"New" PDP-8

From: Ethan Dicks <erd_6502_at_yahoo.com>
Date: Mon Apr 1 17:07:36 2002

--- Loboyko Steve <sloboyko_at_yahoo.com> wrote:
> ...A drag about the DECmate board was that its a multilayer
> board, and in spite of my best desoldering efforts,
> the chips are trimmed short and you can't really use
> many parts from it other than the socketed BTS6120 and
> a few EPROMS.

What else would be "useful" from a DECmate board? I agree about
the difficulty of removing chips from multi-layer boards. Depending
on the exact nature of the power/ground pins/planes, it can take
a lot of heat to remove the chips. Usually, you pick either the
chip or the board as what you want to survive and you sacrifice
one for the other (it's possible to do both, but it's a *lot* more
work, and sometimes you still ruin one or the other or both).

I recently pulled a custom 20-pin DEC chip from a DWBUA to install
in another DWBUA in an attempt to get one working board. First, I
had to remove the dead chip from the recipient board - that took 30
minutes to get the power/ground pins out and the thru-holes clean;
then I had to remove the chip from the other board without destroying
the chip - another 30 minutes. It's easier with the "right" tools...
all I had was a Weller temp-controlled soldering station, solder,
solder wick and a solder sucker. With about a $500 desoldering station,
it probably would have taken under 10 minutes.

But, again, I'm curious what you would save from the DM board if you
could. Personally, if I ever build Bob's design, I'll probably
crack open a DM (I have one I, one II and one III) and borrow the
CPU chip. EPROMs I have aplenty, as well as PALs, GALs and TTL
"popcorn" parts. I can't imagine what I'd want to pull from the
donor system except for the CPU chip itself. That way, I could put
it back anytime I wished.


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Received on Mon Apr 01 2002 - 17:07:36 BST

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