[sdiy] D-70 red goo of death - not epoxy, maybe polyurethane

[Dave Brown]

I heated up some water in a glass jar in the microwave (I'll have to get a
junk pan to do this in).  I went up to about 150 degrees F.  It softens the
goo enough that you can scrape most of it out.  If there was a weight still
in the key, then you can pry it out with a small screwdriver.  Then you can
dunk the key again and soften the goo and scrape the rest out.

The metal weights are a mess but I can put them in a pan and boil them.  I
think that will work pretty good.  I will have to have a second pan because
they are so sticky you can't set them down on anything.

I'm still left with a film all over the inside of the key.  I tried
reheating it and then using a Q tip but the cotton just sticks to the
remaining goo.  Just for fun I poured some baking soda into the water and it
reacted and I got some crud floating on top.  I immersed the key in again
and used the Q tip and I could clean the key out really well.  It isn't
perfectly clean, but clean enough that nothing will ever drip out and it
looks fine.

I tried gluing one weight in using silicone.  I think that will work nicely.
The issue is I have to do this 60 more times!    I think the film floating
on the water will preclude doing more than a few keys before I have to
change the water.  It stays hot enough long enough that I think I can just
use the microwave to heat it up.

I still need some tips on silver / carbon paint.  I can find some silver
epoxy, but I am not sure I want that.  I'm thinking of something I can mask
and then paint back on.  I did find these at Mouser but Ouch at the price.

590-8420-P Chemicals SILVER CONDUCTIVE PEN 0.3 oz $23.01
590-842-20G Chemicals SILVER PRINT 20G ( 3/4 oz) LIQUID $45.02

Dave

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Dave Brown
Sent: Monday, January 28, 2013 3:25 PM
To: 'Bob Weigel'; synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] D-70 red goo of death - not epoxy, maybe polyurethane

I think I agree with this.  The synth isn't worth the hassle of dealing with
harsh chemicals and possible accidents.  The goo does soften at fairly low
temperatures.  I found I could get it off the flex circuit board by heating
it up with my hot air gun, scraping the excess off, and then cleaning it up
with a Q tip and lacquer thinner.  Lacquer thinner tends to dissolve the goo
when it is more fluid when hot.

I think heating the keys in water may be a good way to go.  With the hot air
gun I can soften and scrape the stuff out of a key where they weight has
fallen out.  With those keys with the weights still in them I don't think
this would work very good.  The issue with heating in water will be to make
sure the soften goo doesn't get all over the keys.

So, I am now left with how to repair the flex circuit boards.  There are two
small sections where the traces are damaged.  I assume these are a thick
film paint so I probably need something to paint over them.  They look like
possibly silver-based.

At the edge connectors the silver traces went to the edge (and are no
missing) and then had a thicker coating over them to form the actual
contact.  I assume I would want to paint down a silver higher conductivity
paint and then layer over that a thicker carbon/black coating.

I haven't looked yet for conductive paints.  Any suggestions for a high and
medium conductivity paint?

Dave

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Bob Weigel
Sent: Monday, January 28, 2013 2:49 PM
To: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] D-70 red goo of death - not epoxy, maybe polyurethane

I've usually just peeled the stuff off of keys when it gets away but I've
never had to clean up the whole mess...but seems to me you could just put it
in hot water that isn't hot enough to deform the keys.  This stuff melts at
around 110 degrees F or so I think since it melts in the air at temps near
that.  Don't boil it for sure, that warps the keys. 
I've heard of people doing that.  lol.  But when you get it warmed up the
weight should come out and clean all the adhesive gel off with a scrubber or
whatever and that should be the easiest I'd think.



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