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Fixing Broken Buttons/Knob on a microKorg?

 
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christiand5



Joined: 30 Mar 2015
Posts: 3

PostPosted: Mon Mar 30, 2015 11:46 am    Post subject: Fixing Broken Buttons/Knob on a microKorg? Reply with quote

After fiddling around like a caveman for the past four hours with this contraption, I've come to realize why the microKorg I bought off craigslist last night was such a deal. In addition to program button 6 being snapped off (I was blissfully ignorant of how complicated replacing one of those would be), I've come to discover that neither of the octave shift buttons, or the arpeggiator button actually work. The icing on the cake? The program select knob doesn't change the various sound banks either. It's stuck on trance, (which I'm assuming is this machines default on startup) regardless of where I turn the knob. The only reason this didn't immediately stick out while purchasing it, was the thought that the producer I bought it from had it stuck in some sort of edit/midi/write etc. mode.

Pardon my ignorance, I'm totally new to this world. I'm a guitar player, and this was going to be the raddest birthday present ever for my keyboard playing girlfriend. I had four other deals on craigslist fall through, before agreeing to drive five hours roundtrip to pick up one of these from Bakersfield. Long story short, I've been completely and utterly scammed.

BUT I am a quick learner, decent with a soldering iron, and I refuse to give up on this gift. I'm slightly horrified to open this thing up, but is there a way to fix these non-functioning buttons from the inside? I'm assuming I could try cleaning the pot for the program select knob? Has anyone else fixed broken buttons on this thing? I've browsed other posts but haven't found anything as specific as I'd hoped. Thanks everyone, wish me luck as I do my best to explain this mostly-broken/work-in-progress gift tomorrow!

P.S. I'm also new to this whole forum thing, hope I'm not committing some sort of faux pas!
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Spheric El
Platinum Member


Joined: 21 Jul 2014
Posts: 730
Location: Liverpool

PostPosted: Mon Mar 30, 2015 5:45 pm    Post subject: Reply with quote

Shady dealer,nothing worse than flagrant dishonesty.Would you not drive back and bang on his door?I understand if you keep it ,but it sounds like its had some sort of whack to the whole left side as nothing is working.I admire your commitment for DIY (and GF).Do the 1-8 buttons work fine ,and volume?
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christiand5



Joined: 30 Mar 2015
Posts: 3

PostPosted: Tue Mar 31, 2015 3:12 am    Post subject: Reply with quote

It's tough, that drive is nearly five hours for me. Not exactly the nicest part of town either. Maybe I'm unrealistically optimistic, I just don't want to give up on it just yet. Interesting, buttons 1-4, and 7-8 work just fine. 6 was busted in when I bought it, and five doesn't work either. You guys know way more about this machine than I do, but the volume works just fine as well, which leads me to believe that it's not an issue with the entire left side. The buttons click, just to no response. And when I select different programs, some will automatically use the apreggiator, in which case it will light up, I'm just unable to turn it off. Should I begin the process of opening it up and attempting to solve this problem? Have you replaced buttons on the microKorg face before? Thanks again for the response!
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OpAmp
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Joined: 07 Jun 2013
Posts: 792
Location: Brussels, BE

PostPosted: Tue Mar 31, 2015 9:08 pm    Post subject: Reply with quote

Hi,

I might be wrong, but I doubt it is going to be the buttons (alone)...
Google for 'microkorg service manual pdf' and you get a schematic for the internals of the mK.

If you look into it and what strikes me, is that octave up/down, arp, (together with write, bank sel and timbre select) are on the same scan line to the main processor.
It also shows the scanline for the program select rotary knob. Both these scanlines go to IC22 (3 to 8 encoder). So I suspect something in that neighbourhood.

You can open it up, and with some (advanced) measurement tools you may figure out where the root cause is...

Good luck!
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microKORGXL, Kaossilator Pro, monotribe, SQ-1, volca fm, Kross 88 BK
Alesis SR18, Akai Miniak, Fender Strat, Line 6 Spider II 112
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christiand5



Joined: 30 Mar 2015
Posts: 3

PostPosted: Thu Apr 02, 2015 7:22 am    Post subject: Reply with quote

Interesting! Sorry for the delayed response, full time student as well as part time miniKorg tinkerer. I went ahead and took a look at the schematic, and it's a little out of my intellectual reach but nothing that looks impossible to learn. Here's the part where I ask more questions. Correct me if I'm wrong, but these functions do indeed *work,* the buttons just are not toggling the individual functions. When I switch programs (1-8 only, remember the program select rotary knob isn't working either) the arppeggiator and octave selects will light up to what I am assuming is the default for that particular program. Would that still occur if there was something majorly wrong on the circuit board?

Another question. The write, bank sel, and timbre select are all fully functional. Does that negate the scan line theory? Everything I've looked into has seemed to point to a faulty contact underneath the buttons, and a dirty pot underneath the rotary knob, which I believe I could fix with an afternoon and a cold one. But if that doesn't do it, I believe you're right with looking into the circuit board.

Last question. I noticed in the schematic included instructions for a test mode. Is this not the end all solution for troubleshooting? I haven't read anything about this before, and I'm getting ready for a massive road trip commencing tomorrow, so not sure I'll be able to test this anytime soon, but I was just wondering if that test mode has helped any of you in the past.

Seriously, thanks for all the input guys! Cheers.
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OpAmp
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Joined: 07 Jun 2013
Posts: 792
Location: Brussels, BE

PostPosted: Thu Apr 02, 2015 7:25 pm    Post subject: Reply with quote

Hi,

Q1: The functions would still work, as long as the main cpu and dsp are booting and so on. The problem is that the buttons are pushbuttons. Suppose something is broken in the 3-to-8 decoder (IC22), then when the main cpu scans the failing buttons, it simply can not detect that they are pushed or not. And thus they can not toggle the function. Failing to scan the state of the button is independent of the function itself and whether it is on or off in a certain bank.

Q2: if these buttons are fully functional, then you can forget my scan line theory, because those would fail as well then. Maybe you're right and it is just a matter of cleaning the contacts. You'll have to open it anyway to figure it out...

Q3: not sure what you can do with the test mode on the mK. I would not call it the end, but rather a starting point for troubleshooting. Very Happy It is typically a diagnostic tool to check few things (sanity check) before the board is packed and prepared for shipment to shops.

Enjoy the trip and keep us posted on the fixing of the mK.

Bye
_________________
microKORGXL, Kaossilator Pro, monotribe, SQ-1, volca fm, Kross 88 BK
Alesis SR18, Akai Miniak, Fender Strat, Line 6 Spider II 112
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LFOperation



Joined: 29 Mar 2017
Posts: 1

PostPosted: Wed Mar 29, 2017 2:32 am    Post subject: Some buttons on the Microkorg not working after fixing keys Reply with quote

I had to open my microkorg once to fix a key that had been dislocated a little and I put it back together as well as I can. It works, but recently, three of the patch select buttons aren't lighting up or selecting.

Is this an issue of the board not being screwed down enough or do I have to clean it? I have the service manuals, but I do not know which equipment to use.
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