> On Thu, 18 Jan 2018 16:53:24 -0400, Leon Fisk
> <
lf...@no.spam.iserv.net> wrote:
>
>>On Thu, 18 Jan 2018 14:56:05 -0500
>>Ed Huntress <
hunt...@optonline.net> wrote:
>>
>><huge snip>
>>>It's disheartening to become obsolete. d8-)
>>
>>Yeah, I use to fix stuff, good thing I retired when I did. Still do
>>for
>>friends when I feel ambitious, which isn't often nowadays. Now
>>people
>>replace stuff, even the "repair" guy...
>
> Yeah, the new "techs" are board replacers because the computer
> diagnostics told them to do so.
>
I was working in the semiconductor industry when surface mount came
out. Circuit board layout became much simpler without the forest of
vias to dodge, especially for inner signal layers on increasingly
dense computer boards. That soon translated into physically smaller
but equally challenging designs.
The pads for drilled holes had to be excessively large to avoid
misalignment between the photoetched copper and the separately drilled
holes. They are drilled in a stack and the glass fibers randomly
deflect the tiny bit as it goes deeper. Boards were rejected if there
wasn't a minimum ring of copper all around the drill hole, because it
wouldn't plate all the way through reliably. The hole is drilled
larger than the specified finished size to allow for plating.
It was recognized that surface mount boards may not be repairable but
the greatly reduced manufacturing cost balanced out the high price of
qualified repair technicians, the overhead of handling returns and the
higher potential of subsequent failure on hand-reworked boards.
Typically a small subset of boards caused repeated trouble while the
rest worked fine until obsolete. About half the field returns I tested
showed no fault on my test system.
I buy, recondition and use older lawn and garden equipment because
it's made of metal that I can repair or copy instead of molded plastic
I often can't. Yesterday I forged a pair of long canning-type tongs
from 1/4" gas welding rod to handle firewood for the stove.
The kitchen tongs I can buy don't last long. Fireplace tongs are
intended to grab the middle crosswise rather than the end lengthwise.
-jsw