23 Nov
1999
23 Nov
'99
11:19 a.m.
-----Original Message-----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Tuesday, November 23, 1999 9:06 PM
Subject: Re: Oscilloscopes
most
I agree but I would not recommend someone dropping a couple hundred bucks to
fix an old 20Mhz scope as I am sure they would not limit their use
*exclusively* to vintage minis. A 20Mhz scope in RF/High speed logic
troubleshooting/design is totally useless. A 20Mhz scope isn't even very
good at looking at the color burst of a video signal in any detail. Again, I
find most folks design/troubleshoot in a variety of areas and that's why we
need scopes with all the toys. I don't see Tek making any more 20Mhz boxes.
> It's rare that I do. Used to have a 465B,
didn't use it enough to
warrent
maintaining it
or it's weight. While the book calls for a better scope,
I know the 20mhz B&K would be more than enough to track 8F core problems
Sure... But if you're buying a 'scope, it makes sense to get one that
will do all that you might need. So while you don't need a 50MHz 'scope
or whatever to sort out 8/f core memory, you might find it worth getting
one for other work.
> as I used it to set the slice time. Then again, I know how to get the out of a scope
too.
Oh sure...
There are some people here (you're certainly one, I like to think I'm
another) who (most of the time, at least :-)) understand what we're
trying to look at and understand just what our test gear will do when
given a strange signal. We know what our '20MHz' scope will do with a
30MHz signal. And we know how to push the instruments a bit.
You don't _need_ expensive test equipment. I've done a lot of fault
tracing using a cheap analogue multimeter and a Radio Shack logic probe.
And with those 2 instruments I managed to extract enough clues to the
fault to replace the fault component first time (most of the time).
However, I am also sure that there are people here who could use some
more clues as to the fault, who can't interpret every last piece of
information that they can get from simple instruments. And those people
generally make use of rather more instruments, which perhaps aren't
strictly necessary...
Don't get me wrong -- there are times when _I_ find a 'scope essential.
Perhaps if I was more clueful I'd not need one then either, but I do. But
I've also discovered that _very_ rarely do you need a new and expensive
piece of test gear to fix a classic computer. Most likely you can do it
with what you already have if you think about the problem.
I was discussing a related subject with a friend
earlier this evening. We
came to the conclusion that experienced hackers (this was actually about
mechanical engineering, but it applies to electronics as well) can do a
lot of good work using 'scrap' components and a few tools/instruments.
But beginners probably should use new (and known-good) components and
have rather more instruments. Of course it's often the other way round --
beginners don't have the money to spend on a hobby they may not continue
with, while experienced people have obtained a good collection of tools
and test gear over the years (and really know how to use it!).
-tony