The making of the Roland Junior-106
Since the power supply wouldn't fit inside the shrinked chassis I had to create a small power distribution card to send the seven incoming voltages to the four destination cards inside the unit. I also had to make sure that the cards were sufficiently isolated from each other, and most importantly, I needed to create the Junior-106 transpose circuitry. Having lost the lower half of it's keyboard the Junior simply wouldn't be able to play those funky bass lines anymore. Without having access to the CPU code for the Juno (my unit is a 7811-type, with internal masked ROM) my only option was to create a switch circuit that could transpose the keyboard signals three positions down. Each position moves the keyboard down by 8 semi notes, so 3 x 8 equals two octaves.
Close up of the power distributor, just a copy of the one
on the PSU board. One connector for each of the four boards
Test run. All still OK... Phew
Better safe than sorry, some thick plastic to make sure the Jack
board doesn't accidentally come in contact with the Panel board
When mounted, the Jack board have 3-4 mm clearance from the keyboard springs and about the same to the Panel board. Perfect!
Next: Transpose me!