Supplemental files... DG-10 to DG-20 MIDI conversion

Ok...this is simply going to be all the files...I will try to organize them by section...starting out with the MIDI conversion.

This is what I used to do my mod.

First it is very handy downloading the DG-10/20  Service Manual available many places... 

On all the documents I annotated the original wiring in red (so I could follow the circuit) and my changes in pink (basically as an assembly manual).

The most time consuming part was the re-engineering...but soon I realized that the schematics almost exactly matched the circuit board...so you could almost lay the schematics over the board to identify parts.

In my reverse engineering I reversed the pictures of the bottom of the circuit board so it would directly match the top of the board...and the schematic...it makes sense once you try it.  As a result some of my notes are in backward writing, but it is easy enough to figure out.

Lets start with the schematic.  

First starting with the MIDI port on the DG-20.  There is a switch to either have 6 channels out...or just all 6 strings to one channel.   Second is the port itself.   Note the identifiers JG-1 through JG-6  This is on a daughter board at the IO jacks...I had to just wire it up direct.  (BTW the item marked FB...those are ferrite beads) (I used DigiKey part number 240-2513-1-ND Ferrite Bead 86 Ohm Axial)  Also on the circuit below, there are two things that look like black circles spit in half...they probably match something on the circuit board that would have been mounted on the DG-20...I couldn't even see a photo of that board...the fully split in half one means not connected...the one with a small line in the middle is connected...

 Now on this schematic on the upper left side you again see JG-1 through JG-6 , these are the drilled holes in the DG-10  circuit board...they aren't marked...and I did have to modify them a bit...but it is almost 100% there.  So I ran wire from those drilled holes to my MIDI connector and switch.

Now you will note on the DG-10 schematic the obvious missing JG connection.  You can see in pink the required mods...one specific one tells the CPU that it is a DG-20 not DG-10

So here is what it looks like on the DG-10 circuit board.

 Inverted backside with mods  You will note I marked the connection 1-6 on the upper right side.

BTW all the jumpers and components go on the top...but it was easier to follow the circuit by drawing it out on the bottom of the board.

Actual view backside with mods, again red is existing wiring, pink is my mods.

These photos have ALL the mods in view, not just the MIDI...so just using the schematic, knowing where i marked pin 1 and 6, just follow the lines... There is one wire to remove, a resistor to add, a diode to add. and a handful of jumper wires to install...almost everything goes into existing drilled but not marked holes.  Now for the pic below, note the wires at the lower left of the above pic.

 Here is the only circuit trace you have to cut...right there in the center of the pic above next to "JD" you see I have a pink line and 3 white lines...that area is one big circuit trace, so I had to cut it where those lines are to separate the area into separate traces...the white is where I dug through the copper trace to bare circuit board below.

Finally I needed to know what pin is what for the MIDI connector.

Going slow and using a voltmeter in 'resistance...beep' mode I went through it line by line, making sure I had a match from the schematic to my DG-10 wiring.