The onboard chargger OBC troubleshooting thread has technical circuit board details, but this thread is intended to be a simple HOW TO for fixing the OBC.
The technical investigation is still in progress, but circuit details are not of much practical use for most folks.
So far it seems that only a few components have blown in failed OBCs, and skylogger has successfully repaired 2 units by replacing these parts.
What typically Blows or Fails?
#1. The 20A fuse in the MCU.
#2. The high voltage snubber capacitors.
#3. The ceramic pre-charge resistors on the Neutral line.
#4. The AC input relay on the Neutral line.
Why are these failing? We don't know exactly, but it appears that:
F1. Anything that could suddenly interrupt normal charging (e.g. pulling the plug, mains power outage, etc) will cause large voltage spikes in parts of the circuit to blow #1 and 2 above.
F2. Any disruption of the internal low voltage supplies (weak or old Aux battery, bad relays in fuse box, etc), or frosted contacts in the AC input relay, will blow #3 and 4 above. In addition this could cascade to cause a sudden interruption while charging, i.e. F1 above.
If there is sufficient interest, then i would consider a bulk order of these parts to put together a little repair kit.