sample and hold circuit used by the Minimoog has always been unstable
and caused many players problems in many situations. Many users have
to control the Minimoog by external CV and S-trigger, only to find
that the instrument constantly goes out of tune. This is due to the
leakage of the sample and hold circuit in the Minimoog. The Original
MIDIJACK and this installation method engineered for it incorporate a
bypass modification to solve this problem. There is no need to
hit a key before each take to charge up the sample and hold again,
because the MIDIJACK properly bypasses the keyboard the way that any
I/O signals are easy to find and connect to the MIDIJACK, and all
connections are made on a single board. The entire MIDI conversion
job can be done easily in one hour or less. This modification reroutes
the local keyboard signals through the computer-controlled analog
matrix of the MIDIJACK by extracting the signal and inserting the users'
choice of local keyboard control or MIDI. You can do this yourself
if you have a little experience with electronic repair and the
of wires and circuit boards. If not, you can ship
the unit to Synhouse L.A. for a quick, low cost Factory
For self-installation, it is best to print these notes 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, it is best to completely read and understand each step of the instructions before starting. The particular installation on which this document is based was on Moog Minimoog serial #10796, other revisions may be different.
All repairs and modifications made
to your instruments
will be done at your own risk and Synhouse Multimedia Corporation
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!
1) Be sure
to have the correct tools
and supplies for for the job. If you do not have them, get
them. You will need a regular size Phillips
screwdriver, a smaller size Phillips screwdriver, needlenose pliers, wire cutters or other flush cut nippers, a hobby knife such as an X-Acto,
scissors, a soldering iron, solder, and some heat shrink tubing or electrical insulating tape. If you intend to mount the DIN jack on the back panel with the rest of the jacks (highly recommended), you will need to use a chassis punch (a small hand tool that safely cuts a clean hole in a metal panel) or step drill (a cone-shaped drill bit with many steps on it from small to large) to make the hole for the DIN jack, and an electric drill with a 3/32" or similar size drill bit to drill holes for the 4-40 hardware used to mount the DIN jack, and also a 1/4" or 5/16" drill bit to make a pilot hole to start the chassis punch. The correct size for mounting a MIDI DIN jack is 14.5 mm metric or 5/8" SAE (.62"/15.9 mm) in American sizes. A chassis punch may be purchased from any good tool or hardware store. If it is more convenient, a punch may be mail ordered via internet or telephone from Mouser Electronics at http://www.mouser.com or (800) 346-6873. The Mouser part number is 586-3803 for the name-brand Greenlee 730-5/8 (about $30). The cheaper house brand part number is 380-0145 (less than $20). You will also need an 11 mm wrench (for Greenlee) or 1/2" wrench (for the Mouser house brand punch) or adjustable wrench to turn the chassis punch while cutting the hole. If you choose to mount the DIN jack in the soft wooden portion of the Minimoog chassis, ordinary household drill bits for wood will make the hole quite easily, and will also make the holes for the screws as well, so no chassis punch, electric drill, or drill bits are needed for this alternate quick mounting method. An automatic center punch would also be useful. This is an inexpensive spring-loaded pointed punch that can mark your drilling spot without the use of a hammer. Marking the holes with this small indentation will allow you to drill cleanly without slipping and scratching the synthesizer or drilling through your knee.
Always wear eye protection such as safety glasses when working with power tools, cutting tools, or punching tools.
The Minimoog has no regulated power supply
of +12v DC or greater as required by the MIDIJACK, so the
DC power supply must be used. To stabilize this power, it is
recommended that a 100 uF/25v (or greater) radial-lead electrolytic
be added to the MIDIJACK board. Such a capacitor
is readily available from any electronic supply store, even Radio
Shack with their part number 272-1028.
test the Moog Minimoog to
be converted to MIDI. Be sure that all functions such as the envelope
generator work and that the
instrument plays in tune while playing along with a known well-tuned instrument such as a newer digital synthesizer or sampler keyboard. If it doesn't work properly without MIDI, it certainly won't work with it.
caution should be taken
while working on the Moog Minimoog. The unit should be unplugged
while open and even then, the power
supply may pose some electric shock hazard due to residual voltage in the power supply.
4) To open the case, lift the control panel section of the Minimoog up and support it by inserting a yardstick or similar item under it. Remove the screws holding the rear aluminum panel in place and remove the panel. Remove any dust and debris that may have accumulated inside the instrument over the years. Removing this panel will expose the Mini Moog Board No. 2 where all of the electronic work will take place. A photo called Minimoog-pic1 shows this:
5) Remove Mini Moog Board No. 2 by removing the two retaining screws and gently pulling the board out of the two edge card sockets holding it in place. Once removed, the synth will appear as in Minimoog-pic2:
size drill bit for the switch
stem and two screw holes is 9/64", and the perfect size for the scale
adjust trimpot is 3/16". Drill the
holes. Before mounting the MIDIJACK board, you must make a modification to accommodate the unusual power supply of the Minimoog. The Original MIDIJACK gets power to operate from the synthesizer in which it is installed. Although the MIDIJACK has a very high-quality regulated supply of it's own which allows it to operate with an unregulated input, it is preferable to use the regulated supply inside the synthesizer when available, and it almost always is. In the Minimoog, there is no regulated voltage +12 volts or greater. It has only a +10v regulated supply. To install a Original MIDIJACK in a Minimoog, we will later connect the MIDIJACK #2 red wire to the unregulated DC power supply (which will be fluctuating somewhere around +20v). As an extra precaution to help stabilize any voltage ripple which may become audible in the form of unwanted vibrato in the CV, two solder pads have been placed on the lower side of the MIDIJACK board to solder a 100 uF/25v (or greater) radial-lead electrolytic capacitor in place, upside-down, under the board. The pads are on the end of the board nearest the header for the wiring harness and the positive side of the capacitor should go in the square solder pad marked with a + on the silkscreen. Carefully solder the capacitor in place.
12) The MIDIJACK #1 black and #2 red wires must be soldered in place to get the ground and power for the MIDIJACK. The MIDIJACK #1 black wire must be connected to pin 2A on the left, the ground pin, and a convenient place is on the protruding lead of a component less than an inch from the edge. Solder the MIDIJACK #1 black wire as shown in Minimoog-pic10:
MIDIJACK #5 yellow wire and
#6 green wire are not required for for adding MIDI to an S-Trigger Moog
such as a Minimoog, but it is a
good idea not to permanently cut these
wires off, as an alternate installation method may become useful
later. It is best to wrap the ends of
these unused wires with heat shrink tubing
or electrical insulating tape and bundle them with the other wires when
finishing the installation.
that all connections have
been made, carefully check over your work and examine all soldered
connections for possible short circuits before closing the instrument.
The MIDIJACK hardware packet
nylon cable ties which can be used to tie the MIDIJACK wires to the
Minimoog wire bundles to prevent them from moving around inside the
case. Secure the wires, then remount the board in the edge card sockets
and secure with the two original screws.
chassis and replace the
19) Test and
calibrate using the
procedures described in the Original MIDIJACK Quick Installation Manual.
20) It is
probably a good idea not
to use the Minimoog built-in local keyboard or oscillator CV and
input jacks while MIDI is activated
or vice versa.
21) This installation can be completed
in as little as one hour, depending
on how you mount the MIDIJACK board
and DIN jack, but extra time spent making a perfect
time well spent.