Following on from this thread: http://www.xjbikes.com/Forums/viewtopic ... rt=15.html tumbleweed_biff has sent me his dead TCI to (hopefully) repair. So we have this: The already diagnosed blown driver transistor: Underside: Time to remove the ceramic thick film board and the electrolytic capacitors: The main part of the board is fine: Not so good for the board under the heatsinks: So that's it for tonight, tomorrow will be time to clean up the board with acetone and re-solder the existing components in the undamaged area. The damaged are will need a lot of work, as once the board has been burnt it will conduct instead of insulate causing future failures. Options to consider are isolating that section, or carving out the board. I may repair the undamaged section first, and make the transistors a separate board/heatsink. That would be the quickest way to test that the circuitry is functional before committing too much time. Common faults on these TCI units are normally fractured solder joints and aged/leaking electrolytic capacitors. This sort of failure will probably have an external cause (currently unknown).