Fix for squeal on Casio digital horn DH100? [Archive] - Sax on the Web Forum

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basil b.
12-09-2004, 03:07 AM
Does any one know how to get this thing to quit squealing? From what I've heard it's a common problem. It's a midi controller breath driven, cheap copy of a yamaha.


Bill Mecca
12-09-2004, 03:19 AM
google it.
I know there are a couple places out there that have posted instructions. I found them a while back while looking at an ebay auction for one.

they have their fans, and I do remember the squeal being a common problem.

12-09-2004, 04:53 AM

Bill Mecca
12-09-2004, 07:14 PM

12-09-2004, 07:31 PM
Not a bad return for a 50 cent part replacement. :shock:
Now, where did I put my mini-torch?

basil b.
12-10-2004, 01:29 AM
Thanks you guys for coming through once again, and to guys like dorian who post helpful info without trying to make their own private idaho.

This is a repair I think even I can handle, now that I know which little do hicky is the culprit.

Bill Mecca
12-10-2004, 03:44 PM
I hadn't come across the dorian site, i posted the first one I found. :oops:
good to know some out there are passing along that kind of information. I did find something similar for the Zoom PS-04 multi track recorder, it has a similar problem and some one has posted a fix on the web. (basicially you need to shield parts from each other, which Zoom should have done in the first place)

Andy A1S
06-07-2013, 03:22 AM
The Dorian Rose link doesn't work any more, unfortunately. In case anyone else is looking for this information, the best resource is Paul Fox's Casio Horn page:

- The squeal fix is towards the bottom of the page, under "HOW TO FIX THE SQUEAL (DH-100 and DH-200)". He also says how to adjust the breath sensor, and fix a couple of other possible problems.

He doesn't actually say which end of the 33uF electrolytic capacitor is which, but the negative terminal goes to the thicker track, toward the bottom of the picture. On his example, that side of the cap is marked by a thick black line, and most electrolytics probably are marked that way.

I used a tantalum bead capacitor, because they're supposed to last better. Those always seem to have the positive terminal marked instead, often with a black vertical line, and a + sign.

Another good resource is

He offers Casio horns for sale (in the US), and does repairs. He also gives details of how to add the missing Eb key to a DH-100:

I've done a variation on that, "borrowing" my portamento key to make the Eb, and moving the C key down, swapping the longer rod from the right hand keys with the shorter one from the left hand keys.

I had to make two new holes for the Eb and C keys to go through, and a new hole to the top rod support post (substitute your own technical term). I used a flattish PCB mounting push button for the C, gluing it to the PCB that holds the key contacts, with the legs bent up so they sit above the PCB.

The clear plastic inner part of my new Eb key only made contact with the edge of the rubber bit that presses down on the contact, so I replaced it with two cut off bits of plastic from servo arms, glued together with Contacta (a kind of polystyrene cement - plastic model glue), to make a longer reach.

It would be fairly simple to add one or more side keys, by the same principal - add some more push buttons and run wires to the contacts PCB. For the usual three side keys (four if you count F#... five with high F#) you could just wire them all to the left hand pinky key - used in their proper context, all three are sharp keys (e.g. side Bb is really A#).

If anyone's interested, I'll post pictures of my modded DH-100, but it looks pretty similar to the tedkeys one, just without a portamento key. He used a spare long rod and key, but I had to just swap mine around.

Andy A1S
06-13-2013, 10:26 AM
Here's another great "squeal fix" and general Casio DH-100 resource - scans of the service manual, from Electri-fire's Site:

If you want to go further than just fixing it, Kerry Bradley's site has some promising mods to suppress the vibrato (on older models only), drop another octave lower, and add a resonance control (expanding on what's already provided, so fairly simple looking):

Somewhere, on my quest to learn about the squeal problem, I downloaded a nice clean image of the fingering chart from a scan of the user manual, in two pieces, and pieced them together. If I remember where, I'll add a credit.

For want of somewhere better to put it, I'm attaching it here. If you download it, you'll need a decent image viewer, like , to make it comfortable to use.


It's actually two fingering charts in one. The top row is the woodwind style fingering chart, which is fairly saxy, with just a hint of flute. The lower row is Casio's own, truly bizarre, fingering system, which bears some resemblence to EVI fingering (Electronic Valve Instrument, for electric trumpets, and so on), but the main three trumpet fingers covers an octave without the accidentals, rather than a fully chromatic fourth.

Andy A1S
06-13-2013, 10:33 AM
I see the forum engine has compressed that fingering chart image and made it all blurry... I tried attaching it as a zip, but there's a 200KB limit, and it still doesn't fit. I've tried converting it to a GIF, which roughly halves it, and zipping that, but that doesn't help either :(

If anyone wants it, without the blurriness, pm me...

Okay, I've tracked down where I found the original two piece charts. The page is only available via the "Wayback Machine", i.e., the original page doesn't exist any more, but it's been archived:

I expect more of these pages will start to disappear, so it's worth saving them while you can. Here are those two images, for posterity, hopefully not ruined by re-compression this time.


If you click on the link, then click each image, you'll see an even clearer one, but they're bigger, so there's no way I can attach them here.

Andy A1S
06-18-2013, 11:01 PM
but the main three trumpet fingers covers an octave without the accidentals, rather than a fully chromatic fourth.Oops. Should say perfect fifth?