Casio DH100

in 1988 Casio introduced the DH-100 (DH stands for ‘Digital Horn’ ) as the first in a series of Saxophone-shaped and windwood-sounding  that offered their kind of yamaha breath controlled synth.  The sax works with both batteries (5 AA) or a wall wart of 7.5 - 9 with center negative. It has a 1/8” output jack, but will play thru internal speaker.

A greek tour

A very nice tour in Greece during summer 2022, great country, very nice people. It was however quite a rough job to help all stray cats there, and sometimes quite painful, but this is another story.

Visiting Thessaloniki, I could not resist to visit a local flea market with some antiques store maybe to bring back a bouzouki home. Lots of guitar,weird stuff around, but I finally managed to find something out: a Casio midi saxophone called "DH100". Not really greek, but I could not resist. Quite in nice shape, the seller told me it was working. Was it true?

What's wrong with it?

No, it was not true! The Horn simply does not switch on, on both batteries and external PSU. 
Found out the service manual and schematics (download at the end of this page). There are many technical information about the repair, but it' mostly about leaking capacitors for a kind of squeaking sound out of the device,but we will see that later.
So, it's time to grab the screwdriver, and open up the guts- it's quite easy to open with a a few screws (do not touch the ones on the battery slot,it's unnecessary).

The dh100 just split in 2 main parts: two main boards one for sound digital generation and another analog for connections, voltage regulation and Midi interface logic.

UPPER At first glance, not much, all seems in good shape. All voltages are there, desoldered the ribbon for easy access to lower board to check it. Time to flip it 

UPPER  - The horror! a totally corroded board around the jack output. Does not seems battery (the slot was ok) nor capacitors that are on other board. Maybe some water? ouzo? anyway, it is time to clean up that mess.

UPPER After cleaning and inspected all tracks, the dh100 still not fires up. Strange, mumble. Since all mess is around the audio output I tried to connect an headphones and ... sound is there. How stupid Am I: I assumed it was not working due to LED not switching on (in fact it is dead). Ok , but for some reasons there is not sound on the internal speaker. Looking again at the cleaned part, I found an interrupted track going to speaker. Quickly repaired the track, the Speaker star to make something out of it.

Fooled by a diode

As I suspected it was simply the diode led not working anymore, so I replaced it with a maybe a little too short one, but at least you can see when it's switched on.

I think it should be all good, maybe I take advantage of the opportunity to change that famous SMD electrolytic capacitor to prevent the squeal on the other board. To be honest the other SMD ones does not have a good ESR, anyway, they seem to be pretty clean around.

UPPER: The  (C39 which is 33uF) is replaced with a T-H standard capacitor with higher Voltage. You just have to bend it a bit, I just insulated it from the board for security. Anyway, I think I will soon have to replace the others.

Reassembling and testing

And quickly reassembling, all seems to be in order. Tried all 6 sounds, all buttons are working. It seems to be pretty funny using it as Midi controller.
Casio DH100 RESET PROCEDURE:  none
If you need it, here's the english and other languages  and here the SERVICE MANUAL 

Original buttons/interface:

Portamento key to glide between notes for a kind of glissando effect.
Tone Select button which is the original patches (cannot be edited) of the instrument: Sax, Trumpet, Synth-Reed, Oboe, Clarinet and Flute.
Key Select to change range of pitch, for transposing.

Midi Out supports only the played notes, portamento and breath pressure values are sent.
Breath On/Off varies the style of play so that sounds only come out when modulated by breath control (ON) or whenever a set of keys are pressed without breathing (OFF).
Volume control 

Other models from the family:
-DH-200 same but v
-DH-500 Added additional keys to satisfy actual Saxophone players. 
-DH-800 same as 500 but with included ROM packs to play along with


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