Casio DG-20 guitar teardown
I bought a Casio DG-20 digital Midi guitar a few years ago thinking that it would be a cheap way to input Midi data into my sequencer using guitar fingering. I was partially right, but the feel of the instrument is not quite the same as a real guitar. The pressure-sensitive fingerboard is certainly unique, as I don’t know of any other controller that detects input in quite the same way.
My particular instrument was purchased on eBay from a person whom I think really didn’t know much about the guitar or its history. When I got it I noticed that the neck was bowed and there were several dead spots on the fretboard. All in all, it was in working order though, so given the rarity of these things I wasn’t too devastated.
I have made one previous attempt at tearing the guitar down in order to see if I can fix it. I didn’t have time to completely figure out how to get the neck off of the guitar in order to see what was wrong with it. Here I will document the second teardown attempt, which has been successful so far.
Step 1 – Remove the back of the guitar
In order to get started, we need to remove the back of the guitar. There are components attached to both halves of the guitar, so it may be more accurate to say that we are just opening the thing up, or splitting the halves open. Remove all of the screws in the back except for the screw that holds the strap button on. Note that the metal back plate that attaches the heel of the neck must be removed in order to open the guitar up.
Step 2 – Remove the neck
Once we have the guitar open, in order to remove the neck we need to remove the two screws that are still holding the neck on that are located in the area between the heel posts that stick up toward the back of the instrument. There are also three nuts that must be removed. The nuts are located just to the right of the heel of the neck in the picture above. These nuts hold the metal stay that keeps the rubber contacts of the fretboard in contact with the ‘common’ wiring. There is one extra nut that attaches a ground connection eyelet. Once the last nuts and screws have been removed, the neck will lift clear of the body easily. If there is any resistance double check that the screws and nuts have all been removed.
Step 3 – Remove the fingerboard
The fingerboard is held on by double-sided adhesive tape and two small allen bolts near the nut. First, remove the allen bolts using a 1.5mm allen wrench. The bolts can be exposed by gently pulling back the rubber fingerboard material near the nut of the guitar as shown in the photograph above. Once the allen bolts have been removed, carefully pry the fingerboard circuit board up from the neck of the guitar, starting at the heel of the neck and working slowly up toward the nut. Since the end of the board is exposed near the heel, you can pull up gently on the end of the board to get started, and then insert a thin screwdriver several inches down the neck to start prying up the fingerboard. Continue along the length of the fingerboard until the whole board is free of the neck.
The screws that were supposed to be holding the metal truss rod in place were rattling around inside of the neck. Also there was some damage to the screw holes where the screws were supposed to go. I’m not sure if the instrument was dropped, causing the screws to shear off, or if someone had already opened the neck up to try to fix it before. The metal bar is quite heavy, and seems to serve a dual purpose: to keep the neck straight and to balance the weight of the guitar.
Now that the fingerboard has been removed, the hard stuff is over. The rubber contact material will just pull off of the contact circuit board, as the only thing holding it on now is a small grove in the rubber material into which the edge of the circuit board fits. In the next picture we can see the contact surface of the circuit board and the contact surface of the underside of the rubber fingerboard.
Notes on the fingerboard design and operation
The integrated circuits that can be seen on the reverse side of the fingerboard are actually diode arrays that are intended to prevent ‘ghosting’ of finger presses. Since the operation of the guitar requires that multiple finger presses be accurately read by the guitar logic, diodes must be installed to prevent false keypresses from being registered. Note that this is not the same as debouncing. The wiring layout of the fretboard is a simple matrix, which is probably scanned by the input controller logic to determine which frets are being fingered. There is a really good explanation of key scanning and ghosting here. The datasheet for the diode arrays can be found here.
Fixing the dead frets
The resistive contact technology used in this guitar is the same that is used in most synth-action keyboards. Therefore, I am pretty confident that this controller can be fixed by using conductive paint (found in automotive windshield defroster repair kits) on the rubber contact strips of the fretboard. I have repaired my Edirol PCR-30 keyboard in this way. However, there also appears to be some damage to the ribbon cable wiring that is used to connect the fretboard to the rest of the guitar circuits. The ribbon cable was pinched severely in the heel of the guitar when it was reassembled by a previous owner. I’ll detail the repairs in a follow-up post. In the meantime I’ll share a few close-up detail shots that I took of the fretboard assembly.
Close-up of the rubber fret contacts
Close up of the circuit board contacts. Note that the fret itself would fall in the space between the contacts.
Detail of the Sanyo diode IC used
Thanks for the information! I personally really appreciate your writing. This is a great website. I will make sure that I stop back again!.
Beginning Guitar Lessons
March 16, 2010 at 11:09 am
Hi my name is Josef and live in Malta(a tiny island in the Mediterranean sea South of Italy). I have one of these guitars and I need a replacement String Retainer (at the headstock). Can you help me find one? Can you sell me one?
Thanks
Josef
josef camilleri
May 5, 2010 at 6:01 pm
Hullo,
I have just got one of this things from ebay. It seems in very good condition but the neck is bowed making the action uncomfortable. Is there any way of rectifying this ?
Many thanks
antonio
July 1, 2010 at 6:51 am
@antonio – In the pictures of the neck you can see the metal counterweight that balances the guitar and also keeps the neck straight. If yours is rattling around inside like mine was, it probably was dropped and the weight broke loose inside of the neck. The only way to fix this would be to repair the screw holes in the plastic with epoxy or filler and re-thread the screws. I’ve been planning on doing this with mine, but I have not had the time. Good luck.
newcome
July 2, 2010 at 2:05 pm
Newcome,
many thanks for your reply. In the meantime I have had a go with the help of your pictures and I seem to have rectified the problem ! I unscrewed the metal strap ( in fact three straps loosely glued together ) and roughly bent it in the opposite direction of the bow of the neck. When I screwed the strap back and reassemble everything, the neck was a lot better, practically straight with a very good action. Rather coarse method, not really finely adjustable, but did the trick for now. Having the pics available and knowing somebody had opened this thing up without destroying it was great help.
Regards
Antonio
antonio
July 7, 2010 at 7:05 am
I have a DG10 that I am trying to MIDI. Any photos of the main board would be really useful as I am convinced it is almost identical to the DG20.
The schematics are at http://www.mediafire.com/?wnjmjnzg4dm
Carl
Carl JR
August 3, 2010 at 1:37 pm
I just bought a used DG 20 that seams to show the same dead spots problem on the fretboard. So I found this post very useful: I was able to open the fretboard and I’ll try to fix it.
Simply “grazie mille”!
Giovanni
August 22, 2010 at 11:19 am
wow that’s some serious machinery
casio sure knows how to do things
Casio
Muzyka
December 3, 2010 at 8:19 am
Hi, I have a DG20 and I need to find a replacement string retainer in the headstock like Josef. Do you know anywhere we can source spares for these? Do you have a spare? ANy help would be a great help?
Duncan
December 13, 2010 at 1:42 am
I have 2 DG-1s, 2 DG-10s, and 2 DG-20s. All are fully functional but one of my DG-20s has a strange problem. The rubber fretboard is bowed up – even though the neck is straight. you can push the fretboard down into the neck, but it will pop back up when you release pressure. This of course makes the action suck, but there are no dead spots on the fretboard. Playable, but not fun to play. Any ideas on how to make the fretboard stay flush without disassembling the guitar?
Wes Regian
January 28, 2011 at 12:41 pm
@Wes the fretboard is held in place with thin double-sided adhesive tape. If it is the board that is coming up you could put some more adhesive tape down. If it is the rubber part, perhaps you could stretch the rubber a bit by putting some tape along the sides of the rubber and wrapping it back behind. I think you should be able to do this without taking the neck completely off, but you will have to take the back off of the guitar in order to get the pressure plate that sits at the heel off. The pressure plate holds the fretboard in place at the heel. The nut fasteners can be removed easily as shown in step 3. Good luck.
newcome
January 28, 2011 at 1:12 pm
OK I’ll give it a try. Probably will be able to get to it this weekend. Sincere thanks for the guidance, and I’ll let you know how it goes.
Wes Regian
January 28, 2011 at 3:50 pm
looks like there’s a problem when I tried ti download service manual of casio dg20 at :http://www.mediafire.com/?wnjmjnzg4dm, it says it has been deleted.
jojo
September 15, 2011 at 7:55 am
Recently bought a DG-20 on e-bay that will not turn on. I’ve tried it both with AC adapter and with batteries. No power getting through. The guitar seems in great condition otherwise. I also own a DG-10 that still functions but is kind beat up. What I really want is the MIDI out on the DG-20. Do you have any recommendations on swapping out parts to get the DG-20 to work? Getting the schematics might help a lot. Thanks.
Matt Hamblin
September 20, 2011 at 12:19 pm
Try here for the answer to the power problem: http://templarseries.atspace.com/dg.html#Fix
joe
October 7, 2011 at 11:24 am
I have two of these babies (used to have three), but both of them are somehow faulty. The other one doesn’t power up at all. The previous owner told me that he had probably used a PSU that was too “powerful” for it and it has “burned up” inside.
The other one has one of the bolts broken in the string retainer-section. So it’s only a five-stringer at the moment. I would like to make one working guitar from these two, but can’t get the bolts loose from the burned-up guitar. It loosens up to a certain point, but after that it gets stuck and just spins around without coming completely loose. Any expert suggestions?
Tomi Tuominen
October 25, 2011 at 10:34 pm
Tomi, I think you can take the headstock cover off if you remove the fingerboard. As you can see from my teardown, it is a little tricky since it is held on by some aggressive adhesive tape. I think if you unscrew all of the hex bolts that hold the strings on you will be able to remove the headstock cover and see what the problem is. I don’t have my guitar in front of me, so I’ll try to comment when I look more closely.
newcome
October 26, 2011 at 2:34 am
Thanks a million Dan!
I’ll see what I can do. It would be just perfect to get at least one of my guitars in perfect working order.
Tomi Tuominen
October 27, 2011 at 4:13 am
Anyone still got the DG20 service manual? It was deleted from mediafire site. Maybe you could upload it to some other free online service, like say http://shareflare.net
Thanks
vldmrrr
November 1, 2011 at 12:56 pm
I have DG-10 service and user, as well as DG-20 service and user manuals. Dan I can email them to you if you like.
Wes Regian
November 1, 2011 at 1:27 pm
Hi vldmrrr, I put the service manual up here for now:
http://dnuke.com/files/DG10-DG20-service-manual.pdf
It is really a good resource for these guitars, it’s a shame Casio doesn’t provide it anymore.
newcome
November 1, 2011 at 1:42 pm
Also, @Wes – if you have a better version of what I uploaded, or something I don’t have, I’d like it if you’d email them to me and I will post them also. There seems to be a lack of anything out there right now on the DG10 and DG20. I’m glad to have found the service manual when I did.
newcome
November 1, 2011 at 1:45 pm
We have the same DG10/20 service manual. I also have the DG-10 Players Manual, and the DG-20 Players manual. These are essentially user’s manuals. Both PDF.
Wes Regian
November 1, 2011 at 1:56 pm
Thank you, Dan!!!
It is really great resource. I’ve looked into getting it some dedicated permanent place on the web. I know some yahoo groups for synths have service manuals in their files section. I tried to create one for casio dg, but for some reason I was not able to upload there – maybe the file is too big or it takes time before upload would work. Will try later, Hopefully it would be easy to find it that way
Thanks
vldmrrr
November 1, 2011 at 6:31 pm
Just assembled one fully working DG-20 out of the two dysfunctional ones I had previously. Thanks for all the advice. If anybody here is in need of spare parts for their DG-guitars. I’m cannibalising the broken guitar for parts. The battery compartment cover is already sold.
Tomi Tuominen
November 8, 2011 at 11:52 am
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December 28, 2011 at 7:04 am
this is awesome! thank you! i dont have any dead frets really. just a few frets that cant decide wether or not to play the note its assigned, or its neighbor a half step up.
Lucas
February 2, 2012 at 1:33 am