The following plans describe a method of adding
MIDI capability to the Korg Mini-Korg analog synthesizer with the Synhouse
MIDIJACK II: Hertz
so good! The Mini-Korg is especially well suited for this modification
due to the tiny size of the MIDIJACK II circuit board and the fact that
it is the first analog MIDI retrofit ever made that costs less than the
instrument itself! Some drilling is required. There is plenty
of space on the Mini-Korg to mount the MIDIJACK with the provided hardware.
You may be able to do this yourself if you have experience with electronic
repair and the soldering of wires and circuit boards. If
not, it is recommended that you send the instrument to Synhouse L.A.
for a quick, low-cost Factory
Installation. The particular installation on which this document
is based was not done by Synhouse, but rather a
very helpful Analog User, so neither Synhouse nor the Analog
User who provided this is responsible for the accuracy of this infomation,
nor any damage to your instrument or MIDIJACK II resulting from the use
of it, misuse of it, or inability to use it. Those who
choose to read it and use it do so at their own risk. Synhouse does
not have any direct knowledge about this particular installation,
but the author may be willing to answer questions if they are asked nicely.
It is best to download these notes and photos and print them out on paper
to look at while working on the instrument and make notes and check off
the steps as you go. As with any project, you should completely
read and understand each step of the instructions before starting.
All repairs and modifications made to your instruments will be done at
your own risk and Synhouse Multimedia Corporation assumes no liability
for personal injury caused or damage to equipment or loss of use caused
directly or indirectly by the use of these plans. If in doubt,
don't do it!
MIDIJACK II installation in Korg Mini-Korg
700 or 700s.
Please note that I installed my MIDIJACK II
with NO bypass wires. I did this simply because the Mini-Korg keyboards
I have played have corrosion on the contact wires (in a difficult-to-clean
place) which causes some wrong notes when playing grace notes or very lightly.
I felt it best to play via MIDI only.
Locate oscillator board, shown in pic
korg001.jpg as the lighter colored board in the middle, labeled SB-019:
Solder MIDIJACK #1 black wire to contact 40
GND. Do not disconnect existing black wire.
Solder MIDIJACK #2 red wire to contact 37
+VCC. Do not disconnect existing red wire.
Desolder the gray wire from contact point
38, solder MIDIJACK #6 green wire to pin 38. Tape and secure
Locate the 3.9K resistor shown in pic korg004.jpg
with the MIDIJACK #4 white wire attached:
The board has a silkscreened triangle under
the resistor. Solder the MIDIJACK #4 white wire on the upper lead,
the side on the top of the triangle.
Locate the 4.7K resistor just to the right
of the MIDIJACK #4 white wire (NOT the 47K which is nearby). It will
have an upside-down triangle on the board. Cut the lead in half with
Desolder the brown wire from the keyboard
assembly, tape and secure it.
Refer to pic korg005.jpg for a look at how
I mounted the MIDI input DIN jack on the rear of the Mini-Korg:
Refer to pic korg006.jpg for a look at how
I mounted the MIDIJACK circuit board on the rear case top:
Refer to pic korg007.jpg for a look at how
the completed MIDI control panel looks on the Mini-Korg:
I would recommend saving some room on the
cover in case you want to add some other mods to the synth - this black
cover is an ideal place to add hardware.
Button up the rest of the installation but
leave the cover off. Power up and check it. Once you have MIDI
In, play in unison with another synth. Tune C4 using the external
tuner slider. If you are out of range, use the internal 5K
pot on the oscillator board (2nd from the right) to bring it in tune.
Now play C2, C1 and C5 - if they are
not in tune, then locate the single pot on the voltage board (leftmost).
Connect a VMM between the orange wires and chassis ground. Play C4
and check the voltage. It should be somewhere around 20V, but
adjust between that pot and the 5K osc board pot to bring it in tune,
linearly across the keyboard. I had to drop my 20.7 volts to 20.4
volts after the MIDIJACK II installation and keyboard removal.