Troubleshooting RAMPS v1.4

G'day!

I'd appreciate your help figuring out how to fix my RAMPS v1.4 board after I replaced the stepper motor and thermistor headers and re-soldered a broken connection to the F2 fuse.

Symptoms:

• If I plug any stepper motor drive into any position, the Arduino fails to boot
• I can't sense the temperature of extruder 0's thermistor any more

Things that seem fine:

• I have good connectivity pad-to-pad across F1 and F2
• I have solid 12V power to X4
• I have good connectivity between the 1A/1B/2A/2B headers for the drivers and the matching pins for the stepper motor connectors
• There's no bridging between adjacent pins on the stepper motor connectors
• None of the stepper motor pins seem to be shorted to either the Arduino GND on the double-header on the end of the board, or the grounds on the 12V supplies on the other end of the board
• Pins 2, 4, and 6 on JP7 connect to the far side of their matching capacitors
• Pins 3 and 5 on JP7 connect to the near side of their matching capacitors

Things that don't seem fine:

• Pin 1 on JP7 does not connect properly to the near side of its matching capacitor: the resistance ramps up like there's another capacitor there. My multimeter measures JP7:1 to C5 as 16.4uF. C5 itself measures as 10uF. C8 and C1 measure as 20uF.

What should I check next to figure out how to resurrect this board? Before I re-soldered the connectors, it could control extruder temperature and drive the stepper motors.

Thanks,
Garth.

top view (large)

back view (large)

Ok, I think I've just about massacred JP7:

(large)

The tracks around pins 1, 2, 4 are OK.

The track around pin 6 is marginal.

The track around pins 3, 5 are almost destroyed. There's just enough at the top to connect with the multimeter. I hope this is something I can fix with a little solder paste; otherwise I'll have to try to solder new lines to the near sides of C5 and C8.