[sdiy] D-70 red goo of death

[Dave Brown]

I have a D-70 with the red goo of death.  Keys are stuck together, the
weights are falling off the keys, and it’s dripped all over the PCB and
rubber keypad strips.  Some of the keys stopped working so I took it apart. 
You have to disassemble most everything to get the keyboard out.

I can’t find anything that dissolves this goo.  Lacquer thinner softens it a
bit, but also everything else.  Acetone doesn’t touch it at all.

The keyboard PCB is made up of two flex circuit boards with encapsulated
diodes and carbon key button pads.  I think the goo has probably destroyed
some of the runs.  To make matters worse, this flex circuit board is
press-fit to another flex circuit board which wraps around to a connector to
a flex cable to the control PCB.  Where the two flex circuit board pads were
pressed together the one stuck to the other so now all the edge pads are
missing (well, really they are stuck on the other flex circuit board).  I
have to believe there are probably microcracks as well.  The only way to
really test this is put it all back together and see if the keyboard works. 
I’ve done that once and ended up with 4 that didn’t function.

At this point, even if I could repair the traces, I assume the red goo will
continue to soften and drip.  Right now I’ve put it all back together
without the keyboard and am using it as a MIDI synth module.  It isn’t that
great of a synth with only 64 presets but I hate to send it to a landfill.

Has anyone found a way to clean up this red goo?  My web search results all
say no one has yet.

Any thoughts on repairing the traces on the flex circuit board?  I would
need some conductive paint that I could paint over the runs.  It does look
like except for the keypads it has a mask on it so I would have to try and
remove that without removing the traces in order to repair them.  Who has
had good results with conductive paint and what did you use?

I just hate junking old electronics.  I’ve even thought about repackaging it
into a rack unit but the synth just isn’t worth the effort.

Who do you suppose picked this red glue that really isn’t a glue.

David J. Brown
Email davebr at earthlink.net
Website http://modularsynthesis.com