Design007 Magazine

Design007-June2021

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JUNE 2021 I DESIGN007 MAGAZINE 17 is new DEC computer featured printed cir- cuits that were all single-sided or double-sided, non-plated through-holes (Figure 3). I did not know anything about PCBs at the time, so I fol- lowed the computer science department and used their tin-lead plated, NPTH breadboards to wire up my new computer interfaces with com- ponent drivers (Figure 4). Sockets were used for the integrated circuits and the wiring was done with solid tinned-copper wire insulated with PTFE tubing (Figure 5). No one said a thing about the connector fingers being tin-lead, and that if plugged into gold bifurcated connectors, a galvanic corrosion would be set up. So, it was a common practice to remove all the PCBs and vigorously "erase" the fingers with a pink gum eraser to remove the corro- sion products. is was especially important as the students' rats were housed in the closet near the computer and you could always detect the faint smell of urine in the air. Later, aer joining HP, I learned about printed circuit fabrication and designed the artwork for new interface cards. I had them made as PTHs in our Palo Alto, Calif., PCB facility and assembled with proper wave sol- dering. I sent these back to the psychology department and instructed them to remove my old hand-wired boards and use these proper boards instead. Years later, friends tell me the old blood stor- age Skinner boxes and PDP 8/L computer are still there working fine. I wonder if they updated any of my programs? It's been a long time since Star Trek debuted, but I expect technology to continue to go where no designer has gone before. DESIGN007 Happy Holden has worked in printed circuit technology since 1970 with Hewlett-Packard, NanYa/Westwood, Merix, Foxconn and Gentex. He is currently a contributing technical editor with I-Connect007. Video 2: The DEC PDP 8/L. Click here to view video.

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