Component level repair (Was: Re: Setting up a VAXstation)

[Liam Proven]

On 06/10/2007, Bryan Pope <bpope at wordstock.com> wrote:
> And thusly were the wise words spake by Liam Proven
> >
> > On 05/10/2007, Bryan Pope <bpope at wordstock.com> wrote:
> > > And thusly were the wise words spake by Liam Proven
> > > >
> > > > 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
> > >
> > > All you need to start with is a logic probe.  Then for simple logic
> > > chips like AND, OR, NOT you would place the logic probe on the one
> > > or two inputs o see if they are high or low.  Then from that you
> > > would know what the output should be.  For chips that were a little
> > > more complex you would use the truth table from the datasheet for
> > > the particular chip to see what the output should be for each
> > > combination of input(s).
> >
> > Er, hardly, when a modern chip has several tens of millions of gates on it!
> >
> > I make my meagre crust working on machines of, on average, 2-3GHz of
> > processing power, 1-2 gig of RAM and about a quarter to a half a
> > terabyte of RAM. I fear when one of those goes wrong, probing for a
> > duff transistor will do me little good!
>
> Errgh..  I was *not* talking about anything modern!! :( :(  Is not
> this a *vintage* computer email group?!  I was referring to things
> like C= PETs, 4040s and other systems from that era!  ie stuff you
> can test with equipment that does not mortgage your house..

But I don't and wouldn't even /attempt/ to fix anything that old. I
have a couple of vintage machines, and I'd like to keep them running,
but personally, that's more or less enough for me.

I read with great fascination the discussions in this group, but for
me, getting my first computer in 1982 or '83, I'm not really
interested in owning anything before the early-1980s 8-bit home
micros. And since there were many dozens of makes and I have
absolutely no use for any of them, I confine myself to the few I still
have. In the later '80s, there were a much smaller number of much more
powerful 16- (or 32-) bit machines. I've got one of each of the big
ones: a QL, an Amiga, an ST and several Acorns - an Archimedes and an
A5000 and a RISC-PC.

Apart from that, it's all Macs and PCs.

That suits me fine. They were all free or /extremely/ cheap. If one
dies, I'll try to find someone who wants it & I'll get another one.

Things like logic analysers would be of little to no use to me on the
machines I work with, which contain no discrete logic at all, just a
few SMT or BGA VLSI ICs. They are, for the most part, impossible for
human hands to repair, and if they were, it wouldn't be economical.
So, I don't.

I'd vaguely like to know how to run a metal smelter, how to forge and
cast metal, how to do carpentry and whatnot, but they're archaic
skills of no actual /use/ to me. I'm afraid tracing a duff RAM chip or
replacing a serial line driver is in the same bucket in 2007.

> > > I know for the Amiga Commodore provided schematics...
> >
> > I know a few dozen characters of Chinese. I also know that I could buy
> > a Chinese dictionary, but it wouldn't tell me anything! :¬)
>
> But the schematics can help you fix a problem..  Even if you are only
> following the connections, it may help to show you which component
> failed by what the problem is and what is still working.

How? Given I have no analysers and wouldn't know how to use one if I did?

The Amiga cost me a copy of NT4 and a Compaq server Ethernet card. Its
accelerator and Squirrel SCSI cost me £25 together. Hard disk, RAM,
cables and software were all free. If any of it dies, I'll scrounge
other bits.

As an operating system aficionado, I want to know a bit about AmigaOS
works, as it's widely held as a classic design. I've no desire and no
need to know how to fix a duff Amiga, though.

> So now you will be able to write a TCP/IP stack for a vintage computer? ;)

No. Why would I want to? I'm not a programmer. I can program but I'm
/rotten/ at it.

> How computers work is pretty much the same since the beginning.. they
> have just got faster over time. (and a lot more sterile, IMHO)

I'd have to agree, yes. But learning to service a Model T - or, given
my personal predilections as a biker, a Rudge or Douglas or AJS -
would not be much help in running my ZZR1100. The owner's manual says,
pretty much, check oil, chain tension, brakes and lights; otherwise,
take it to the dealer. That's what I do.

If I repair my PC badly, I might lose some data. If I repair my bike
badly, I might die. I already have a metal arm, a metal leg and badly
damaged inner ears from a severe bike crash. I don't want another. I
leave it to the pros.

-- 
Liam Proven • Profile: http://www.linkedin.com/in/liamproven
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