Below is a video in which I discuss a pitch bend problem in a Korg Synth MS-10. The main thing is how to look at the schematic and determine what voltages should be present in the circuit.
Where the fun begins is when you don’t have the voltage present and you have to figure out why.
The + and – 15 volts D.C. are the output of a typical analog power supply in equipment from this era. This goes to the pitch bend pot that can affect the voltage.
As you turn the pot it gives the desired output voltage that the synth player is looking for to drive other modules on the synth. The customer’s problem is that is wasn’t working at all. The problem ended up being an oxidation buildup on the molex connector that connects the pot pitch bend assembly to the main board where the power supply components reside.
So it was a simple repair but in the video you can see how I came to this determination and also by studying the schematic.
9 thoughts on “Korg Synth MS-10 Pitch Bend Repair”
I’m digging the video…my MS-10 is now famous!
spudzzzz in Ethridge
Hi Gary – I’m just curious about how you remedied the oxidation buildup in the molex connector? I fear my own MS-10 may have the same problem. I have applied some de-oxit to the male end of the connection (mounted on the motherboard) but I’m not sure how to get the inside of the molex connector clean.
Sometimes it’s easier just to find which one of the traces in the connector is not connecting. (Checking with an ohm meter for continuity) And just hard wire a jumper wire in place between the circuit boards or preferably just jump around the molex connector. That way it’s hard wired and you don’t have to worry about the equipment marching back in for the same problem.
Of course if you can replace the connector that works or bend the pins out enough to have tension between the teeth and the mounting post and it makes a tight connection.
That Funk Out by Peavey that I talk about is good for this also.
gary….don’y know if you’ll get this…..i am living in mexico and am experiencing problems finding a repair shop here to fix my lazy key with my yamaha p-80 electronic piano….you were a tech guy?……wondering before i open my piano up…..if you had any idea on the degree of difficulty……the key is the c above middle c….does’nt react well…..falls midway….i can get parts shipped here……thanks……jim
I believe that one can be a bit of a bear, I’ll dig around and see what I can come up with. Usually when it returns half way, the key is broken in the back where it pivots, kinda the weak point. You might have the tension spring loose for the return but usually that doesn’t happen.
Hi, I have a Kurzweil KME-61 with problems in the Pitch Bend and Modulation wheels, the problem not is mechanics, it’s digital. I cannot find the plane of the circuit and don’t know how fix it. Help me, please! Thanks!!!
If you’re sure it’s not the mechanics the only thing I can think of off the top of my head is reset the unit. Put it back to Factory Presets in the global area I believe. MAKE SURE YOU BACK UP FIRST!
Possibly some erroneous data is affecting pitch and mod data somewhere in the unit.
Hope that helps…
Hi Gary! I am looking for a nel potentiometer for my Korg MS20 Pitch Bend Wheel ..I have a pic of it..it is a 10K Ohmn but with 4 pins..seems pretty hard to find it here in Italy… do you have suggestions? any help would be very appreciated.
hmmm that’s a tough one. Talk to places like Mojotone, (they may know of someone) digi-key – mouser – even scour eBay. Also put up posts on analog synth sites, there’s some very knowledgeable people that hang out on some of them. Since it’s an older pot, if nothing else pry it open (if totally messed up) see if it’s the wiper and not the graphite track. If it’s the wiper you may be able to switch it out. Also that Peavey Funk Out spray I’ve seen bring all kinds of pots back from the dead. I’ll look through my parts and post if I find anything but a 4 legged is a bit rare in an older pot.