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On Monday, July 29, 2013 5:16:47 PM UTC-5, Bob Quintal wrote:
" 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.

I've seen it happen too many times. And in all those cases I was able to quickly find the problem by lightly tapping on the board and re-solder the joint. Not this time.