It's like Rob Ross for nerds

Expect to lose an hour of your life, but learn some things along the way.

https://www.youtube.com/watch?v=l7rce6IQDWs
then
https://www.youtube.com/watch?v=uqY3FMuMuRo
then
https://www.youtube.com/watch?v=BUTHtNrpwiI

At first glance I was expecting to see an array of resistors as part of a D-to-A but that’s not in the schematics¹ so without checking chip part numbers I guess he’s shortcut a little.

¹ There’s a link in part 2

He has, but it only outputs four levels on three channels (for 64 colours) so he’s done that with six resistors. Ingenious!

He has, but it only outputs four levels on three channels (for 64 colours) so he’s done that with six resistors. Ingenious!

Saw the 6 resistor bit and thought “not enough for the proper colour range”
This one eye stuff (or age) is slowing me down, I used to “read” circuit diagrams.

I used to “read” circuit diagrams

I used to write them… http://clive.semmens.org.uk/Art/TechDrawings.html …those were the days, hand drawn circuit diagrams, & tape & transfers on film for circuit boards…even for some fairly major companies…

Did you ever do a write-up of how you did a conversation from circuit diagram to board?

Did you see the circuit board pointed to by Rick? Ref stardot

hand drawn circuit diagrams, & tape & transfers on film for circuit boards…

There’s a box buried in the mountain in the garage, there’s an etch resist pen in there which I’m pretty certain has dried up :)

I have none of the wonderfully harmless¹ etch solution anyway.

¹ Relative to some of the other stuff from my teens.

Did you ever do a write-up of how you did a conversation from circuit diagram to board?

No. I probably should have done. I did it by Instinct, and Application of Rules (about things like how far apart 240V mains had to be, how far they had to be from anything else, how far EHT for the CRT had to be from anything else, how to avoid cross-talk between signals with larger currents and signals with small voltages. You know the kind of thing I’m sure. Oh – and making room for the actual sizes of the components, and a little thought for the fingers of the people who would insert those components – and the order in which the components would be inserted. Of course if one of the components inserted early in the process needs changing, that’s another issue…relevantly: http://clive.semmens.org.uk/Fiction/Bullying.html (although that’s in “fiction”, it’s basically a recount with names changed and from the fictional Penny’s pov).

Did you see the circuit board pointed to by Rick? Ref stardot

Sadly, no. I was (and am) at the laptop, with internet connection too poor for video.

There’s a box buried in the mountain in the garage, there’s an etch resist pen in there which I’m pretty certain has dried up :)

Now I never did any of this stuff at home, and never used an etch resist pen. I only ever did it at client’s premises. My point was that even major companies were doing things that way at the time! Not with etch resist pens, mind. I did the circuit diagrams – that actually ended up printed in technical manuals – and made the circuit board artworks. But those artworks went off to be photographically reduced (I did them at 2x or 4x final size) and manufactured by specialist PCB manufacturers.

Some examples of things I did for Microvitec, and one other company who shall remain nameless (got swallowed up by a bigger fish I believe, but could simply have vanished. Not sure.) Got lots of other samples at son’s house, never scanned, not yet anyway. More Microvitec ones, and many for other companies too.

https://www.riscosopen.org/forum/forums/10/topics/15769?page=2#posts-108507