How does advance repair looks like? Raymarine S3 autopilot computer. No motor outputs.
Outputs are controlled by H-bridge which consists of N channel mosfets and logic which consists of 7400 TTL series which is fine in this case. For N-channel mosfet to turn on voltage on the gate needs to be bigger than the voltage on the source. To achive that most modern circuits are using bootstrap circuit, but this one uses a 2 step charge pump. Digging around i found out that problem is in the main MC which can not generate pulse for charge pump. It is internally shorted unfortunately, but every other periphetal is working fine. Unfortunately I don't have spare microcontroller so what is left? Good old LN555 in bistable mode. The only problem is that in bistabile mode LN555 can not generate precise 50% duty cycle, but after some calculations with external components I managed to get it to 49,6% which is fine. Fast prototype on the breadboard and S3 is up and running again. This solution requires production of external PCB with LN555 as frequency generator which I can do, but I won't because it is not worth the time. I just wanted to poke around and see is it going to work. So what should be advance repair, it looks like it is not going to be repair.
