Grant Muller

Casio MG-510 Midi Guitar

Back when I documented the repair of the Casio PG-380 MIDI Guitar, I had no idea that this post was going to dominate the traffic patterns to my little home on the web. Fully 1/3 of all visitors to this site come to that post, asking questions, posting comments, and requesting repairs. One request I’ve gotten over and over is a repair on the Casio MG-510.

The Casio MG-510 is like the little brother of the Casio PG-380. The base functionality is similar, but the 510 lacks some of the extra features that the PG-380 offers. The 510 has no space for an expansion slot, and no internal synthesizer, which for most software synth users is just fine. The biggest differences you’ll notice between the 380 and the 510 are hammer on sensing and the ability to perform pitch bends. The 510 is strictly chromatic; when you bend it assumes the same pitch until you bend far enough to change notes, in which case a note off and note on message are sent and interpreted. The 380 will perform a pitch bend at even the slightest pull of the string.

The 510 and 380 share one major flaw though: the electrolytic capacitors used for the pitch envelopes. These heinous little surface mount caps tend to leak over the years, especially on the 510, leading to corrosion and in most cases total failure of the MIDI capabilities in the guitar.

I finally got around to repairing one of these guitars, and the process is so similar to the PG-380 that it would be a shame not to document it. If you’re new to this you should probably refer to the post on the PG-380 before getting started.

You will need:

  • 6 x 1 uF non-polarized electrolytic capacitors
  • 4 x 10 uF polarized electrolytic capacitors
  • 1 x 22 uF polarized electrolytic capacitor
  • 1 x 4.7 uF polarized electrolytic capacitor
  • 1 x 33 uF polarized electrolytic capacitors
  • Anything you need to unsolder old capacitors and solder on new ones

First, crack open the back and take a look at the boards:

(1 of 5)

You’ll see two double-stacked and plugged into three header cables.

Take both boards out (unlike the PG-380 you have to operate on both):

(2 of 5)


Take a look at the capacitors on both boards below:

(3 of 5)

Top of PCB 1 – C9, C18, C33: 1uF non-polarized electrolytic


(4 of 5)

Bottom of PCB 1 C42, C52, C63: 1uF non-polarized electrolytic


(5 of 5)

Top of PCB 2

  • C4, C22, C29, C12: 10 uF polarized electrolytic
  • C30: 22 uF polarized electrolytic
  • C31: 4.7 uF polarized electrolytic
  • C48: 33 uF polarized electrolytic

Basically, for both boards, replace the capacitors with the caps above using capacitors of identical value. It shouldn’t matter if you use polarized caps for the entire repair, since the frequencies are not high enough to affect response times, but use non-polarized where needed above if possible.

You will find that you have 2 "extra" caps (seems like 2 for each string plus 2). I know that one capacitor is used for CPU reset (C30), but I’m not entirely sure what the last one is for. I replaced it anyway.

Some notes:

  • The traces on the top board are very small. You might find yourself pulling them while unsoldering the old caps. Not to worry, there are plenty of places to solder the new caps.
  • Corrosion makes for crappy contacts. If you find that your caps have corroded, particularly on the lower board, you will need to sand the corrosion down with steel wool or other light abrasive until you can expose some copper to solder to. On the guitar I repaired the corrosion was severe, and I spent a lot of time scraping out leaky capacitor guts.

That’s really all there is to it. Plug the boards back into their headers, screw them back into the guitar, and adjust the trim pots as needed to calibrate the guitar again.



  1. Dear Grant,

    I was told by a trusted repair tech that the problem on my MG-510 is the midi pickup not the capacitors. My b string does not fire. What do you think and how do I determine which it is?


    1. Did you get the G string pickup replaced?  My D-String is not working.  The link below (ubertar) does not have replacement.  He asked me to send the pickup & he will re-coil.  Will the capacitor change might fix the D-String issue? Should i try to change the capacitors before changing the individual pickup?

  2. i fixed the all the problems about g string and the capacitors.the midi device works almost`s very hard to set the corect values for strings sensitivities an pickup height.a few notes  apear to repeat sometimes but i understand is an old midi device and this is ok for me.

  3. Hi all, I looked at the schematics on yahoo groups.  C48, L1, C12 -> IC 5, stabilizer -> C30  are all for power supply. C31 for reset signal.  Mine is tracks notes great, only completely at random (!) it sends CC all notes off signal (I hope it is a reset triggered) Do you have any ideas why this may happen? 

    thanks for posting!

    1. I’m not really sure Erik. I haven’t encountered one with this particular problem. How frequently does it do that? It doesn’t cost much to replace C31, and it wouldn’t hurt anything. It’d be worth a try.

      1. Symptoms are typical,  fails first 20 minutes, then warms-up and back to normal.  Also if MIDI octave is down, the octave change rapidly sometimes – sounds like a funny tremolo.  When failing  it stops sending MIDI sense signal, which cause the synth to generate  CC all notes off signal for all strings. 

  4. i replaced my caps in my pg380 but now in regular mode it freaks out the the pitch bend when the guitar is connected to mbox and used as a trigger … any ideas (it never did that before the cap replacement

  5. You are wring when you say the MG-510 does not track pitch bends.  It does.  If the switch is set to “chromatic”, it behaves as you describe but if set to normal it tracks pitch bends just the same as th PG-380.  It has no problems with hammer-ons either.

  6. Hi Grant, I found your really helpful blog, but I need a guitar tech in London. Last night I stupidly plugged my J-station mains adaptor (9V 2.1A, instead of the Casio 9V 8VA adaptor) into my Casio MG510 without realising until I smelled hot electrical circuits.  The power light still illuminates, but no midi out, no tuner function so I must have fried something inside it.  Casio tell me they no longer support or repair this guitar, so I am stuck.   I have found an interesting monophonic Analogue – Midi unit from Sonuus, which gives me some hope, but is a repair possible?

    1. I doubt you fried the caps for the envelope follower, its more likely you burnt out the voltage regulator a little earlier in the circuit, or the caps that protect the power supply. I could look into it but its not the same repair, its more likely you killed something in the voltage regulation area of the circuit. 

  7. Hi – do you know if it is possible to use the casio as midi controller without a keyborad but direct to midi plugin instruments on the computer?

  8. Hello folks!! i have a mg 510 guitar and I have some issues:the midi is not working properly:sometimes the note is not heraring and sometimes it hears repeated or by itself(without picking a string) I have the service manual for casio mg510(some people around here ask me for it and i gaved it by email) somebody before me has changed those electrolitic condensators with new one but seems not to be the same specifications(the new ones are 100v 1uf) a friend of mind (he nows about electronics)told me that they are ok.he also measured some parts and did some tests (as sad in service manual) and the leds says that the device is ok.

    any opinion or advice about that issue???

    ps:Grant maybe you can advice me (for my electronist friend)what else should I do thank`s and escuse my bad english!

  9. as aan adagio :i sad that all capacitors are 100v1uf they are not.i just look at the top baord and i saw that is also one capacitor 33 uf 100v

    could be the voltage parameter a problem??i mean 100 v on the new ones?

  10. I am seriously considering purchasing one of these guitars.

    I am assuming you have to plug both the regular 1/4 jack and midi cable into an amp to play live. I have a Hughes & Kettner Tubemeister. It only has one input so what could be used to plug both of the cables into the amp. Also what could be used to adapt this to my Line 6 wireless setup.

    Any help is greatly appreciated.

    1. You really need 2 amps. Think one for the guitar, and one for the MIDI. Since My MIDI went into a Korg tone generator (analog/digital; no keys), that output went into a keyboard amp (200 watts, 15″ w/ horn). For awhile I had stereo guitar and stereo keyboards that sounded great for me on stage, but nobody else could hear the stereo effect.

      Anybody know of a repair person that would upgrade my Casio 500. Still works, just want it to work as best as possible. thx

  11. when purchasing these caps is there any more info i need other than them being 1 uf non-polarized electrolytic caps??

    thank you

  12. Can any tell me the why the third string G Is not playing on my mg 510 casio midi guitar Thank you for your time. Steve

  13. I know that the MG-510 needs a center-negative AC adapter outputting 9V DC but does anyone know how many amps the guitar draws when using midi? I need to find a power adapter.

    Thank you

  14. On my boards, I see that C34 and C48 are missing, as on yours. When I opened the back of my MG-510, I found one cap alone, one of the two 33 uF. My question, C34 or C48 ? Thanks Eric

  15. Could you,please,email me basic wiring 5way switch,magnets and switch of Casio MG510,because some art mastyer with solderin iron ruined whole conception

  16. Any ideas as to why, one string (A string) would stop working all of a sudden? Everything else is fine but the A sting sends no signal out to the synth, nor does the onboard tuner led’s react when plucking the string. This is on a MG-510

  17. Hey Grant, I found your blog entry on this guitar, and it happens that I have one which needs to be repaired. Can you do that? 😉 I talked to a lot of service/repair guys and they all said they don’t want to do it.

  18. I have the 510 and love it, well-when it works. My problem is the guitar jumps from violin, organ, or sax to piano. I’ve gone thru 3 midi cables thinking that could be the problem. I’m not good at finesse soldering so I’m afraid to tackle replacing the capacitors. Does this sound like a capacitor problem? Love this forum by the way, thank you

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