1 Apr
2002
1 Apr
'02
4:49 p.m.
Well, it is harder to do, and more expensive, but I
personally find it more rewarding to hunt down old
parts and have those parts period-authentic. For
example, the Motorola 6800 I'm building uses a
Motorola 6820 (surprisingly hard to find compared to a
6821) and an MC6871 hybrid clock generator in a can,
also period and very hard to find (even the SWTPC used
its cheaper 6875 successor and a separate crystal). I
like to use ceramic/gold chips be the original maker
of the chip for machines I'll display. I suppose, if
all I wanted to do was "run" these machines, I could
just load an emulator and be done with it. Weird,
perhaps - maybe its because I couldn't afford even the
parts to build these when I was in high school(and
would be less likely to succeed in making them work or
programming them).
--- Richard Erlacher <edick(a)idcomm.com> wrote:
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What I've encountered more and more is the
inconvenience associated with
trying to use current-generation components in
wire-wrap. I'm always having
to build adapters that make a DIP out of a TSSOP or
the like. The adapters in
a prototype often exceed the cost of a PCB. It's
much easier to build small
boards, about the size of a typical playing card,
and that's enough space to
house a microcomputer of reasonable capability,
comparable with any "classic"
8-bitter of the '70's and '80's, including its I/O,
memory, video, and mass
storage interfaces. After I get the current task
off the table, I'll take a
closer look, but it seems to me that it's easier to
put a system on a
playing-card sized board, and cheaper too, using
current technology, than to
recreate the old stuff using parts that are
increasingly scarce and boards
that are needlessly large and costly.
Dick
----- Original Message -----
From: "Ethan Dicks" <erd_6502(a)yahoo.com>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, April 01, 2002 3:35 PM
Subject: PCB vs perfboard construction economics
(was Re: "New" PDP-8)
http://penguincentral.com/retrocomputing/retrogaming/
--- Ben Franchuk <bfranchuk(a)jetnet.ab.ca>
wrote:
> ...The board will be about 8" x 7" and $175
canadian for two
> prototype boards. Wire wrap
sockets/wire/protoboard would cost me $100...
While I can recommend a real PCB if the setup
costs and the per-sq-in
costs are not killing you (price an Omnibus or
Unibus-sized 4-layer board,
complete with gold fingers!), personally, my WW
overhead isn't terrible:
I rescued all the prototype hardware from my
former employer when they
went bust - I probably have three lifetimes worth
of WW sockets. When
I do a project, the only part I have to spend
money on is the wire.
My last project is a good case-study for expense
vs. time. I wanted to
replicate a scoreboard from a Dragon's
Lair/Space
Ace. I tried to find
one on ePay, but they only come up occasionally
(every couple of months).
I decided to build one. I started with a couple
of digital pictures,
a parts list and a schematic. Since the board
was
approx 6"x9", it
would have been somewhat expensive for a
commercially-made PCB. There
are still plenty of surplus units out there that
sell used for under $50
when they are available, so it would be cheaper
to
wait for a sale than
to have a professional PCB created unless the new
PCB added value somehow.
I had the blue perfboard (from when the
MicroCenter got rid of all of their
prototyping hardware at 80% off list!), the wire
and the discrete
components. I had to purchase the LEDs ($0.65
each) and the driver chips
(a few bucks each). Total out-of-pocket expense
was <$25. I probably
pulled about $15-$20-worth of supplies out of my
parts bins.
Construction took place over several evenings,
watching the sci-fi channel,
tacking down point-to-point connections
(didn't
have the vertical
clearance for socketing the LEDs). I'm
pleased
that it worked the first
time! - pictures at
under the
"LED Scoreboard" link. Mostly, it's
pictures of the glow of
the LEDs, but there's one out-of-focus,
flash-burned picture of the
perfboard and yellow wire in there (the Apple
QT150 has about a 24" min
focal distance without the strap-on lens).
The upshot was that if this were being done for
anyone but me personally,
it would have been an economic disaster. Nobody
would have paid me a
reasonable amount for that much work - it would
have been much cheaper
to go to an arcade service company and *buy* a
used scoreboard than spend
10+ hours wiring up a board. It would have been
much cheaper than that
to wait out the next wave of offerings on eBay
(which I accidentally did -
the project took so long to complete that I _did_
pick a real one up for
around $30, after I was 95% finished with my
replica. The good news is
that it made a nice functional benchmark to prove
that mine worked).
So I chose to trade my time for semi-instant
gratification. I would
have loved to have done a PCB, but I chose not to
spend the time with
layout tape and a blank board, and I chose not to
pay to register a
demo-ware layout package so I could make a
6"x9"
board. If I were to
make the new PDP-8 design that kicked off this
whole thread, I'm not
sure if I'd get professional boards
(~$200/set, in
small quantities,
according to the designer, for a couple of
4-layer
boards) or I'd
point-to-point it. In terms of $$$/hour, even
$200 for a board set
is cheap. In terms of a discretionary hobby,
$200
is a lot to divert
from other projects when I already _have_ a
working PDP-8. With that
kind of money, I could start trolling for a Qbus
SCSI controller!
Back to the initial topic, though, I'd love to get
a good buy on a dozen or
so spools of kynar-coated wire. I'd prefer
an
assortment of colors, but
I'd take it in whatever I could get - yellow,
red,
white...
Anyone have a lead on any surplus places that have
it for a few bucks
a spool?
-ethan
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