petrus bitbyter wrote:

In the days that PCBs were expensive, so you could take an hour or more to
pinpoint the fault, our techs used an hair dryer and a can of coolant.

I don't think I understand: what did they use a hair dryer for? If it were
hot enough for melting solder, its manufacturer would probably get in
trouble with the intended customers.

Of
course, experience was the other half of the requirements. The latter
faded away when the repairtime/board shrinked. I still own a working XT of
which the motherboard was rejected as the fault could not be located
within half an hour. I got it for a small contribution and made a running
machine in one evening. These days PCB repairs are rare, very rare. That's
to say for professional/commercial use. Even boardswapping becomes too
expensive in some cases. It has been six years now I bought a monitor.
Within warranty time it was swapped as a whole. After three years, when
warranty was over, it was said to be unrepairable and I was advised to buy
a new one. To make a long story even longer: Cans of coolant are still
available but I'd use a hot air soldering "iron" for the hot part.

I didn't know these things existed. How can hot air (plasma?) be more
localized than a thin metal stick?

Regardless, I wouldn't want to spend $500-2000 on something that won't help
me localize the problem anyway.

Components became very small you know. Besides, you'll need lots of time
and even more lots of luck. Nevertheless it may be worthwile to give it a
try. Good luck.