Model M keyboard? They have a different spacebar
support mechanism than the 83-key XT keyboard I'm trying to repair.
If you aren't, then could you take a look at the pictures at
ftp://ftp.oldskool.org/pub/misc/keyb/ and see if yours looks like mine?
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
when it came time to put the spacebar back on, I
noticed that both ends
of the spacebar have two little "hooks" that are supposed to hook onto
two little prongs of metal underneath the top of the assembly. These
provide necessary support, as the spacebar will bend if pressed at the
edges instead of going straight down. Only problem is, I can't seem to
get these re-hooked!
What I do is hold the space bar with the top facing me, get the hooks
hooked under the metal "anti-roll bar" (sorry about the car reference
Jay, but that's what it is!) and then rock the space bar backwards until
the square plunger clicks into place. 
11:22 p.m.
The spacebar died on the last working 83-key XT keyboard I had (I have
three, and ALL have non-functioning spacebars), so I decided to finally
choose one to take apart and try to clean with compressed air, etc. All
of the keys came off okay; I put the plastic parts *only* in the
dishwasher (mild soap, warm water, nothing harsh) and cleaned the rest
by hand by shooting compressed air into every buckling spring hole. But
when it came time to put the spacebar back on, I noticed that both ends
of the spacebar have two little "hooks" that are supposed to hook onto
two little prongs of metal underneath the top of the assembly. These
provide necessary support, as the spacebar will bend if pressed at the
edges instead of going straight down. Only problem is, I can't seem to
get these re-hooked!
I don;'t want to worry you, but IIRC, all the keycaps were available as
FRUs from IBM _apart fro mthe space bar_. It was not regarded as
practical to remove and replace that. It is a fiddle.
The only way I can see getting the spacebar back on, barring some trick
I don't know about, is to take the metal back off the assembly and try
to re-hook it from underneath. But I'm terrified that, if I try to take
the back off, 83 buckling spring assemblies are going to fly every which
way from the unit and I'll be left with a worthless hunk of junk. It
also doesn't look like it was meant to be taken off anyway, as one of
the metal tabs on mine seems intentionally bend downward to prevent this.
The only way I've found to reassmble them is to take the whole thing
apart. it gives you a chance to properly clean it anyway.
1) Remove outer casing and keyboard cable.
2) Remove all keycaps apart from the spacebar (if it's still in place)
3) You mention a bent-over tap. This is, IIRC, on top of the keyboard,
and it's prrety clear it's been bent after assembly. Bend it back to
clear the slott in the other part of the kayboard.
4) Slide the bottom section relative to the top to free it. With the
keyboard upside-dwon, lift off the lower part complete with the PCB.
5) Remove all 83 spring/flap units. They're all identical AFAIk
6) Remove the space bar if it's still in place
7) If you want to, you can remove the PCB by undoing the earthing screw,
then sliding it to free the keyhole slots from the studs on the base
plate. There's a thin plastic insulator under the PCB, don't lose it!
8) OK, now time to putit back togther. Fit the PCB to the base and screw
down the earthing screw. Put the space bar back on and hook the wire
linkage the prevents it from tipping in place. Then pull the space bar up
as far as you can without disconnecting this linkage.
9) Fit the flaps, taking care to ket the space bar one correctly
positioned. Fit the base/PCB and slide it over to lock it. Don't bend the
tab yet. Prese the space bar down so it clicks in place, and check it
clicks and returns properly. If not, you need to take the baseplate off
again and have another go.
10 Fit the other keycaps, getting the springs located properly. Again
check eack one clicks and returns if not, Pull that keycap and try again.
11) Fit the cable and plug it into a PCB. Try the keyboard. If it doesn't
work, you might have to go through the whole process again, but most of
the time they do work
12) Bend over the locking tap, refit the case.
-tony
8:01 p.m.
On Monday 21 January 2008 23:22:00 Tony Duell wrote:
If that's refering to those infernal Haynes manuals, I think we're better
off without them....
-tony
12) Bend over the locking tap, refit the case.
It's not the same without the Terry Davey cutaway drawings and "Refitting is
the reverse of removal" ;-)
23 Jan
23 Jan
4:43 a.m.
First of all, a giant thank-you to Tony for getting it all right (from
memory, no less). Unfortunately, I still need advice:
Tony Duell wrote:
9) Fit the flaps, taking care to ket the space bar one
correctly
positioned. Fit the base/PCB and slide it over to lock it. Don't bend the
tab yet. Prese the space bar down so it clicks in place, and check it
clicks and returns properly. If not, you need to take the baseplate off
again and have another go.
While this fixed the spacebar, it has rendered other keys unusable. I
have taken it completely apart and reassembled it three times now and no
matter what I do, the return key is dodgy (doesn't always register, or
registers twice) and the numeric "-" is dead. I have looked at the
surfaces, both on the board and the buckling spring assemblies, and
everything looks clean -- I can't see why I'm getting screwball key
behavior on a few keys. I've completely rearranged the buckling spring
assemblies (they are identical) so I'm not sure what else I can do...
any advice?
On a side note, how does this mechanism work? I understand how the
buckling spring mechanism works, but it looks like a piece of plastic is
hitting two metal pads -- since plastic doesn't conduct electricity, how
is this working at all?
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
6:27 a.m.
[...] it looks like a piece of plastic is hitting two
metal pads --
since plastic doesn't conduct electricity, how is this working at
all?
Some plastics do conduct, at least enough to be useful. (A plastic not
designed to be conductive generally won't be, but that doesn't mean
anything about plastics designed for conductivity.)
/~\ The ASCII der Mouse
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1:26 p.m.
From: mouse at rodents.montreal.qc.ca
Hi
It could be capacitive. Plastic could be used in such a case
and wouldn't need to conduct.
Dwight
_________________________________________________________________
Connect and share in new ways with Windows Live.
http://www.windowslive.com/share.html?ocid=TXT_TAGHM_Wave2_sharelife_012008
[...] it looks like a piece of plastic is hitting
two metal pads --
since plastic doesn't conduct electricity, how is this working at
all?
Some plastics do conduct, at least enough to be useful. (A plastic not
designed to be conductive generally won't be, but that doesn't mean
anything about plastics designed for conductivity.)
24 Jan
24 Jan
12:33 a.m.
First of all, a giant thank-you to Tony for getting it all right (from
memory, no less). Unfortunately, I still need advice:
Tony Duell wrote:
If you get the right 'feel' and normal keyclick, then you've got it
together properly. If a key feels odd, make sure you've got the spring
correctly postioned in the keycap's stem.
Odd keys not working doesn't sound like an electronic fault (it's a
matrix of sensors, after all). So if the flaps are OK, the problem could
be :
Defective keycap (spring not located properly, can't locate properly)
Problems with the keyboard frame (flaps not moving freely)
PSB trouble?
9) Fit the flaps, taking care to ket the space
bar one correctly
positioned. Fit the base/PCB and slide it over to lock it. Don't bend the
tab yet. Prese the space bar down so it clicks in place, and check it
clicks and returns properly. If not, you need to take the baseplate off
again and have another go.
While this fixed the spacebar, it has rendered other keys unusable. I
have taken it completely apart and reassembled it three times now and no
matter what I do, the return key is dodgy (doesn't always register, or
registers twice) and the numeric "-" is dead. I have looked at the On a side note, how does this mechanism work? I
understand how the
buckling spring mechanism works, but it looks like a piece of plastic is
hitting two metal pads -- since plastic doesn't conduct electricity, how
is this working at all?
Sinve the flaps come down onto soldermasked areas of the PCB anyway, it
pretty much can't be conductive. I've always assumed it's a capacitive
sensor. When the flap comes doewn it increases the capacitance between
PCB pads, this is detected by that IBM sense amplifier chip (the square
metal thing)
-tony
5:24 a.m.
Tony Duell wrote:
Defective keycap (spring not located properly,
can't locate properly)
Problems with the keyboard frame (flaps not moving freely)
Definitely not a mechanical problem.
PSB trouble?
I guess :-( I took one of the buckling spring mechanisms and "manually"
struck keys with it, and also ran it lightly across the board. Most of
the keys worked except the ones I am having trouble with.
I guess I'm at the end of the line then?
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
7:45 p.m.
I guess :-( I took one of the buckling spring
mechanisms and "manually"
struck keys with it, and also ran it lightly across the board. Most of
the keys worked except the ones I am having trouble with.
Have you removed the PCB from the baseplate to look for possible damage
to the PSB or to the mylar insulator under it?. Is it possible there are
broken traces on the PCB?
Unfortunately, the scheamtic in the IBM Techref doesn''t include a
diagram of the key matrix. Which means it's not possible to see if the
keys you ar ehaving trouble with are in the same row or column (is it
just 2 keys?)
-tony
9:27 p.m.
Tony Duell wrote:
I have not removed it yet, although with broken keys I guess there's no
reason to hold back now. So I'll take the PCB off of the baseplate and
have a look.
I guess :-( I
took one of the buckling spring mechanisms and "manually"
struck keys with it, and also ran it lightly across the board. Most of
the keys worked except the ones I am having trouble with.
Have you removed the PCB from the baseplate to look for possible damage
to the PSB or to the mylar insulator under it?. Is it possible there are
broken traces on the PCB? Unfortunately, the scheamtic in the IBM Techref
doesn''t include a
diagram of the key matrix. Which means it's not possible to see if the
keys you ar ehaving trouble with are in the same row or column (is it
just 2 keys?)
Most of the keys having trouble were on the same horizontal line except
the enter key, but those may have been somewhat mechanical because
repeated use got them 90% functional. I'll try to visually inspect the
back of the PCB tonight, and put it together one last time. If nothing
is obviously wrong and it still fails, I will throw it in the spare
parts bin (and then tentatively start working on the other broken XT
keyboard).
Even if I find a trace issue, my skill with a soldering iron is worse
than that of a moose wearing boxing gloves, so I might ask my brother to
come over and help with the soldering (I was always the software guy,
and he was always the hardware guy :-)
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
26 Jan
26 Jan
9:25 a.m.
Tony Duell wrote:
I don't own a multimeter (don't kill me!) so I couldn't "officially"
check for broken traces. But I did separate it from the backing plate
and it looked simply perfect, like it wasn't more than a day old; if
there was a broken trace, it eluded me.
I've given up and relegated it to the spare parts bin with a note that
ENTER and KEYPAD MINUS don't work. I was manually bridging pads on the
board and those two keys were the only ones that didn't produce any
signal at all. I can only conclude that I must have banged it or
something taking it apart.
However, there is a silver lining: I used the experience of
disassembling and reassembling it a bazillion times to correctly repair
the spacebar on my OTHER XT keyboard, so I am back in business. So
again, thank you very much for the guidance!
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
I guess :-( I
took one of the buckling spring mechanisms and "manually"
struck keys with it, and also ran it lightly across the board. Most of
the keys worked except the ones I am having trouble with.
Have you removed the PCB from the baseplate to look for possible damage
to the PSB or to the mylar insulator under it?. Is it possible there are
broken traces on the PCB?
6181
days inactive
6186
days old
14 comments
6 participants
participants (6)
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ard＠p850ug1.demon.co.uk -
dkelvey＠hotmail.com -
gordonjcp＠gjcp.net -
gpearce＠curiousgroup.co.uk -
mouse＠Rodents.Montreal.QC.CA -
trixter＠oldskool.org