Paul Fox's Casio
Horn Page

(Launched 16 November 2003. Last update 29
November 2005)

These are CASIO Digital Horns: DH-100
(silver) and DH-200 (black). Made in the late 1980's, they can be used
independently (with six different built-in voices) or used as a breath
controller for any MIDI synthesizer.

Does your horn squeal? Dorian
Rose has a webpage showing how this fault can be fixed easily. Go to http://www.btinternet.com/~dorian.rose/
and mail your thanks to Dorian when your horn is fixed.

BIG NEWS!
Want to know how to turn off the vibrato? Kerry Bradley has a webpage that will
show you how. Go to http://home.earthlink.net/~kerrybradley/id1.html
for details.

My pages are about fixing other
problems. So far I have published fixes for three:

BREATH
SENSOR ADJUSTMENT

NO
SOUND (due to a damaged clock pulse circuit).

NO
SOUND WITH BREATH MODE ON

Click on the links or scroll down for details. Email me to ask about other
faults. I have other fixes that I haven't published
yet.
Information on
these pages is provided free, but if it has helped you with anything other
than the squeal fix or the vibrato modification, you may like to:

Do you have a broken horn? I may be able to
help, or I might be interested in buying it for spares if it's beyond repair.

I also have a small stock of SPARE PARTS: keys, springs, tubes and other
internal parts. Email me to ask if there's something you need. Sorry but I
don't sell mouthpieces.

By the way, I'm in England. If you're in the USA and need a horn repaired,
take a look at Ted Keys' website. Ted
knows more about these things than anyone I know, and he's fixed loads of them.
He's a genuine nice guy too.

I'VE GOT LOTS OF INFORMATION ABOUT THESE THINGS THAT ISN'T ON
THE WEB PAGE YET.

NEED AN INSTRUCTION MANUAL OR FINGERING CHART? I HAVE THEM IN
ENGLISH, SPANISH, FRENCH, ITALIAN, DUTCH AND GERMAN - PHOTOCOPIES AVAILABLE FOR
COST OF COPYING AND POSTAGE.

You can email me about problems, fixes or anything else to do
with Casio horns at: mailto:[email-masked]

Let me know if the information on this page has helped. I Look
forward to hearing from you!

So far, 29 horns have been fixed thanks to these
pages.

DISCLAIMER: THE
ADVICE GIVEN ON THESE PAGES IS TO BE TAKEN AT YOUR OWN RISK. I AM NOT AN
ELECTRONICS EXPERT, THIS IS JUST A HOBBY FOR ME. I AM JUST SHARING THINGS I'VE
FOUND TO WORK, BUT I CAN'T BE HELD RESPONSIBLE FOR ANY DAMAGE CAUSED THROUGH
ATTEMPTING THE REPAIRS / ADJUSTMENTS GIVEN HERE.

BREATH SENSOR
ADJUSTMENT.
If the sensor is adjusted
correctly, you should get a graduation in volume, from very quiet to very loud,
when the volume is turned up fully. The sensor should be very sensitive to
changes in breath pressure. If the sensor is NOT adjusted correctly, you may
feel you have to blow very hard to produce a note, and that the horn only plays
quietly. This is probably caused by a badly adjusted variable resistor (VR) on
the circuit board.

Check the breath mode switch is in the ON position. Remove the mouthpiece and
the six screws holding the two horn shells together (one of these is in the
battery compartment). You'll need a small cross-head screwdriver to remove the
six screws . You'll also need a small flat-bladed screwdriver to adjust the VRs.
With the horn open, you will see two circuit boards stacked inside the back half
of the horn. The top board, labelled M263-MA1M, has two variable resistors on
it, labelled VR1 and VR2. These should be easy to find, there's no need to take
the horn apart any further (See photo below.)

(The ceramic resonator is labelled for
the next fix; for now you're just interested in VR1 and VR2.)

To reset the breath sensor to factory settings,
follow this
link.

To adjust the sensor by ear, use the following instructions:

To begin with, leave VR1 at its current position.
Power up the horn and turn the volume up FULL. (You'll be listening for sound
and silence, and you'll need to know when the horn is really silent). There are
2 ways you can adjust VR2.

EITHER:

Blow hard into the tube and adjust VR2 until the horn is playing its loudest.
(It's a bit tricky with the horn in pieces held together by cables, but you'll
soon get used to it.) Stop blowing and the horn should be silent.

OR:

Adjust VR2 until the horn starts to produce a note without any breath, then
back off slightly so it's silent again.

In both cases, you shouldn't need to alter VR2 by
more than half a turn.

Try blowing the horn again, and you should find that you have a full range of
volume and sensitivity. If you think it should still be louder, try small
adjustments of VR1 to see what effect it has, until you're happy. (Basically VR2
sets the threshold between "no breath" and "breath", and VR1 controls the
maximum voltage that is passed into the analog/digital converter in the CPU.
Email me mailto:[email-masked]
if you want more details.)

POWER BUT NO
SOUND.

I came across this in one horn, and the fault was
obvious when I examined the circuit board.

Symptom: the horn powers up, the power light stays on and you can hear a
quiet background hiss in the speaker (if the volume is turned up full.) This is
normal. However the horn would not produce a sound, either with breath mode on
or off.

The problem: a damaged component. The 12 MHz crystal on the board M263-MA1M
had been broken. This looks like a blue ceramic capacitor (see top photo) and is
part of the clock pulse circuit for the CPU. Without the circuit producing a
clock pulse, the CPU won't do anything. I desoldered the legs and removed the
parts of this component.

The board with the resonator
removed.

Casio's specification for this component is
"CSA12.0MT18". It's a ceramic-encased crystal with a frequency of 12.0 MHz. I
couldn't find a ceramic one but I managed to get some crystals housed in cans
(see photos). I tried both of these unsoldered and they both worked, so I
soldered the small one in place and trimmed off the legs.

An original ceramic crystal (blue) with
two different style "cans"

The repaired board in a
DH-200

INCIDENTALLY, I also tried a 4.0 MHz crystal instead
of a 12.0 MHz one. As you might expect, the horn worked perfectly but the pitch
was much lower. Normally the base note of the horn when it's first switched on
is Middle C, but with the 4.0 MHz crystal it was a low F, about one and a half
octaves lower.

NO SOUND WITH BREATH MODE
ON.

Thanks to Martin in Germany for working this one out
and sending pictures of his repair.

[Please note, I haven't performed this repair myself yet, but will try to
give more details when I have. For now, here's the basic information.]

Symptom: WIth the Breath Mode switch set to ON, the horn makes no sound when
you blow into it, but with the switch OFF the horn plays when you press the
keys.

The problem: a damaged component. The transistor T6 has failed. This is a
small surface mounted transistor, at the top right of the board when you first
open the horn up. It can be replaced with a BC547 for just a few pence.
Unfortunately it has to be soldered onto the board surface, there are no
convenient holes to use. Bend the legs into an 'L' shape to get a good contact
on the pads on the board. Adjust the sensitivity as described above when the
repair is complete.

BC547 transistor.

BC547 in place.

If this information has helped you,
please let me know at [email-masked]