24 Aug
2001
24 Aug
'01
3:48 a.m.
At 10:57 pm 23/08/2001 +0100, you wrote:
Something which (as you'll come to discover if you hang around on
classiccmp) I don't care much about. It is certainly well down with
respect to functionality.
That's fair enough. Personally, I doubt any of the older computers are
*truly* elegant internally - there was too much learning going on. I'm not
even sure if it's true of modern computers either.
Of course, you'll prove me wrong now... ;)
Well, just about every other plastic-cased PET owner I know thinks that
'SK' stands for 'Stupid Kludge' :-)
Heh. Speaking of kludges, I've got a WordCraft dongle (but no WordCraft) if
anyone has lost theirs.
So? The thing has a GPIB interface, so it's reasonable to assume it's
going to be possibly used to control test equipment. Making it just to
wide to sit on a shelf in a rack is very annoying. It's just another
aspect of the bad design of this case...
Were Commodore really thinking that? I know the HP stuff was suited to
controlling 'scopes and the like through the 488 bus, but I don't recall
them having external drives, printers, etc. controlled via it. ICBW...
Agreed.
Yup, one of the cbm-hackers guys kindly provided a set of instructions on
how to remove the mainboard with minimum disruption; useful as it means I
can get to the voltage regulators and check them (they're fine).
Indeed. The secondary cassette port is in a different place, and the
monitor signal connector has moved as well.
Well, true.... Are GPIB connectors still reasonably available? I ask
because the ones which came with the machine (& the cable) have sustained
some connector damage at some point; they work, but I have to be *really*
careful connecting them up.
No, there's just a bunch of signal wires which drop down onto the main
board, and two AC lines which mosey up on into the monitor cabinet (which,
awkwardly, are soldered directly to the PSU).
:) I have used 'scopes in the past, I guess it's just a case of remembering
how. And maybe (shock, horror) reading the instructions.
Exactly. Watching an expert at work is very educational, but nothing like
rolling the sleeves up and getting in there oneself. And, with the combined
skill of this maillist, if I *do* get stuck, I know where to turn for
assistance.
Erm, it *is* brown - but a nice factory brown, and it's not slightly
crumbly or showing any signs of discolouration...
ESR?
For now, I don't see myself working with the latest & greatest; I've only
got one duff PET at the moment, although if I can get this one running
again, I may more actively seek broken kit, if only for practice.
However, whilst I like the idea of learning embedded systems, I'll probably
start simple and use a Z80 or similar - I can't (yet) think of anything
where I'd use some super-fast chip. Incidentally, what's with these PIC
chips? They seem to be very popular at the moment.
I tend to agree. I could use a parallel-port device relatively easily (I
have a couple of laptops), but space is of a sufficent premium here that it
would genuinely be easier to have a self-contained device.
Cheers!
Ade.
--
B-Racing: B where it's at :-)
http://www.b-racing.co.uk
Actually, I think it's a stupid design.
Erm, I was thinking more of the way it looks on the desk... The 'separate keyboard' seems
nice until you move it away from the machine, whereupon the keyboard
cable unplugs itself from the DB25 on the main unit.
I never found that to be a problem, although I mostly used it with the keyboard in it's looks-like-its-attached
position; It would probably have
been better with an IDC connector (ala the Osbourne).
Or with locking screws on the DB25...
The thing is just
too wide to fit on a shelf in a 19" rack.
They're supposed to sit on desks, not racks... Internally it's a mess. The PSU is in a crazy
position; the 240V supply
Agreed. It's really a normal 8032 re-cased, and it doesn't really fit the
new case... The 8296 (same case, totally revised mainboard) is a
lot
better in this respect I believe.
I've not seen one of those; I did wonder if the expansion board I've got in
my 8032 (which turns it into an 8096) would fit, but I don't think there's
enough height in the -SK case.
line is too
short and stretches dangerously if the unit is opened to
90degrees, the balance is all wrong, and yes - it's just an 8032 board
I seem to remember it's best to take the monitor off first (Rotate it to
free the tilt/swivel base, then unplug the 9 pin mate-n-lock connector).
Then the case opens without straining too much of the wiring, and without
the darn machine falling over all the time. rotated (although there are subtle differences
between the -SK board and
the regular board, although that may just be down to different revisions
I think it's just different revisions. There's no reason for any
electrical changes to the board. between the machines. The only reason it
doesn't need a "special"
PET-->IEEE cable is because it already has one internally... Useful,
Sure....
because I've plundered it to test the
diskdrives I've now got with the
regular 8032 (and they work nicely!). Shame they didn't bother to put the
plastic keys in, so there's the possibility of putting it on upside down -
Yes, but the average user is not expected to ever unplug the edge
connectors inside the 8032.... luckily that
didn't happen to me. Oh yes, the monitor signal & power cables
go through a connector which floats in the middle of the machine - it looks
like someone forgot about that until the last second...
Indeed. I can't remember if the normal 8032 has that or not. The 8296
certainly does.... It's useful in that you can remove the monitor easily,
and the rest of the machine (PSU + logic board) is then a lot easier to
work on...
With the old 8032, I find a suitably calibrated pile of books behind the
machine can be used to rest the back of the monitor, so you can open the
case to the extent of the hinge. I used a similar trick with the 8032SK...
I think simple, but reasonably useful for now at
least; I may need fancy
stuff in the future, but I'd prefer a "beginners" instrument for now.
I'll
I would not class the 465 (or any Tektronix 'scope) as a 'beginner's
instrument' :-). Yes, they can be simple to use, but they have enough
facilities to keep you going for a long time. You are not going to
outgrow it anytime soon. There are things it won't do, but you rarely want
to do them anyway (how
often do you need an RF spectrum analyser for computer repair, for example
:-)). For displaying waveforms it'll do all you (or I) am likely to need.
Indeed...
Suffice it to say that a valved 'scope can still be
a very useful
instrument (I'd much rather have a good valved 'scope than a typical
hobbyist grade modern 'scope). But it is going to need a bit of looking
after. You are going to have to recalibrate it from time to time, and
rebalance the amplifiers, and so on. It's not difficult, but it may not
be the sort of thing you want to get into.
Perhaps not *just* yet; I'm sure that the desire will come with time...
Agreed. If I
don't get the basics learned first, I'd just end up a spare
wheel...
Yes. While I'm sure I could fix this PET (and I could even explain what
I'd done), you'll learn a lot more by doing it yourself. I'll check that. I had to remove the whole
gubbins from my working 8032
when the mains filter exploded, but I didn't check any resistances/voltages
there. All the connections have been un-made then re-made, so if the HR
usually comes from mucky connectors, that's unlikely. If the cap is going,
Normally, if the PSU connector goes high resistance, it overheats and the
plastic turns brown. It's easy to spot... however, moving it around would have no effect.
Is there any way to test for a drying cap?
YEs, you need an ESR meter (or a good impedance bridge). The former is not too expensive (around 50 quid, especially if you
buy it as a kit),
and is probably worth getting if you get seriously into doing repairs
(particularly of switch-mode PSUs). The latter is expensive, and is only
worth getting you do a lot of design (or research :-)), or if somebody
gives you a broken one (as happened to me...)
:) I shall live in hope...
[Stewarts]
I've actually had a couple of offers of 'scopes (thanks, chaps), so I shall
see what becomes of those first.
No harm in asking... I may drive out on Saturday
and have a look, if
they're open.
I can't remember if they open Saturday mornings. I am pretty sure they
close in the afternoon.
[Logic analysers]
> GBP500 is reasonable,
(actually, this referred to *all* test kit, not just an LA)
I'd say, so
long as the kit is going to last a while
and do most of the stuff I need of it. I can always sell it on later, of
course, when/if I need to upgrade.
It depends on what you want to do. If you are going to work mostly on
classic stuff then a 100MHz 16 channel analyser should be enough (it'll
be useful on all 8 bit micros, PDPs (8s, 11s, 10s, etc), older VAXen, and
so on. If you are intending to do some designing with the latest chips
then you might need something faster in the end. What about one
of these software oscilloscopes? I think the only one I've
seen was a picture on EPE's website, but there must be a few of them
surely? Mind you, hardly a portable device if you need a pentium PC within
reach...
I'd not bother with them. They are not exactly convenient to use (and you
have to get a PC to put them in (or at least I would...). They are
digital sampling storage scopes (which is nice), but I suspect a good old
analogue scope is more useful to you at the moment.