FUNKYWARE.ORG - TT_KEYBD.TXT - 11.07.1997

NOTE: the following text explains how to fix a defect that
      plagues both MEGA-STE and TT keyboards alike, making
      the CONTROL key inoperative.

      Preventive maintenance on keyboards not yet affected
      should also be performed. This involves opening your
      keyboard as explained below and sticking a length of
      insulating tape over the sensitive areas, to protect
      the mylar from eventual damage.

      While every precaution has been made for accuracy of
      the information, neither Mario Becroft nor Funkyware
      offer any guarantee about the results.

                 ATTEMPT AT YOUR OWN RISKS !!!

***
Date: Fri, 27 Jun 1997 11:13:22 +0000
From: Mario Becroft  mb@tos.pl.net
To: q-funk@megacom.net
Subject: TT keyboard fix</B>


TT KEYBOARD REPAIR


DISCLAIMER

While I believe that the repair described in this document is
reliable when carried out correctly, and while I have made every
effort to ensure that this document is accurate, I can offer no
guarantee with regards to the repair, nor your workmanship in
completing the repair. I am confident that the repair will work,
if completed with reasonable care, but I cannot guarantee this.
CARRY OUT THIS REPAIR AT YOUR OWN RISK! If you do not think you
are able to complete the repair, I advise you NOT to attempt it.


THE REPAIR

A common problem with TT (and presumably M-STE) keyboards relates
to the control key. After a period of time, the control key will
cease to operate. This problem happens because an edge in the
internal keyboard casing rubs on the keyboard mylar and eventually
rubs through the track that connects to the control key. This
problem does not appear to affect any other keys.

If the problem has not yet occured, it may be advisable to take
preventive action. Although I have not tried this, I suspect that
by either putting a protective covering of some kind over the
track, or by carefully filing away slightly the plastic casing
in the affected area, the problem could be avoided.

If the problem has already occured, fixing the problem requires
rejoining the broken track. The method described below has been
used on a number of TT keyboards and, provided it is done with
care, seems to have a very good success rate. Every keyboard that
I have repaired in this way have worked flawlessly ever since.

You will probably be able to complete the repair in an hour or so.
Be sure to read the instructions completely before carrying them
out so that you are familiar with the repair. Take it slowly and
exercise care in completing the repair.

First, the keyboard must be disassembled. The removal of the three
screws that are present underneath the keyboard will allow the
outer casing to be removed. It is then necessary to disconnect an
earth wire by unscrewing the connector, and it would be advisable
to unplug the two ribbon cables joining the keyboard unit itself
to the PCB.

At this point you should have the black plastic keyboard case with
metal backing completely disconnected from the keyboard casing and
PCB. You can now proceed to removing the metal backing from the
keyboard. The backing is attached by a great number of clips, all
these clips must be carefully opened. An easy way of accomplishing
this is to work from one side to the other, until the backing is
disconnected from all the clips.

You should now observe the keyboard mylar, which can be removed
from the keyboard. The mylar is where the problem lies, so the
rest of the keyboard can be set aside while you work on the mylar.

Looking at the mylar from the top, you will observe a track at the
far upper left hand corner that connects to the control key. The
upper left hand corner portion of this track is where the problem
lies. The break may not be visible at first but, by careful
observation, a rough breakage in the track should become apparent.
Fixing the keyboard requires rejoining in the track at this point.

EXTREME CARE is required in carrying out the next steps,
particularly when punching the holes in the track. Read through
the steps carefully before you start so that you are familiar with
what you will be doing. Take it slowly and carefully, and the
operation will most likely be a success.

Examine the area around the breakage. You will be punching about
three holes in the track, evenly spaced approximately 5mm apart on
either side of the breakage. These holes need to be EXACTLY IN THE
CENTRE of the track and must be VERY SMALL. You will need a needle
with a fine point (such as a sewing needle) to make these holes.
A single strand from a multi- strand wire will be later threaded
through the holes, and the wire must fit firmly, not loosely in
the holes. Therefore the holes must be very small.

Working out from the breakage, and with the aid of the needle and
a magnifying glass, VERY CAREFULLY make three holes on either side
of the breakage, evenly spaced approximately 5mm apart. Ensure that
the holes are EXACTLY IN THE CENTRE of the track and VERY SMALL.
Make the holes one by one, and check that each hole is the right
size before you make the next hole. Check the size by attempting
to thread a single strand from a multistrand wire through the hole.
The strand should fit firmly in the hole. Remember, there is no
going back once you have made the holes, so ensure that you make
them very carefully and accurately.

Now that the holes are complete, it is time to thread a single
strand from a multistrand wire through all of the holes. Get a
piece of multistrand wire and extract from it a single strand,
long enough to cover the length of all of the holes you have made
in the mylar with substantial length to spare. Carefully thread
the wire through the holes one by one, pulling the wire tight
after each hole. Leave a short length (a few mm) protruding from
the first hole. The wire should fit firmly in the holes, and it
will require care to thread the wire through the holes because of
this firmness. The wire should be threaded alternately up and down
through the holes so that it joins the track where the breakage
is. When you have finished, cut off the ends of the wire so that
a few mm of wire is left protruding from the end holes. Pull these
ends tight and push them flat against the mylar.

The most difficult part of the repair is now complete. It is still
necessary, however, to finish the repair properly. If the wire you
have added makes electrical contact with the metal backing that
attaches to the keyboard, the the keyboard will not work. For this
reason, it is necessary to place insulating adhesive tape between
the wire and the metal keyboard backing. It is also important that
the wire does not touch and other tracks on the mylar, or obstruct
the passage of any keys.

Once you have ensured that everything is as it should be, it is
time to reassemble the keyboard and try it out. Reassembly is
generally simply the reverse of disassembly. Reattach the metal
backing (which is much easier than detaching it) then reconnect
the two ribbon cables and the earthing wire. Do not entirely
reassemble the keyboard, instead plug it in in its partially
assembled state and test it. Check that ALL the keys work. In
particular, check that the control key works. Check that random
characters are not sent when the control key is pressed. If all
is well, you can finish reassembly of the keyboard - you have
finished. Congratulations!

If there was a problem, then check, first of all, that the two
ribbon cables are correctly and fully in their sockets ensure
that the metal backing on the keyboard is fully attached, with
all of the clips attached correctly. If it still does not work,
determine the symptoms of the problem and refer to the following
list of possible problems:

* The control key still doesn't work, but everything else is fine.

   This means that the repair has had no effect. Remember that
   the wire must join the two sides of the break in the track.
   The holes should be on either side of the break, and the wire
   should join the break. Check that the wire fits firmly in the
   holes and that the holes are exactly in the centre of the
   track. If the wire is not contacting properly, it may be
   necessary to remove the wire, add more holes and then get
   a longer wire and thread it through again.

* The control key does/does not work, but various other keys no
  longer work either.

   This could happen because you have inadvertantly damaged other
   tracks on the mylar while attempting the repair. If this is
   the case, you could try repairing these other tracks as well,
   although it might end up easier to just buy a new mylar.

   This may also happen because one of the ribbon cables is not
   inserted correctly and fully in its socket.

* The control key causes random characters when pressed.

   This happens when the wire you added is making electrical
   contact with the metal keyboard backing. Ensure that
   insulating material is present between the wire and the
   backing so that electrical contact cannot occur.


CONCLUSION

If you have carried out the repair, chances are you now have a
working control key. Congratulations!

If, however, the repair was unsuccessful, you may attempt to
rectify the fault yourself. Provided you carried out the repair
as described, I do not believe there is much that can go wrong.

I do not want to receive huge amounts of email from people who
have problems with this repair. You carry out the repair at your
own risk. If you do need to contact me for some reason, however,
my email address is given at the bottom of this document.

Good luck!

--
Mario Becroft
mb@tos.pl.net
http://www.pl.net/user/mario/