Here’s my Kosmo DSO138:
(My display is a little cockeyed on its PCB and there’s not enough play for the mounting screws to correct it — maybe I’ll drill out those mounting holes a little sometime.)
Slide switches, tactile buttons, and trigger indicator LED are mounted to an auxiliary PCB mounted behind the panel. Also on this board are a Eurorack style 10-pin power header with 10 µF caps and power reversal diodes, and a 9 volt regulator and TL072 op amp with associated passive components.
A BNC jack and a 1/4" phone input jack are mounted on the front panel. A toggle switch selects whether the scope input is connected to the BNC or to the 1/4" jack signal after being buffered with the TL072. The latter signal, buffered, also goes to a second 1/4" panel mounted jack, so the signal can be passed on to another module.
Also on the front panel is another toggle switch, controlling the 9 V power. (It’s good to power off the scope when not in use, for at least three reasons: the scope draws about 130 mA current on the +12 V rail, it probably puts out some digital noise you don’t want getting into your synth sound, and leaving it powered off when not in use will help extend the life of the display.)
The main DSO138 board is mounted perpendicular to the front panel. I used a 3D printed carrier and long spacers to attach it. The display board is parallel to the front panel and connected to the main PCB with a ribbon cable. More ribbon cables and a couple wires connect the auxiliary PCB to the appropriate points on the main PCB.
Design files, Gerbers, STL for the mounting fixture, and docs in the GitHub repo:
I’ll put my extra boards and panels up for sale on Tindie sometime soon.