Need to fix hole in ribbon cable

[Francis McGrath]

I have a flat ribbon cable in a synthesizer that senses pressure
aftertouch. It lets you play a note, then push harder on the key to
get an extra effect. Well, I put a screw through it. I'd like to
repair it because it's easy to get to the hole, but really hard to
remove the whole cable. The problem is that I don't know what kind of
wire it is or how it works. Since I don't know what it's called, it's
hard to do a google search. I've posted a picture of it at
http://www.francismcgrath.com/wire.jpg. Can someone tell me what this
kind of wire is called? Secondly, I'd be very interested in learning
how to fix it.

Thanks, Francis

 

[hr(bob) [email protected]]

I have a flat ribbon cable in a synthesizer that senses pressure
aftertouch.  It lets you play a note, then push harder on the key to
get an extra effect.  Well, I put a screw through it.  I'd like to
repair it because it's easy to get to the hole, but really hard to
remove the whole cable.  The problem is that I don't know what kind of
wire it is or how it works.  Since I don't know what it's called, it's
hard to do a google search.  I've posted a picture of it athttp://www.francismcgrath.com/wire.jpg.  Can someone tell me what this
kind of wire is called?  Secondly, I'd be very interested in learning
how to fix it.

Thanks, Francis

How many conductors are there in the cable, and do you know how to
solder?

 

[Francis McGrath]

How many conductors are there in the cable, and do you know how to
solder?

Thanks for posting.

There are 2 wires that come out of the blue connector, so I guess that
means 2 conductors. That's part of what makes me confused, there only
appears to be one cable zig-zagging through the wire, but on closer
examination, the zig-zagging part is clear. And yes I can solder.

Francis

 

[IanM]

Thanks for posting.

There are 2 wires that come out of the blue connector, so I guess that
means 2 conductors. That's part of what makes me confused, there only
appears to be one cable zig-zagging through the wire, but on closer
examination, the zig-zagging part is clear. And yes I can solder.

Francis

It looks like some sort of capacitive sensor. I don't think the QTC type
of pressure sensor can be made clear like that. You have lost three of
the 'fingers' but there is no damage to the main conductors. Also from
the diagonal crease, the damage would appear to be between the keyboard
and the circuit board, *NOT* under any keys.

YOU GOT LUCKY!

Just take a very sharp craft knife and trim the edges of the hole
carefully taking off as little as possible to remove any fragments that
might short-circuit, but *DO* *NOT* nick or cut the main conductors top
and bottom. It should still work just fine. If the crease is your
doing, and the hole is under a key try it anyway but it may need to be
adjusted sideways slightly so the hole falls between keys. If the hole
is in contact with any metal surface when installed put a bit of
insulating tape on the metal to prevent contact (not on the hole, the
'sticky' may cause problems when it ages).

 

[hr(bob) [email protected]]

Thanks for posting.

There are 2 wires that come out of the blue connector, so I guess that
means 2 conductors.  That's part of what makes me confused, there only
appears to be one cable zig-zagging through the wire, but on closer
examination, the zig-zagging part is clear.  And yes I can solder.

Francis

It looks like some sort of capacitive sensor. I don't think the QTC type
of pressure sensor can be made clear like that.  You have lost three of
the 'fingers' but there is no damage to the main conductors.  Also from
the diagonal crease, the damage would appear to be between the keyboard
and the circuit board, *NOT* under any keys.

YOU GOT LUCKY!

Just take a very sharp craft knife and trim the edges of the hole
carefully taking off as little as possible to remove any fragments that
might short-circuit, but *DO* *NOT* nick or cut the main conductors top
and bottom.  It should still work just fine.  If the crease is your
doing, and the hole is under a key try it anyway but it may need to be
adjusted sideways slightly so the hole falls between keys. If the hole
is in contact with any metal surface when installed put a bit of
insulating tape on the metal to prevent contact (not on the hole, the
'sticky' may cause problems when it ages).

--
Ian Malcolm.   London, ENGLAND.  (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL:- Hide quoted text -

- Show quoted text -

But if the hole cut thru any of the conductors, like it appears to do,
the OP will have to reestablish continuity by soldering a wire to each
end of the broken path to reestablish the continuity.

 

[IanM]

On Jan 1, 10:46 pm, "hr(bob) [email protected]" <[email protected]>
wrote:
I have a flat ribbon cable in a synthesizer that senses pressure
aftertouch. It lets you play a note, then push harder on the key to
get an extra effect. Well, I put a screw through it. I'd like to
repair it because it's easy to get to the hole, but really hard to
remove the whole cable. The problem is that I don't know what kind of
wire it is or how it works. Since I don't know what it's called, it's
hard to do a google search. I've posted a picture of it athttp://www.francismcgrath.com/wire.jpg. Can someone tell me what this
kind of wire is called? Secondly, I'd be very interested in learning
how to fix it.
Thanks, Francis
How many conductors are there in the cable, and do you know how to
solder?
Thanks for posting.
There are 2 wires that come out of the blue connector, so I guess that
means 2 conductors. That's part of what makes me confused, there only
appears to be one cable zig-zagging through the wire, but on closer
examination, the zig-zagging part is clear. And yes I can solder.
Francis

It looks like some sort of capacitive sensor. I don't think the QTC type
of pressure sensor can be made clear like that. You have lost three of
the 'fingers' but there is no damage to the main conductors. Also from
the diagonal crease, the damage would appear to be between the keyboard
and the circuit board, *NOT* under any keys.

YOU GOT LUCKY!

Just take a very sharp craft knife and trim the edges of the hole
carefully taking off as little as possible to remove any fragments that
might short-circuit, but *DO* *NOT* nick or cut the main conductors top
and bottom. It should still work just fine. If the crease is your
doing, and the hole is under a key try it anyway but it may need to be
adjusted sideways slightly so the hole falls between keys. If the hole
is in contact with any metal surface when installed put a bit of
insulating tape on the metal to prevent contact (not on the hole, the
'sticky' may cause problems when it ages).

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL:- Hide quoted text -

- Show quoted text -

But if the hole cut thru any of the conductors, like it appears to do,
the OP will have to reestablish continuity by soldering a wire to each
end of the broken path to reestablish the continuity.

The OP stated (*EMPHASIS* added by me):

The zigzag is clear and is extremely unlikely to be a conductor. There
are two contacts described at the blue end. I therefore concluded the
white/silver strips with interlocking fingers were the conductors, which
would suit capacitive proximity sensing. *NOTHING* will need bridging
and soldering that sort of cable *will* destroy it unless the OP has an
extremely delicate touch.

 

[IanM]

Your a better solderer than I if you can solder to plastic!!!!!

Been there, done that. Sinclair keyboard cable repairs. It can be done
but the success rate per joint is sufficiently low that repairing
anything complex is totally impractical, You need *extremely* flexible
wire to stand a chance of it working and even so the repair is
incredibly fragile. Also its 'kill or cure' as the slightest mistake and
you've melted through the plastic. I'd rather clean a swimming pool
with a toothbrush, it would be less frustrating . . .

 

[Andy]

I have a flat ribbon cable in a synthesizer that senses pressure
aftertouch. It lets you play a note, then push harder on the key to
get an extra effect. Well, I put a screw through it. I'd like to
repair it because it's easy to get to the hole, but really hard to
remove the whole cable. The problem is that I don't know what kind of
wire it is or how it works. Since I don't know what it's called, it's
hard to do a google search. I've posted a picture of it at
http://www.francismcgrath.com/wire.jpg. Can someone tell me what this
kind of wire is called? Secondly, I'd be very interested in learning
how to fix it.

Conductive paint?

 

[Francis McGrath]

I want to thank everyone for posting. I want to make sure I
understand what everyone is saying. There are 2 "wires" with little
teeth. Each wire looks like:

____________________
| | | | | | | | | | | |

It looks like I damaged some teeth, but not the main part of the
wire. Yet it's still not sending signal. Does every tooth have to be
there?

Something I else I'm wondering, since the damage is near the end of
the cable, could I just cut off the damaged portion and reattach the
connector? I have enough slack for this. If I try to remove the
connector, it will probably ruin it, won't it? Also, I don't know how
the ribbon cable hooks to the connector. Any thoughts?

Thanks again, Francis

 

[IanM]

I want to thank everyone for posting. I want to make sure I
understand what everyone is saying. There are 2 "wires" with little
teeth. Each wire looks like:

____________________
| | | | | | | | | | | |

It looks like I damaged some teeth, but not the main part of the
wire. Yet it's still not sending signal. Does every tooth have to be
there?

Probably not, especially if this part isn't under any keys. Just to
eliminate the more insane possibilities, can you confirm that this cable
is only connected at one end?

Something I else I'm wondering, since the damage is near the end of
the cable, could I just cut off the damaged portion and reattach the
connector? I have enough slack for this. If I try to remove the
connector, it will probably ruin it, won't it? Also, I don't know how
the ribbon cable hooks to the connector. Any thoughts?

If you powered it on with the screw through the cable, its possible you
damaged the circuit that this sensor connects to. Its also possible you
have a short circuit in the cable due to the damage, but I don't think
so looking at the photo. Is there any evidence of damage to the blue
connector or the mating socket caused by the cable getting pulled as the
screw went through it?

Its likely the contacts on the cable were crimped in place and then the
blue plastic was either moulded round it or otherwise bonded. I wouldn't
try dismantling it without a quote for a replacement in front of me. If
it is a capacitive sensor, shortening it by more than a very small
percentage of the total cable length may put the circuit out of
adjustment and prevent it working anyway.

Check the resistance across the two contact pins on the cable with it
disconnected from the board. If my suspicion that its a capacitive
sensor is correct, the resistance should be higher than a good
multimeter can measure. In that case, connect a capacitance meter, and
see if the capacitance changes noticeably when a small metal object
(e.g. a coin taped to a biro to let you move it without getting your
hands near the circuit) is placed against the cable surface. You will
probably only get a change of a few picofarads. Try either side of the
damage.

I think that it probably calibrates the sensor when it's switched on and
if you allow the cable to move while you are testing the complete unit
it may go out of adjustment and so not work. Did you try it out with the
lid *ON* (you don't need to put all the screws back in)?

Also what was the fault or reason that made you open it to start with?

 

[Franc Zabkar]

WHat you have looks like a rectilinear sensor.

I used to work for a company ( www.spectrasymbol.com ) that used to make
these similar types of parts. They are actually silver and carbon
conductive elements that are silkscreened onto plastic. You cannot solder
this. It called a"Linear Potentiometer" or "Flexible Printed Circuits" or
"Membrane Switch Technology" Remeber the old Atari 400 Keyboards?


The connector is a form of a BERG connector
http://www.bergelect.com

I can see how the membrane pot works ...

http://www.spectrasymbol.com/typo3/site/en/softpotsplash/how-it-works.html

.... but how would it sense pressure?

The OP's cable appears to have two adjacent conductors with
interlocking fingers. If the cable was a Hotpot, wouldn't both
conductors need to be directly above each other?

- Franc Zabkar

 

[Francis McGrath]

OK,

I decided to take apart the connector. The blue part was just a
plastic holder. Inside were 2 metal pins hooked to each side of the
cable. For lack of a better term, they were basically stappled into
each of the two "wires". Seeing how it was connected, I got
inspired. I bought a connector like you see at the end of an IDE
connector. This one had 8 pins, so I removed 6 of them. I cut off
the wire and discarded the portion with the hole in it. I was able to
punch the pins through the wires just perfectly but it still didn't
work. So it's starting to look like there is a problem somewhere else
in the wire.

Since getting taking the wire out would involve literally hundreds of
screws, I'll wait till I have to go in the keyboard for some other
repair. I guess I can live with it for now.

Thanks to everyone for their great advice.

Francis