Ghost pressing of L+R? Boots straight to activating camera

[vinnieb]

Hi All,

Hopefully the right place to ask this one! Bought a 3DS to fix up from ebay as a fun project for myself to learn some more. Thought I was doing well after finding disconnected speaker cable and getting it to boot, but one problem still remaining.

As soon as it powers on, I get either the home screen constantly scrolling to the right, or going straight to 'activating camera'.

Initially I thought maybe a stuck circlepad, dpad, etc as if I pressed one of those it would interrupt the signal. But, disconnected what I can and still no joy. Took the contact pads off the dpad too and all clean there (you can see in pic).

From what I understand pressing L+R buttons would be a shortcut to activating camera, so seems more likely somethings up with those. But what I don't get is that how thats happening even after disconnecting them from the board.

Added some close ups of their connectors, I've cleaned with isopropyl, rest of the board looks good from what I can see.

Anything software that could cause it? Otherwise can only think to try and find a replacement main board. Attached pics of board front + back and close ups of L+R connectors

Edit to add, found the pinout for those two connectors, incase there was a short making it always pressed. Sadly no luck, all ground pins apart from pin 3 and pin4 on the left/right connectors.

Also don't seem able to boot into safe mode, with or without the l/r buttons connected back up.

Thanks for any suggestions!

 

[vinnieb]

Had a chance to investigate a bit more.

Tried giving the board a bath in isopropyl, just on the off chance of something I'd missed. No change.

But I do get more varied behavior, for a while it was going straight to update menu as if Up and X pressed as well as the LR.

I'd been assuming maybe software or something else, as continuity checks didn't show anything.

But actually, checking voltages at the TPs for these buttons, something is up - they're measuring more like 0.5V rather than the 1.8V on other buttons. And disconnecting the board and just checking resistance with nothing powered up, they are on notably lower resistance (in the k's rather than M's).

Ah that was it, some of the resistors for these buttons had gone out of tolerance I guess. Just bad luck it happened to be on pairs that forced it into a problem mode. Taken the resistors out and seems alot happier now.