The small board (which still works) has 3 caps - but, it works.
The large board (which doesn't work) has 3 - but they all have ~12v going through them.
There are also two things visibly failing here, the back-light and even when that's independently powered, the LCD panel. Both these circuits are very different, and appear to have very large ceramic caps already.
I'm not convinced the OS of the NAV unit will be separate either, there's only one "media" CPU and it's the same type on both boards. Also, the NAV button doesn't appear until after it boots and works out NAV exists - and the two buttons at the bottom change to three. If it were separate - it would know NAV exists and never need to show two buttons only. Also, I can't see SWS making two completely different OS's - but I imagine the NAV part is an application that exists in the larger flash memory that is automatically run at startup.
I had a read about QNX - it's a proper operating system. It has drivers (well, this would be a custom board, so drivers were written for QNX for the hardware things attached)... It has boot sequences... Part of all this is the driver initialisation process. My current thinking is, one of the "device" chips (bluetooth, usb, video-input) has died and the driver is "waiting" for it to respond before allowing the boot process to continue. It's not likely to be fault tolerant like a PC would be with timeouts for failed hardware - quick and dirty software probably to "get things done" only. This, I hope, I can find with my logic analyser but it's going to be a slower process than I had thought with simply fixing a bad regulator. There's a couple of I2C repeaters that will be first on my list. I'm still yet to find the 21v source for the back-light too!
My budget
ICC with NAV came today - it has maps "19" on it :(
Most of the silver buttons are in good shape though (not all) but between the two I have, I can make one really good unit.