It has been said that 80% of mechanical/electrical/etc problems are due to easy-to-find faults, and I believe this is largely true of our older vacuum tube equipment. If a fault is not quickly found, things can become difficult (think silver mica disease within an IF can). But with the advent of digital and computerized gear, much trouble-shooting has required depot-level equipment and facilities to a large extent.
But some of us have vacuum tube or analog solid state equipment that occasionally needs attention, so perhaps the references made available below will be of help.
