switch sense circuit causes blackout to MCU

[krazydarcy]

Hi. I am having an issue with my board and am posting to find out what the cause of the problem is while awaiting a second kit I ordered so to avoid the problem when constructiong that one.

Under certain circumstances I get a white screen but not because of the LCD pin headers (I troubleshooted the soldering of those using J4 as test pads using a proper scope - seeing data in person on a scope for the first time was intireesting ).
If the Coupling switch is set to GND, or Sens1 set to 1v/div or Sens2 set to x5 the screen goes white and when i flick back to one of the other positions the unit reboots.
I have replaced the onboard switched with double pole 3 position rotary panel mount switches and thought the problem was my wiring but redid it three times and made no differance. The reason for doing this with the switches is I have been making a 3d printed retro styled case for it (think 1940's/50's look)

Examining the schematic I see that all the problem settings connect direct to ground on the position sensing circuits and by disconnecting one of the wires was able to confirm its related to the sensing circuit but can't figure out why? My switches are plastic housings so don't have the pin holes at each end connected The three pin groups to the 3 positions while the 2 pin group go to the double poles as depicted in the schematic that came with the kit. It appears that when any of the three switches are set to the position that connects to ground it is shorting out the power supply. when this happens AV- AV+ +3.3V +5v are all reading less than 1v each. with the other positions they read correctly. I have done a number of projects with arduino dev boards and connecting an input to ground simply "pulls it down" so it gives a reading of LOW if digital or 0v or close to it if analog - which is what the sense pins are here - analog inputs. This is how we can use analog inputs to handle multiple switches.

I need to know why this is happening so I can avoid the problem with my second kit (and investigate if its worth trying to repair the first.
Thank you for your time.

Attached is a photo of the sticker on my board.

[krazydarcy]

Good news,

I found the problem.

If you look at the switch contacts on the pcb they look like this:
O O O O
O O O O

as the pins are not numbered on the pcb I had assumed the single pin hole to teh right was the common wire and had wired up accordingly.
I just got home from work and probed one of the slide switches that came with the kit.
The switch pin-holes are (as numbered on the schematic)
4 3 2 1
8 7 6 5

where 2 and 6 are the respective common wires for each pole of the double pole slide switch.

I quickly unplugged one switch and reconnected it
No black out - this was because pin 5 can no longer short to pin 8 due to the way I had wrongly wired it up.

I have posted the cause in case anyone else is wiring up their own slide/rotary switches to the pcb.
Have to go and rewire the other two switches

Thanks.