[Premium-Rx] R3030A keyboard debounce

[refmon]

Hi,

Possible breakthrough here!  Read on.  Looking at my manuals for 3030A vs
3030, they show identical drawings for both Panel Interfaces...the base
drawing dates are the same 1984 date... however, there are a bunch of ECN's
spanning 4-1-85 thru 4-11-86...but that's not it...the ECN's mostly update
drawing references and fix typos...now the good part:

The module is 2140-1116, the circuit board is 2140-2018, and the schematic
is 2140-2418...notice there's no A, B, C shown.

Tucked up in the corner of the drawing are rev A and rev B.   rev A is not
related.  Rev B states that C2 was changed from 3.3uf/15V to 10uf/20V as of
date 3-8-85.  C2 is on pin 7 of U6, the keypad encoder.  The keyboard
encoder is a 74C923.  Search 74C923...look at "ext C" on the data sheet
internal diagram... the external C is none other than KEYBOARD DEBOUNCE!!!

Now the mystery:  although my R3030A was made prior to the revB date, it has
a revB circuit board inside.  However, C2, which for some ungodly reason is
potted in shoe goop or some other potting substance, is color coded orange
up top and green lower down on the bottom where the wires come out...it's a
tantalum.  I'm rusty on this, but I decode those colors to be 3.3uf.  PLEASE
DOUBLE CHECK me on that.  Unfortunately, I cannot see any printed info on
the body of the cap.

I am up for some field surgery...does anyone know what will dissolve the
potting stuff without eating the components and board?

Based on my findings thus far, I have not opened any of my R3030
modules...I'm trying to keep them sealed...I suspect, though, that the 3030
has the 10uf update in place, as its manufacture date stamps are from 1986.

read this over....double check my decode on the colors, pry off the module
covers on your receivers and see what you've got.

regards

John
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