Repair skills: where did you learn hotair and board-level work?

Dead hashboards are half the second-hand market. For those doing their own reflows and chip swaps, how did you learn without killing boards?

Bought a box of known-dead boards and practised. Killed three, fixed five, net positive.

A cheap microscope changed everything. You cannot fix what you cannot see.

Second this. undervolting bought me 6% efficiency for a small hashrate haircut, and I'd do it again.