This damage was caused by me mentioning to a friend
"I need to take the
motherboard out and drill a hole in the case for the I2C DIN socket..."
He took a B&D drill, loaded a 10mm bit and drilled the case. With the
motherboard still installed.
"Oh, I thought you'd already removed the motherboard...?"
ARGH! That's not pleasant...
I asume the next workpiece that drill was used on was your (ex?-) friend ;-)
No. But I did hurl a series of rather colourful adjectives at him...
Is that _all_ you hurled at him? I would have thought a medium-sized
mains transformer would be a suitable missile here :-). Even more so if
it has exposed connections and is plugged in at the time...
Is this the clipped-together membrane keyboard
that Acorn used at one
point?
I think so. It has the feel of a mid-90s PC keyboard...
Connection is via two plastic ribbon cables with black (carbon?) tracks
and contact pads.
Soudns like the Acorn membrane one. I may be confusing it with something
else (I've had hundreds of keybaords o nthe bench over the yers...) but
there's one where there's a plastic key greap with little plastic hooks
that fit through slots in the metal bakcing plate. You can carefully
free each hook with a small screwdriver (start in one corner) and lift
the metal plate off.
If o, I thin it comes apart from the bottom
(unclip the metal
backing plate, then take off the memberane layers). The LEds have their
leadouts bent over the keyboard moulding and come into contact with pads
on one of the membrane sheets.
I assume it can be reassembled without damage?
Yes. It just all clips back together again if it's the one I am thinking
of. Of course you have to be careful not to break the plastic hooks, but
breaking one or two won't make too much difference
Most membrane keyboards I've looked at can be disassembled, but are
either difficult or impossible to reassemble.
Many are heat-staked, which makes life difficult. I've never managed to
reassemble an LK201, for example. The IBM Type M can be done (yes, that's
a membrane keybaord), but you have to drill out the old stake posts on
the plastic chassis, tap them, and fit machine screws with nuts on the
underside. It's only worth doing because it's a Type M.
On the other hand, the membrane keyboard in the Tandy CoCo 2 and 3 is
assembled with lots of small self-tapping screws. It comes apart and
goines back together with few problems. And I've eseen severa; cheap
PC-clone keybaords where the membrane layers are held together by the
case (these keyboards have many screws on the bottom), again, you can
take them apart and put them together again (but it's questionable if
it's worth it :-)).
It's worth making sure it;s not contact
trouble between the LED and the
seeht before you replace them.
That's a good point... I might attack the LEDs with some contact cleaner
first, then.
Take the keyboard apart, clean the membeane pads and the LED leads with a
Q-tip and propan-2-ol. For obvisou reasons don't try to solder to the
membrane sheet...
And surely you know how to test LEDs... (analogue ohmmeter, some DMM
diode test ranges, battery and resistor, etc)
Indeed.
Using Mk.1 Eyeball, they're 0.1in pitch. A KK would probably
Watch out.. As you must know by now, there are 2.5mm pitch and 0.1" pitch
connecotrs, and it matters on something with 9 or 10 pins...
One of the many alternative uses for a roll of 'rainbow' IDC cable :)
I often use an offcut of stripboard or a DIL socket/IC for this....
Pass on
that one. What are your thoughts on the full-size DIN connector?
The connector isn;t too bad, athough I wish the isulator round the pins
was made of a plastic with a higher melting point. Often at least one pin
moves out of the right position when you solder them.
Ugh, too right on that point. I usually buy a socket and a plug, mate
the two connectors, put the whole thing in the Panavise then use a set
of 'helping hands' to hold the wires while I solder them. A little
over-the-top, but it keeps the pins nicely in line.
Sure. I do much the same thing (although I probably have a suitable
socket in the junk box, remember that a 6 pi nsocket will take a 5 pin
'B' plug, and an 8 pin circular socket will take 3, 5A and 7 pin plugs too.
I have a small metalwork vice on my electronics bench for criming IDC
sockets, holdign things when soldering, etc. I've never needed the
helping hands, I cna normally hold the cable by hand when soldering to a
DIN plug. Even if I do end up with burnt fingers...
Indeed... There are some phono plubs with a
sliding sleeve on the
outside so that the ground makes first, but they are not common...
I was wondering if anyone had done that...
I can't rememebr where I saw them, but it was one of the well-known
connector manufacturers who made them.
Nice idea, but expensive and I'll bet prone to
failure (springs don't
last forever).
Sure... But if the slding sleeve foe fail, the thing still works as a
normal phono plug, so you are no worse off.
Probably rather pointless too -- most of the time, phono plugs go in
when the stereo is set up, and are left until a house-move or whatever.
You don't live in my workshop... ;-0
-tony