[Bob Quintal]

" wrote in
:

on the board. Everything is soldered on one single board. There
is nothing and bench technician can do to fix the problem

Baloney!



Competent bench technicians can repair solder joints, and replace
bad

components soldered to printed circuit boards.



If the problem is diagnosed as a RoHS compliant (e.g. brittle)
solder

joint, it may be easy for a competent technician to fix.



If the problem is diagnosed as a bad resistor, it may be easy for
a

competent technician to fix.



Q



Dah..........
And how exactly bad solder joint can cause EXACTLY THE SAME
PROBLEM in 4 different units?


One of many possibilities is that one batch of a part (resistor,
capacitor or IC) may have a defect in that a solder pad on that lot
of devices was contaminated with some oil. That part is used in one
place on each board. so each board will have the same problem after
the solder joint corrodes about 4 years after being soldered.

I've seen it happen.

--
Bob Q.
PA is y I've altered my address.