I'm waiting for a new HDMI LCD to arrive before I finalize this design.
R30 relocated closer to Q6. DONE
Finally fixed bug with GPIO25 and GPIO24. 8-( DONE
Fixed Rotary Encoder not connected due to not being aligned to grid. 8-( DONE
Changed package for Q1-to-Q6 transistors to ones where the pads are further apart. Matches part from LCSC.
Added mounting holes for KYV-N5-V1 HDMI LCD Driver board.
Added mounting holes for 66.5 x 46.5 LVDS Driver Board (guestimated the position).
Added mounting holes for 65mm switch board.
Changes in V3.1
Pi is a bit too close to the power supply, hard to remove microSD. Fixed in V3.1.
Changed the package for the BC547 to that of the BC335. Just very slightly easier to solder. Fixed in V3.1.
R2 is on the wrong side of the board. Fixed in V3.1.
exec light should be below the exec button. Fixed in V3.1. Note: Button is moved slight higher, but should still work with the FMC 3D model.
DEALBREAKER: GPIO25 wrongly labelled as GPIO24 in V3.0, resulting in 16 dead keys. Fixed in V3.1.
Relocated all the backlight resistors and all the diodes to the area just below the screen. Easier to find, although the autorouter has a tougher time.
Shifted the mounting holes for the LCD driver to align it with the LCD ribbon cable position.
added two holes to zip-tie the VGA-HDMI adapter down.
Changes in V3.0
Added socket for Raspberry Pi Zero WH. You can either plug a Raspberry Pi Zero WH directly into this socket, or use a 40-pin IDC ribbon cable (if yo solder male pins) and extend it to any 40-pin GPIO Raspberry Pi model of your choice.
Added socket for MP1484 switching power supply module (https://goo.gl/Xku2Xa). This can be set to step-down 12VDC to 5VDC, suitable for powering the Pi. With this you only need a single 12VDC power supply to power both the Pi and the Display.
Added output 12VDC power connector for the LCD Display.
Added pull-down resistors for the LED indicators, so are off on power up, until driven by the software.
Replaced the switches with LED Push buttons (https://goo.gl/gbQCQg), so we can backlight the keys. LEDs are driven by 12V with a resistor for every 3 LEDs. I've used the yellow version of the switches LEDs with Vf of 2.0V and 330R resistors. If you are using the white LEDs, replace them with 120R resistors.
Added software-controllable dimming control of button backlight, using the Pi's built-in PWM output.
Added Rotary-Encoder input to Pi, to control dimming.
Removed hole for LCD, it's easier to mount it with double sided tape.
Added mounting holes for LCD Driver under the PCB.