Sunday, 25 August 2019

MIDI Thru Box

Finally, I closed the lid on the MIDI Thru Box I was working on for a loooong time.
Not that it was particularly difficult.  I really was a slacker on this project.

Testing the finished product

Validation on the breadboard.

Printed Board Assembly
I took the basic schematic from the very good Papareil Synth Lab MIDI page (sorry for the french).  You'll find schematics and layout at the end of this article.

I chose to slightly modify the original to have 5 outputs out of the 6 inverting Schmitt trigger of the 74HC14.  The input LED indicator is driven by a transistor.
As I wanted to power the circuit with a standard pedal power supply (9V - center negative), the circuit has its own 5V voltage regulation.

Bob cleans the mess during drilling

Circuit assembly went like a breeze.
Drilling the box needed a bit of attention with the small M3 holes next to the big ones for MIDI jacks.

Drill box

As I assembled the whole, I noticed I didn't pay enough attention of the thickness of those MIDI jacks.  The electronic circuit could barely enter.  The last connections were not easily soldered.

I didn't see how I could test it without putting everything in its final place.  I really was worried about a possible debugging session.

My poor ESI MIDI interface gave me the creeps as I was testing.
But finally, all went fine and I found no mistake to correct.

Testing with a couple of Korg Volcas

As promised, the full schematics :