The paragraphs below refer to photos that can be found here.)
Straight off the storage shelf, complete with dust. (After a decade it doesn't get any thicker.) We didn't use 3-wire grounding plugs in those days — nobody expected to live forever!
The incandescent lamp (remember them?) row drivers and column drivers used individually packaged bipolar transistors (remember them?).
The incandescent lamp (remember them?) row drivers and column drivers used individually packaged bipolar transistors (remember them?).
Discrete components and ICs are mounted on a thru-hole PC board and wired together with solid-conductor telephone cable wire and hippie-necklace ribbon cable. The cylindrical switches also came from computer consoles.
This side view shows the power transformer with actual wires coming out. If the picture were larger you'd see that some of the the thru-hole ICs have no numbers. Purchased as random surplus, their functions were deduced by connecting power to the pins and looking at the outputs. Many had one bad section, which meant they also had at least one good section.
New, known-good ICs were expensive!
New, known-good ICs were expensive!
The capacitors had leads, too. Switching power supplies were rare then; linear (and heavy) was the way to go. This one had a full wave rectifier.
The PC board wasn't commercially made. As I recall, I borrowed some taped artwork and made single-sided boards myself. I had no way to plate them, so I left them as bare copper. I think I may have sprayed them with Krylon Clear after construction. This one seems to be in much better shape than it could be without some sort of coating. Note the hand-wiring of the lamp matrix.
The mechanical construction was basically Plexiglas sheets and methyl methacrylate monomer.
Remarkably, it seems to work after 40 years in storage!
Which lights are on and off are determined by a shift register with feedback, which produces pseudorandom data. When a row and a column are both on, the lamp at the intersection is also turned on.
Remarkably, it seems to work after 40 years in storage!
Which lights are on and off are determined by a shift register with feedback, which produces pseudorandom data. When a row and a column are both on, the lamp at the intersection is also turned on.
No comments:
Post a Comment