Casio DG-20, headpiece mech

Advancing with the DG-20 repairs..  Against my initial plan of “covering the rest of mech stuff at once”, the focus this time will be entirely on fixing the damaged headpiece mech. It turned out that some previous owner of my DG-20 has been kind enough to remove the fretboard rubber mat by tearing it off and attaching it back with some “hard plastic” type glue. Sooo.. because of this the rubber mat is in three pieces (instead of one) and there’s a neat glue mess waiting to be cleaned off the fretboard, all adding up to a bit of extra repair “fun” for me. Thanks a bunch.

These here are what this post is about, the DG-20 headpiece string tuning mech. A complete original part above and the damaged below it.

Figured I’m probably faster off describing this mech stuff with images and thus took detailed workstep photos. Too bad that I forgot to disable ‘save as grayscale’ setting when editing/saving the following photos and noticed this only after upload/editing everything ready for this post! No way I can’t be arsed to edit/upload everything again, so you get to suffer “artsy grayscale”  this time around ;). If you have a DG-20 in need of similar repairs and wish to take the DIY route, you will need the following tools and parts:

• A vertical (press) drill
• A 3mm threading tool
• 2.6 mm metal drill  bit
• A lathe (!)
• A metal saw and a file OR a miniature power tool equipped with a (circular) metal cutting blade.
• Matching amount of M3*35 screws and M3*28 standoffs.

Great thing (at least for me) is, the mech designer(s) responsible for DG-20 have opted to use metric items on the headpiece mech. 3mm diameter/threading is used in the stock part, thus finding replacements is easy.

Step 1. Drill a hole to headpiece mech using a 2.6mm bit.

On the picture above, I’m using a thick piece of aluminium under the part. Since it’s a bit too small to clamp down properly just by itself, the extra piece provides drilling support.

Step 2. Thread the resulting hole for a 3mm screw.

Step 3. Insert the 3mm screw. Inserting a nut is recommended if using a hand saw.

When inserting the screw, test if you are able to remove it by fingers alone. If so,  remove it and add thread locking fluid in-between, and leave the joint to dry for a while.  The nut provides cutting support for the hand saw and is also good for verifying that the threading at the tip of the screw is ok, once cut and filed clean. Probably not needed at all if using a miniature power tool.

Step 4. Cut the screw according to nut. The nut will likely spin, so use your other hand to keep it in place.

Step 5. File the cut clean and remove nut. Half-way there! :)

Step 6. If standoff isn't through-hole by default, make it so. 2.6mm bit once again..

Step 7. ..and add 3mm threading throughout.

Step 8. Lathe the standoff to proper size, making it round in the process. The original hex standoff is slightly under 6mm in diameter (lucky guess: 5.7mm).

Step 9. Cut crossed slots on the other end. This will be used for adjusting the string tension with a Philips screwdriver. Use a miniature power tool (for more precise cuts) if you have one.

Step 10. Test for fit and file the standoff down to around 27mm. All done!

The 28mm hex standoffs I’m using here are just very slightly too long, causing excess turning friction/tightness once installed inside the headpiece. Trimming them down to something between 27.5 – 27.0 mm fixes this. One odd thing is that my caliper says the original standoff is about the same length (28mm), but when installed there still is the difference. Weird, but whatever.

Shortly after fixing this one headpiece mech, I eventually ended up replacing all the Allen / hex screws and standoffs with my DIY Philips type.  The screws are 3mm  (talking about the ones used to clamp the nylon string) so replacing them is equally easy, especially if you have a selection to choose from. I didn’t, so the only black screws I had needed a bit of extra work. Since the screw tips were slightly concave (with sharp edges), each one had to be filed flat to avoid damaging the nylon strings. Despite the edges didn’t look too sharp they did bite well enough into the nylon string once tightened, in turn taking it way too close to the point of snapping up.

Anyway, the replacement was well worth it as it makes more sense to have everything adjustable with a single tool. Even having the two different-sized Allen keys, as in the stock configuration, is pretty stupid.

With the recent sponsorship in mind, oh how I wish a certain well-known hobbyist miniature power tool brand would sponsor me and I could then stop having have to type (the lengthy) “miniature power tool” all the time ;)

*NUDGE* *NUDGE* *WINK* *WINK*

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