Greetings! I have become the new owner of a as-is WM-EX677 and WM-F20 on Ebay. From the pictures on the ad, both machines looked clean enough I figured no one had been playing around in them, and the lack of battery corrosion suggested to me that it was pretty likely all they both needed was belts. I hit it on the mark with the EX677, the old belt had fused to the drive pulleys and the backside of the case shell; The F20 didn't seem to be so fortunate. It appears to me that someone had been tampering around in the F20 after all. The tag for removing the battery had been melted to half it's size as well as a minor part of the plastic housing, and I found a loose wire that I'm having trouble finding a home for. A section of circuit ribbon has been crimped over as well. I'm under the impression someone's been in here with a soldering tool before me, and I couldn't find a descriptive enough video online to solve the problem. For those with far more experience than me, how would you attempt to repair?
If I see right, the REF pad doesn't have any wire soldered to it. There must be a wire going there, from underneath the board. The folded over flex, as long as the traces are not open shouldn't be a concern. First things I would check is swiched battery votlage gets to board (leaf swtiches often need cleaning/sanding on these models), then if the DC-DC converter actually produces the output. There are 2 voltages that are generated: +11.5V for the radio PLL and +2.6V for the motor drive circuit.
