Importance of "original" parts

From: Tony Duell <ard_at_odin.phy.bris.ac.uk>
Date: Mon Dec 8 11:53:04 1997

On Mon, 8 Dec 1997, Neil McNeight wrote:

>
> Greetings.
>
> I have recently developed an interest in collecting classic computers and
> after (mostly) lurking on this list, I have a question that you all might
> be able to answer.

OK, here's my $0.02...


>
> How important is it to obtain computers in their "original" state? Is it
> worth it to save a computer that is known to have been hacked together?

Important to _whom_? I collect computers for one reason and one reason
only - I enjoy doing so. I enjoy using them, I enjoy repairing them, and I
enjoy hacking them. I do not collect them because I have this belief that
in 20 years time I'll be able to sell them and retire on the money.

Now, I want to have working computers. That doesn't mean that I only
accept working computers, or even only complete computers. It means that I
try to repair non-working ones and make/obtain missing parts for
incomplete ones. So virtually _all_ machines in my collection are
non-original in some way.

For example, I have a DEC MINC (Modular INstrument Computer) that I've
pulled the 11/03 CPU card from. It's got one end of a DW11-B (Unibus-Qbus
interface) in place of said CPU card. The other end of the DW11-B is in my
11/45 CPU. So I now have something that DEC never built - a modular
real-time I/O system on an 11/45. Unoriginal? Sure. Interesting, and worth
doing? IMHO yes.

My IBM PC/AT has also been hacked a lot. There's 2 extra EPROMs on the
motherboard containing a patched hard disk table. And a couple of TTL
chips to enable them. The IDE card has a piece of stripboard kludged onto
it to give it a connector for an 'active' LED - something that was missed
out of the original card. The motherboard is the original IBM one, though.

IMHO a PC-class machine has to have at least the original motherboard to
be 'interesting' (mainly because I have all the IBM schematics and very
few others). But my XT's and portables all have the 640K mod done to them.

One of my classic PERQs has a QIC-02 interface wire-wrapped in spare space
on the I/O card. PERQ systems used another slot for that.

And I've not even started on repairs where I tend to use any component
that's electrically equivalent (I repair to chip level, so the issue of
unoriginal boards doesn't come up). I've used FAST TTL to fix PDP11's. The
chopper transistor in one of my VT100 PSUs is not original, and nor are
many of the components in my PERQ 1 PSU. My RK11-C has a chip sellotaped
to one of the flip-chip cards and linked up with kludge-wires. And so
on...

I guess what it comes down to is that the architecture _MUST_ be preserved
(a pentium motherboard in a DEC BA11-K is a mess!), as far as possible the
circuitry must be preserved (so that you do use electrically equivalent
components when you do repairs, and don't just swap boards), and mods to
improve functionality are fine, even if done today.

>
> For example: I have an original Mac 128k. However, I believe that the
> motherboard has been upgraded to the 512k "Fat" Mac. I purchased it at the
> University of Michigan's Property Disposal warehouse, which means I was
> lucky to find a matching keyboard and mouse and I have no hope of finding
> the original manuals or shipping boxes for it.
>
> Should I even bother to restore this machine to it's original state by
> purchasing an original (but not _the_ original) motherboard, assuming I

I'd probably look for an original motherboard, if only because it'd be
nice to have one. As to which one I kept in the machine, well, that's up
to you. But I'd certainly use the machine as it is now - what have you
got to lose?


> -Neil

-tony
Received on Mon Dec 08 1997 - 11:53:04 GMT