Korg Forums

reinardvanloo · Joined: 15 Mar 2015 Posts: 5 Location: Vienna, Austria

Hi all,

Just got me a second hand M3m for a good price, but one of the 8 pads (number 4) is not working. The other ones work fine.

I did run the pad-calibration routine - no luck.

I thought that it might require some carbon contacts cleaning inside, so opened it up (trust me, I knew what I was doing; resurrecting old synths from the dead for years now) and drilled down to the pad PCB, to find that these pads do not use carbon-contacts.. cannot figure out how they work and/or could be repaired... Hal-effect? something else?

SOO... long story short following questions:
1) does anyone have the schematics of the PAD contact strip PCB of the M3m?
2) If not, anyone had a similar issue (calibration did not solve it) and found a solution?
3) if all else fails, does anyone have a working PAD-PCB lying around I could buy?

regards,

---Reinard

reinardvanloo · Joined: 15 Mar 2015 Posts: 5 Location: Vienna, Austria

Sooo.. I think I found it:

First of all, after some searching found the M3 service manual *with* schematics! You can download it from http://elektrotanya.com/korg_m3_sm.rar/download.html

The pads work using magnets and Hall-Effect sensors (the infamous, well known, world famous (not...) HG-106C-FT.) Actually, brilliant: not contacts that can wear out! Try moving a strong manget over the pads, they should trigger...

First, tested the Pads using the built-in test mode (press enter+5 at start up). Pad 4 has very low readout values.

Opened it up, and after measuring the voltage generated by each pad when pressed (easy: Measure voltage from pin 2 on WD4) Pad4 is the odd one out maxing out at something like 0.4V, where the others have as min 0.6V or something... This also leads me to think that the surrounding circuitry is ok, just that the Hall sensor is not ok. (also measured the voltage at the HAL sensor side of R13: same as on the other pads, so the temperature compensation circuitry I am assuming is not broken... will test this later as well)

So the thing to do: get an HG106C and replace the one on the PCB and see if it works again...

keep you posted...

---Reinard