4 Oct
2007
4 Oct
'07
7:17 p.m.
On 04/10/2007, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
There have been reports of the accuracy -- or lack of
it -- of those
cheap meters, Many of them do odd things if the internal battery is flat
(and don't rely on the 'battery low' indicator for this), and there have
been problems due to the poor quality switches used.
A friend of mine was nearly killed due to this. He tested some wiring for
voltage-to-earth and the meter said it was essentially dead. SO he
started workign, alas the meter was malfuctioning, and he got the full
mains volatege across him. He imediately went and bought an expensive mad
reliable neter.
Oh dear. Oh very much dear.
A logic analyser is a bit lile a 'scope in that it
displays a grpah of
signals against time. The differnces are (a) it records the signals and
displays the recorded version (some 'scopes do that too -- storage
'scopes), (b) it only works with digital signals (it doesn't display the
voltage, only whether they are high or low), and (c) it has many more
input channels (even a good 'scope rarely has more than 4 channels, a
logic analyser will have 16 or more).
Fascinating. The snag is, I know very little about electronics below
the level of a broad knowledge of TTL, the rudiments of circuits and
gates and so on. I have a bit of theory, no practice. I could not
diagnose a faulty chip or anything; my troubleshooting consists of
swap bits until it works. And at this, I know more than most people I
know in the PC world; I find it amusing that I can both fix TCP/IP
problems on a corporate WAN which have baffled a room full of senior
techies and diagnose a faulty DIMM or spot an incorrect amount of
cache on a modern PC. By C21 PC tech standards, I'm an old-timer with
low-level knowledge. I have worked with hundreds of people who have
never seen an OS older than Windows XP or maybe, for the veterans,
Windows 2000, who have never seen an ISA card or a SIMM and don't know
what they are.
I am puzzled by people who want to run old hardware,
but who don't want
to learn to repair it to component level. I can understand why people
want to run the software under emulation (even if that's not what I want
to do), but I am seriously wondering what extra you get from running the
old machien _other_ than being able to fully understnad and repair the
hardware.
Notice I said 'I am puzzled' not 'you are wrong'. Perhaps somebody could
enlighten me...
Well, aside from 1 old Sun (SPARCstation IPX), the soon-to-arrive
VAXstation, an Amiga and 2 STs and a QL, all my kit is Macs and PCs.
The PCs range from a 386 to an Athlon XP, Macs from an SE/30 to a Blue
& White G3/400MHz. So I don't run what most people here would consider
"old hardware", I suppose!
I'm interested in things like the Sun and the DEC - and my couple of
IBM PS/2s and even the 9" mono compact Macs - because I hugely admire
the engineering and design of these machines from before the rise of
the mass-market PC. Things were /different/ then.
Look at a modern Acorn-compatible or Amiga-compatible and it's just
another ATX motherboard with the usual interfaces and slots. Yes, it's
a different CPU and a different OS, but it's a machine in disguise as
a PC. A sheep in wolf's clothing, sadly, these days: contemporary RISC
desktops are actually considerably /slower/ than a modern PC, even a
cheap one. This is in part compensated for by the efficiency of their
OSs.
So I appreciate the way things used to be. However, my Sun is dead
with a duff NVRAM battery, which means changing the chip, and that,
while it doesn't fill me with terror, intimidates me enough that it
went into storage in about 1998 and it's been there ever since.
I am, a bit like Chuck, mainly a software person, but one who's
competent with hardware to a basic level. I know bugger-all about
electronics and while I regret that, I'm not inclined to fix it now. I
just have an aesthetic appreciation for the way things /used/ to be
done.
I'm not sure if that answers your question, really...
And please don't throw away PCBs from vintage
machines, even if they're
defective. Somevody else might be able to repair them, or use parts off
them. For example one machine I am currently working on has a RAM board
containing 16 off Intel 1103 DRAMs. These were the first 1Kbit DRAM chip
(35+ years ago...) and are very hard to find now. If one of those chips
fails and you replace the board, the old board could supply 15 very
useful chips to somebody else.
Well, I would offer it here, but my "vintage" kit is old ISA boards,
dead MC680x0 Macs and suchlike. Probably not of much interest to
classic collectors, I fear.
--
Liam Proven ? Profile: http://www.linkedin.com/in/liamproven
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