Re: The best CP/M emulator
((yeah yeah I know... this one's pretty stale .... tough choice
send it or hit the delete key ... oh well ... for the 'record'....)
On Sun, 29 May 2005 15:47:36 -0700, "Jack Pea****"
>"Dave Griffith" <firstname.lastname@example.org> wrote in message
>> I shudder to think what PCB design would be like without graphics.
>Light board, xacto knife, clear plastic film and lots of black tape. Where
>do you think the term "rip and replace" came from? Layout was usually done
>in 2x, then reduced on a camera. If you were good at it you could coat your
>own blank boards with photoresist,[/color]
Can you still buy fresh tape and pads?
I had a newspaper just down the block, so getting reductions on their
process camera was easy. After a while I just taped 1:1 and did away
with the reduction step.
I had a good piece of luck in the Univac surplus pile - found three
small ChemCut etchers - sold two to get mine more or less free.
Really did a nice job using ammonium persulphate. You had to heat
it to around 130 degrees before starting, but then the reaction was
exothermic, so you might have to cool it if you were removing a lot of
copper. A lot safer and cleaner than ferric chloride. What you ended
up with as exhausted solution was copper sulphate, used to control
weeds in ponds and lakes. Unless you were also using a mercuric
compound as a catalyst to speed things up. Biohazardous, that.
The spray only hit the bottom side of the board, so you had to turn it
over for double-sided. Model 600, I think they were. And a Pexto floor
shear to cut the boards apart. And high speed carbide drills.
Because of the heat, I usually baked the photoresist after developing
so it wouldn't break down in the etcher. Also, did some silk screening
of resist - not as fine as photo-resist but a whole lot quicker when
there were a bunch of boards to do. Oh, almost forgot - NuArc plate
maker allowed a lot of photo process things - artwork, resist masks,
metal foil labels (isn't the Altair logo one?) etc. And then, 3-M
Color key. Neat stuff.
Ammonium persulphate also could do a good job etching brass.
Ah, the good old days.