10 Apr
2008
10 Apr
'08
2:46 p.m.
The book the poster on the other related thread is
probably thinking about
is Larry Pina's "Macintosh Repair and Upgrade Secrets", which Tony
probably disapproves of. :-) Pina discusses and recommends replacement
of components based on the items which, in his experience, most often lead
to certain symptoms. He does not discuss doing an actual probe and
diagnosis to determine the failed component, which is why I good naturedly
refer to Tony's disapproval.
And you'd be right :-). It's what I call 'lucky dip servicing'. It may be
useful if you have lots of similar machines to repair, or if you run a
repair shop, or similar. Perhaps 95% of the time the book will get it
right, or rather the most common failure is what's gone wrong with the
machine on the bench.
But that other 5% of the time, it'll be wrong. And becuase the book
doesn't explain the reasoning behind the diagnosis it gives, it won't
help you find the real fault, even if the real cause is a component in
the same part of the circuit as the one you've just replaced based on
said book.
I must admit that just abotu every repairer uses a bit of this 'lucky dip
method'. There'll be common causes for problems that he'll check first.
But a _good_ repairer will know how to continue if none of those are the
problem.
Incidentally, had the original machine been a Mac+, I could possily have
helped, as I've worked on those and have a fair idea how the analogue
board works. But IIRC the SE/30 is very different, and I don't have one
of those to look at.
-tony