New Definiton REQUIRED

From: Tony Duell <ard_at_odin.phy.bris.ac.uk>
Date: Mon Nov 17 14:16:25 1997

On Mon, 17 Nov 1997, Allison J Parent wrote:

>
> <> > latest thing to come down the 'pike - it's all ASICs, custom silicon,
> <> > and surface mount stuff on wafer-thin boards. In short - not built
> <> > to last. Nor is it designed to.
>
> Surface mount offers compact and also better signal integrity for ultrafast
> logic. There are many good reasons for surface mount that are in the realm
> of quality improvement. Yes, it's take more skill to fix and some of the

IMHO, surface mount repairs are not that hard given the right tools - a
temperature-controlled soldering iron with a fine tip, fine silver-loaded
solder and a steady hand will suffice for most repairs. You don't _need_ a
hot-air rework station - such a unit will make the repairs faster, sure,
but not necessarily any better.

Don't try to remove the old component in one piece. Cut off the pins
(_carefully_), remove the 'body' and desolder the pins one at a time. Mind
you, I tend not to remove pin-through-hole devices in one piece unless I
know the device is rare and/or I am removing it to dump the contents. When
I repair something, suspect TTL devices get removed one pin at a time -
OK, so I may be replacing a few pounds worth of chips that were OK, but at
least the PCB will survive.

> parts are not easy to come by.
>
> FYI in the industry there a few descriptions of part of the problem.
>
> Good, fast, cheap, pick two.
> Cost of repair exceeds value of unit. Fix/trash decision.

What is a problem is when it was decided at the time of manufacture that
it was cheaper to replace than repair, so service manuals were never
available. Now, 10 years on, there may be no chance of finding a
replacement, so you have to repair. And repairing something without docs
is the second-worst job that I know (the worst is repairing something
with an incorrect/incomplete manual!)

Case in point : Zip drives. I won't use one because no service manual or
bit-level description of the disk is available. At some time in the future
all the drives will have died. And then there's no chance of ever reading
a zip disk again.

> Allison

-tony
Received on Mon Nov 17 1997 - 14:16:25 GMT