Quoted from stumblor:So I've had a bit of a look through the schematics, and there's really not that many components that could be the cause of it. I still have a suspicion its one of the fuses (might be worth checking these again), otherwise the only thing it could be is the the bridge rectifier at BR3 or the cap at C8. My guess is the bridge rectifier.
https://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Low_Coil_Voltage
Few questions:
- Did you measure idle voltage at the coil (ie not energized)
- can you measure resistance of the entire circuit taken from the power board connector. There's almost nothing between the power board and the coils, you should see a value of a few ohms (careful with the direction, the flyback diode can affect the reading). A typical coil is about 3 to 4 ohms. A higher resistance will result into a lower current, thus reducing the magnetic effect. Likewise a lower voltage than expected (should be 70V) decrease current for a fixed resistance value
If your voltage level is too low, issue is likely the rectifier (but then all coils on the same power rail should exhibit the same behavior)
If your resistance is too high, there 's something in circuit raising resistance. Check solder connections and wiring, especially at the connectors
Control transistor might also be bad, although to be fair I'm not quite sure I understand how a transistor could' partially fail (ie switching, but limiting current)