January 2016 VCFed Workshop

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January 2016 VCFed Workshop	by Bill Degnan - 02/02/2016 10:58
A typical workshop workstation complete with Red Bull and pizza boxes in the background. This set up was used to test, diagnose, and repair Commodore 1541 disk drives. I volunteered to lend a hand to restore a large collection of unknown-status drives owned by the "Vintage Computer Federation." click image for larger view. Saturday: The computer club I helped establish in 2005, formerly known as MARCH, has now become the Vintage Computer Federation, a non-profit 501C, etc. VCFed has adopted my workshops concept and now includes them as a regular feature in their event calendar. I must admit it's easier than having everyone over at my house...so long live the VCFed! In addition to a large number of 1541 drives owned by VCFed, club member Dave Gess. worked on the club's DEC PDP-8. Video of PDP-8 http://www.vintagecomput...org/evan/pdp8lights.mp4 Herb Johnson brought his PDP 8a and Dave Gessw. brought one too. Herb used Dave's complete unit to compare and contrast with his, and to help diagnose issues. Here is his write-up: http://www.retrotechnolo...store/8a_fix_jan16.html Chris F bought a TI 99/4a from me that I delivered to him on Saturday. Chris and sons worked to adapt that to his expansion "PB" unit. Ian P assisted with diagnosing and repairing the built-in drive in the TI PB1200 expansion unit. Alex worked on something over there in the corner near Jeff Gallant who had a nice "..open S-100 breadboard with an IMSAI front panel and a modern 8080 CPU card.." system. Corey Cohen and Jeff Jonas (with others?) was there helping Evan move boxes from the old exhibit room to the new exhibit space, or something to that effect. Jeff Brace ran the event and he was in particular involved in all of the 1541 repairs. Dean N, Doug C and Steve T went through 1541 drives as well as I. Hope I did not forget anyone but we put yellow stickers on the working drives, and it appears we were able to locate or revive a large number of drives for future use in the club. For me the highlight of the event was a tutoring session on how AC to DC conversion in display power supply boards works, given to me by Ian P. He had a VT52 and explained how the diodes are used to convert AC to DC and how transformers work. Helps when you are diagnosing a circuit. I usually start my analysis once the DC is established from the power supply, now I can push back to the wall outlet with more understanding. Here is a video about bridge rectifiers, (a 4 diode array) and how to convert AC to DC https://www.youtube.com/watch?v=cyhzpFqXwdA Reply