*** Ideas needed for developing interactive displays....

From: Antonio Carlini <a.carlini_at_ntlworld.com>
Date: Sat Sep 11 08:50:23 2004

>> This is good, but a clock usually costs less to run than
>> a computer (and a lot less to run than an *old* computer).
>Possibly... On the other hand PCs aren't _free_ to run either,

My point is that once you have rebuilt your clock, it does
not cost much to make it available to the public in good
working order. Put it in a display case, wind it up and off
you go. You'll need to pay for maintenance (and someone to
wind the clocks as necessary) but that's it. Computers
(including modern PCs) come with a power bill attached
(the older, the bigger - in general). Running a PDP-10
would not be cheap. Running Big Ben (if I had the space :-))
would just need me to wind it up now and then. (I'm
ignoring the maintenance costs of both BB and a DEC-10,
because I assume they are both too much for me!)

> > There are also many more people willing and/or able to
> > sit down and understand a clock than there seem to be
> > who are willing/able to do the same for electronics.
> This I don't understnad.

In the UK at least, there has been a long tradition
of mechanical engineering. Add to that, the fact that
many people find it easier to comprehend things that
they can see and I suspect you have the answer.

> Classic computers (at least not any one I've
> worked on) are not that hard to understand.

For thee and me, maybe. But for the majority of people
they are a black box. No moving parts.

>And if I can do
> it, anyone
> can!

Somewhat unlikely. I expect any reasonably practical
person can do what you do with you there telling them
what to do in detail. It's the umpteen years of
experience that you have that help you decide what to
do next.

> Problem is that nobody seems to _want_ to understand
> electronics any
> more (and this worries me a lot!).

I don't think there was ever a Golden Age when everyone
wanted to understand X (substitute any reasonably technical
subject for X). This doesn't worry me: we don't need
that many people to take an interest. Just enough so that
there are local resources available to help and encourage.

> OK, let's see how you'd get on doing jobs like

I have no experience of any of those jobs, so I would
get on quite badly. I'd hope to have a go though, and
if all I'm doing is building a replacement part, all I
would need to believe (for an item of historical interest -
basically anything old :-)) with some reasonable confidence
is that my replacement part not cause any harm to the
original components. When it comes to (for example)
bushing a plate hole on an original part, I would certainly
want to have practiced on some non-historical parts first!

> And so on. There are simple clock repairs, there are
> difficult ones. Much
> like computer repairs.


OTOH, how many old clocks are truly impossible to
repair? How many of them were constructed in such a manner
that they could not be dismantled to determine how it
was meant to work in the first place? (And for those
with bigger budgets, how impossible does the repair
remain when you can push the clock through an
appropriate MRI scanner).

With computers there are many parts whose internal
function would be very difficult to determine without
a datasheet. (And, obviously, PALs, [E]PROMs etc.
make things even harder).

None of this makes computers impossible to fix, but
it does look to be harder (and I say that as someone
who would have far more confidence in his abilities
to fix electronics than something fine and mechanical).

> Depends on the machine, of course. And as I've said many
> times, the time
> to start thinking about repairs is when the machine is still
> operational.

This is certainly true.

> That's when you pull all the PALs and ROMs and dump them (even
> copy-protected PALs can be reverse-engineered, FPGAs are almost
> impossible, though!). If a data sheet once existed (i.e. it's
> not a true
> custom part) then it's likely _somebody_ still has it...

I know that most of the datasheets for high-end parts that
I've seen at work lately (say since 2000) have been made
available through an NDA. That's fair enough at the start
(since being on the cutting edge means using the latest
parts and noone wants the competition to know what they
are doing) but with the shorter component lifetimes,
I'm not sure that these parts ever come out of the NDA
process. Getting these datasheets won't be impossible,
but it will be harder than finding data on a BC108 or
an NE555 fifty years from now!

> I couldn't do it, but I don't think it's impossible!

There are factories still churning out valves, so
it is certainly possible. There are university labs
that let you build your own transistors. These things
will hopefully eventually filter down to the hobbyist
on the street (if we're lucky). Still harder to do at
home at the moment than, say, grinding a crankshaft
or resleeving a cylinder. And more expensive to have
it done as a one-off special than it would be to
find a machine shop to do a special part for you.


Antonio Carlini arcarlini_at_iee.org
Received on Sat Sep 11 2004 - 08:50:23 BST

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