4. Its blindingly obvious
5. Its dirty contacts
It is amazing how often multi-
6. Beware the dreaded solder crack
If the connectors aren’t dirty they can come loose. A good plan is to gently waggle everything (on the equipment!) with power on and see if it bursts into life, squeaks or flashes or does more what it should. Heavy components, mechanically strained components and components subject to vibration and heat (transformers, relays and connectors mainly) are prone to solder failure. A jeweller’s X10 loupe is a good thing to carry. The cracks are often hardly visible to the naked eye.
7. Talk to as many people as possible about the fault
Talking to machine operators is usually very productive. They may not know the first thing about electronics, but they do know how the machine normally works, and what has changed. They also may admit to things that give a good pointer as to the cause. Since these events may not always be defined in the operating instructions it is most productive to adopt a friendly non-