Casio Horn E-Flat Key Mod

One of the things I have most disliked about the DH-100 is that Casio left off
the E-flat key that Sax and flute players are accustomed to. In the interest of
saving a little money, the function that would normally be filled by the
right-hand little finger was moved to the left-hand little finger. It is not too
hard to pick up the new fingering, but I never really got comfortable with it.
And a few times, I found myself using the Casio fingering on a real sax, which
of course doesn't work.

I got to wondering how hard it would be to add the missing key. I actually
thought about this off and on for several years, but it always seemed like too
much trouble. I envisioned laying out out a new circuit board, fabricating keys,
figuring out how to mount it, etc. Turns out it wasn't all that hard. Using
spare parts from my boneyard of old Casio horns, I was able to install the
missing E-flat key. I am thrilled with the result.

Here are the basics of how the mod was accomplished. It doesn't really give
enough specific detail, but it does give the general idea.

Parts required from an old horn:

Shaft that holds the upper keys. This shaft is longer than the one that
holds the lower keys and provides room to mount the new key.

Some of the spacers from the upper key shaft. The new shaft is actually
too long and these spacers fill in the extra space.

The right-hand little finger key. This key becomes the new low-C key. The
old low-C key is rewired to be the E-flat key.

The key circuit board. You have to cut one of the contacts off of this
board and glue it in place to provide the contact for the new key.

One of the elastomer key contact strips. You have to cut one of the rubber
buttons off of this strip and secure it over the new contact.

The basic idea is to install the new key on the new longer shaft and drill a
hole in the case at the right spot for the new key. The new contact is glued
onto the contact circuit board. Because the new contact is raised 1 pcb
thickness higher than the other contacts, I sanded down the button actuator by 1
pcb thickness.

The rubber button has to be secured over the new contact. This is tricky,
because the silicon rubber elastomer has a very low surface energy, meaning that
there is virtually no adhesive that will hold it in place effectively. I ended
up drilling small holes in the contact circuit board and wiring the rubber
button into position, essentially 'stapling' it in place.

The only thing left to do is rewire the bottom two keys. The ciruit trace to
the old C-key is cut and the old C-key is wired in parallel to the left-hand
little finger key. The new key is wired in in place of the old C-key and becomes
the new C-key.

Assemble and play!

Inside shell of the DH-100 with the contact PCB removed. The
new key actuator can be seen just left of the grey contact strip.

The contact PCB with the new contact glued in place. The new contact is
cut from another contact PCB.

A rubber contact button that has been cut from a longer strip is
visible above the PCB.

This page was last updated on 21 February, 2006. Copyright Ted Keys
2006