> when the FireWire port dies the only repair that is ever proven to be effective has been to replace the entire main board
You aren't talking to the right person... A circuit board is a set of components and wires... With enough expertise, it's always possible to find and replace the faulty component/wire. Someone who says the whole board needs replacing simply doesn't have the expertise.
It would be like hiring a builder to fix a window frame, and them saying "the only fix is to just knock the house down and buy a new one".
Sometimes the expert time required to find the fault isn't worth it when a whole new board is cheap... But that isn't the case here.
I agree with the thrust of what you're saying and OP should definitely take the board to someone who will do board rework and see what they say.
But I don't agree with:
>With enough expertise, it's always possible to find and replace the faulty component/wire.
That depends on what's happened. If it's an ASIC or something else complicated and application specific that's died, then the thing is probably toast unless you can find another board that died of a different cause.
It really depends on what exactly is broken. If it's a BGA chip, it's much easier to just replace the whole board, because almost no one has the facilities or expertise to replace BGA packages on a board correctly. If it's a connector or a capacitor, you can do that with a soldering iron if you have some skill. If it's some little 14-pin SOIC package (with 0.5mm pin spacing) and you have a hot-air rework tool, it's trivial to replace it. Of course, most hobbyists don't have hot-air rework tools (they're not expensive though).
You aren't talking to the right person... A circuit board is a set of components and wires... With enough expertise, it's always possible to find and replace the faulty component/wire. Someone who says the whole board needs replacing simply doesn't have the expertise.
It would be like hiring a builder to fix a window frame, and them saying "the only fix is to just knock the house down and buy a new one".
Sometimes the expert time required to find the fault isn't worth it when a whole new board is cheap... But that isn't the case here.