I have a faulty controller that I'm trying to fix.
The first test I did on it was to test the resistance between the phase wires and the main power cables (thick red and black, +72V, GRND). Between the ground and the phase wires I got about 10KΩ on each. Between the red and phase wires I got Y - 0.5, G - 0.4, and B - 0.3, all indicating that the FETs at least were OK. On a previous occasion, I had connected it to the bike cased, and found it was dead when I applied the throttle.
For the next test though, the board was out of its case, but lying on a plastic sheet to prevent shorts so I could test the board with a multimeter. Everything was plugged in except for the brake cut-off, which I hadn't bothered with for now.
The controller was fine when I plugged in the main power. However, as soon as I turned on the 'ignition' - supplying the controller's power feed (small red wire), there was a crack as something blew.
This had happened:
http://zenid10.files.wordpress.com/2010 ... 0x1200.jpg
It turns out that though only last FET was visibly scorched all the Bank C FETs were dead, - all the legs of the FETs on Bank C now showed continuity both within them and between them. I can't figure out what caused this to happen, One theory was that condensation had gotten in through a space left when the board hadn't been slid in all the way, but others have said that a bit of condensation is unlikely to cause a FET to blow. The other theory is that this is a symptom of the actual problem. But what could cause the whole bank to fail when being powered up by the feed?