Korg Forums

[aphelionz]

Hi there, I recently picked up a used "as-is" Microkorg and I love it! However, the arp toggle button doesn't seem to function. I'd love some help troubleshooting it if help is available.

The status currently is that every other knob and button works except for the arp on/off button, and even the arpeggiator itself works. For instance, I can switch to a patch that utilizes the arpeggiator and it works fine (even the 8 sequence buttons work). The arp status LED also works fine - it's just the toggle functionality itself that doesn't seem to work.

Here's what I've tried so far:
1. Cleaning the device inside and out
2. Replacing the dpdt switch with one from Syntaur
3. Checking all the traces on the PCB and as many components as I could visually inspect - nothing obvious jumped out at me.

I'm happy to keep using the device because I can hook an external sequencer up to it to help augment the broken functionality, but I'd love any pointers or things to try from here.

Thank you!

[OpAmp]

Hi,

Did you also look at the Service Manual? You can google it.

It contains the schematics. The ARP button is taken up in a scan matrix. Given that all other buttons and knobs works it means that the column and row lines for the ARP button should be fine.
Left then is the switch itself (which you replaced) or the diode nearby. Could you check the diode? Maybe it is broken.


Good luck!
_________________
microKORGXL, Kaossilator Pro, monotribe, SQ-1, volca fm, Kross 88 BK
Alesis SR18, Akai Miniak, Fender Strat, Line 6 Spider II 112, Zoom MS-50G

[aphelionz]

Thanks for your reply. I downloaded the service manual.

Looks like I need to get a multimeter with a diode test function now! I did test the traces between the dpdt switch, the diode in question (D16) and the next D19 and it all seem sto work but I can't tell if the diode itself is functioning.

After staring at the schematic for a while I can't see anything else it could be and I ...think... based on my extremely limited knowledge of EE that a busted diode could be causing this issue of the switch not toggling the arp on and off.

I will report back.

[OpAmp]

Hi,

Indeed if the diode is broken and is always open, pushing the ARP button will have no effect.
A simple multimeter with the option to check continuity will do the trick.
In one direction, current should flow, in the other direction, current will be blocked.

Curious about the outcome...
_________________
microKORGXL, Kaossilator Pro, monotribe, SQ-1, volca fm, Kross 88 BK
Alesis SR18, Akai Miniak, Fender Strat, Line 6 Spider II 112, Zoom MS-50G

[aphelionz]

Well, I got a multimeter with a diode test function and... for better or worse D16 seems to be functioning properly

What now?

[aphelionz]

Ok, staring at this some more and trying to figure out more about what's going on (or not going on)



Am I correct in reading this schematic that one of the poles of SW17 should connect to one of the poles of SW4, the arpeggiator switch?

Because putting my meter in continuity mode does NOT beep when I touch those two points... could that be the issue?

[OpAmp]

Hi,

Yep. When doing continuity check, there should be a path from one of the poles of SW17 to SW4.
A new switch SW4 , a working D16 and all buttons and selectors working, then it can only be a trace or soldering point not ok.
_________________
microKORGXL, Kaossilator Pro, monotribe, SQ-1, volca fm, Kross 88 BK
Alesis SR18, Akai Miniak, Fender Strat, Line 6 Spider II 112, Zoom MS-50G

[aphelionz]

That was it! The trace was bad. I wired a jumper cable in and that fixed the arp toggle. The unit is still pretty beat up cosmetically but it's fully functional now

Thank you OpAmp for all your help.

[OpAmp]

Hi,

Very well done!
Enjoy your excellent debugging and repair work. Time for some music!

Hqve fun.
_________________
microKORGXL, Kaossilator Pro, monotribe, SQ-1, volca fm, Kross 88 BK
Alesis SR18, Akai Miniak, Fender Strat, Line 6 Spider II 112, Zoom MS-50G