Korg M1(r)/M3R -1988    Weight = 29.7 Lbs. Number mfg.= 250,000 MRP=$2166


User Manual: VSE or M3R pdf's
Reset Proceedures: Hold "INT" while powering up for ROM version, or add "CARD" and "COMBI" to reset
Operating System code:
MIDI or other control protocol:
Software related Links:
Patches or knob settings: VSE
Circuit Overview: below
Scematics/Service Manual: fdisk service manual
Common Service Issues/Tips: below
Parts Sources: Keys knobs semiconductors misc
Uncommon chips/modules used: Many. Burr/Brown PCM54HP DAC
Modifications:
General Info Links: Vintage Synth Explorer



Circuit Overview:
     A 16 voice digital ROM Wavetable synth. A "Standard" for gigging musicians for so many years they are still in higher demand than much better sounding/more versatile keyboards. For it's day a great one though. The M1r is the rack version and the M3r has the same sound engine I understand but is limited to single oscillator but can be stacked in combi and naturally patches are NOT compatible with M1 which has oscillators stackable within a patch.

Service Tips:
     I've seen failures on cpu board that cause it not to boot. Best to find a beat up unit to swap boards with. Korg wanted way more than the units go for in nice condition and they were on backorder last I checked the price/availability on *that* board... The buttons crack often and a careful use of a solder tip can melt plastic back together enough to then overlay goop adhesive quickly in select areas to add strenght and make these good as new in a pinch! I think Korg still sells them maybe too. The switches normally can be cleaned with contact cleaning and a lot of tapping on the switch. Keep checking until they get to a tenth ohm resistance when on.

I also just worked on an M1R that had some bad solder in the midi and a flagrant oxidized pair of contacts on a coil in the output filter of the 12V supply. Cleaned that up and it worked swell.


Parts:
I have some remaining parts from a scrap out. Analog board, jack board, keys etc.Contact