Log of January 2007 events
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Tuesday, January 23,
Tuesday, January 23
These are notes of the RAMAC Tuesday January 23rd meeting -
Next meeting February 6th.
Present were Al Hoagland, Dave Bennet, Dick Oswald, Ed Thelen.
Looking about, and checking the e-mail, Dave Bennet discovered that he had forgotten to invite Joe Feng (who has completed reading and capturing the existing data on "our" RAMAC). Dave called Joe and apologized - Dave did not grovel as I suggested ;-))
Track Position Pot
Apparently the possible good one is in storage and inaccessible. John Best is trying to move things along so that Dave Bennet can measure its electrical characteristics (and see if any taps are open).
Dave Bennet reports that the larger starting capacitor for the electric motor causes successful motor starting :-)) Grant Saviers had suggested getting one of about double capacity, the one that now works is 550 UFD. Unfortunately, the compressor is leaking oil, Dave Bennet will cut and install a new gasket.
Dick Oswald has made all schematics and purchased most electronic components. The current exercise to remove lead from electronic parts ("Green") has most manufacturers stopping manufacture of "dip" packages so dear to us of the 1970s and 80s. Packages being produced are mostly surface mount - a big pain for amateurs.
Dick Oswald (left) and Dave Bennet talking schematics
Disk Select interface
Track Select interface
Dick is proposing building into chassis mountable in industry standard 19 inch racks. He liked the packaging ideas shown in the 1401 TAU electronics chassis. He proposes placing each function on a separate 3.3x4.5 inch perforated boards on 0.1 inch centers. Dick is open to ideas.
Dick likes to use #30 Teflon covered solid wire for solder connections. Amateur wirewrap has a poor reliability history. He probably has enough for this project, but if you know of more - please advise -
Ribbon connection with plugs on 0.1 inch centers seems fine.
"We" would like some packaging advice. I promised to get Dick connected with Bob Feretich and Grant Saviers who were involved with the very professional looking 1401 "TAU Box".
Dick is planing to use a cubic polynomial taper function on the servo control. This should enhance the normal servo based on position error and velocity feedback. Dick REALLY wants the RAMAC to meet seek time seek time specifications.
We discussed machine protection. Dick says that if a seek is not completed in one second, power circuits will open to prevent clutch over heating and some other potential problems.
Ya know, that Dick Oswald is one foxy feller. I (Ed Thelen) have had just enough circuit experience to recognize that Dick is a superb circuit artist (engineering is an art as well as science). He and Steve Wozniak should compare notes. It is a joy and inspiration to view his work.
The Search for the RAMAC plug at Santa Clara - background task
Al Hoagland and Dave Bennet are trying to find an original plug containing coax connectors removed from the RAMAC at Santa Clara University. The plug was replaced because no mate could be found for it. In the interests of "reversibility", we would like to have the original. - Something about Dave going to "Yurba Buena" to photograph one there to provide information. -
Questions to ask of the Germans at Sindelfingen about their RAMAC - background task
Al Hoagland had made a list of questions to ask of the Sindelfingen group. A trip by Van Snyder did not materialize, and the list is apparently near the bottom of (my?) stack. (Al remembers to-do lists too good!!)
We got into a fun discussion of early drums - Al Hoagland later provided this clarification:
"The first approach to a magnetic drum was to wrap the surface with a long strip of magnetic tape in the form of a helix. This would give some indication of signals and write currents under the unique conditions a drum had (as compared to a tape drive) of a non-contact spacing and very high surface speed. The main approaches to a suitable design were creating a metal surface by wrapping cunife wire and machining (IBM) as well as plating. The main approach for an oxide coated drum was spray painting. For the RAMAC disk the technique latter moved to spin coating."