circuit board damage assessment

[Abe]

I'm a newby, sort of, so pls ignore my possible ignorance. I didn't study engineering, but I studied physics and  was a hobbyist. Then, electronics recently became a source of income. I'm still uncertain when it comes to being absolutely sure that a board has been fully restored. l work on fairly high-power circuits like 3-phase VSDs, so the client can't always give me the whole device to troubleshoot, just faulty sections of it, usually with water damage. How do I make absolutely sure that I've found all the damaged components BEFORE connecting the board back into the system and powering it up? I can't always simulate ideal test conditions. Is there a clever method, or is this just the nature of the beast? Also, I can't always confidently identify SMDs by the packaging markings.

[cur8xgo]

I'm a newby, sort of, so pls ignore my possible ignorance. I didn't study engineering, but I studied physics and  was a hobbyist. Then, electronics recently became a source of income. I'm still uncertain when it comes to being absolutely sure that a board has been fully restored. l work on fairly high-power circuits like 3-phase VSDs, so the client can't always give me the whole device to troubleshoot, just faulty sections of it, usually with water damage. How do I make absolutely sure that I've found all the damaged components BEFORE connecting the board back into the system and powering it up? I can't always simulate ideal test conditions. Is there a clever method, or is this just the nature of the beast? Also, I can't always confidently identify SMDs by the packaging markings.

You need to design tests that can evaluate the board function out of the unit. For things you can't evaluate directly because they need to be in-system or you have no way of simulating real world conditions, you need to come up with some rationale as to why that particular sub circuit or component is good to go..for instance if the board normally operates at 300 billion amps inside a nuclear reactor you cant really simulate that..but you can sign off that you replaced all the components that are involved in switching that high current and you also ran some tests proving that they have some functionality. Thats the best you can do and compromises like that are done every day in every industry.

If the clients you are doing this for have any kind of formal quality management system they are either checking your work anyway or they would require you to adhere to strict, risk managed procedures for rework and verification. If they dont have a quality system then whatever you come up with here is probably going to be better than what they use to make sure they don't install broken stuff anyways.