IBM 1401 Restoration Project
Meeting #7, June 30, 2004
Summary by R. Garner
Dave Bennet suggested we also contact the other known active IBM Quarter Century Clubs (Boulder and Tucson); contact IBM Fellow Ric Bradshaw in Tucson, and Jim Wiedenhammer (worked on 729 vacuum system); & contact Henry Harvel, parts distribution (in Mechanicsburg, NY?)
(A) There is a proposal that the 1401/2/3 & single 729 on display in the Museum’s visible storage (VS) might be in better physical condition and thus a better machine for restoration (assuming we get the Museum’s permission!). However, on closer examination (at 6/23 unit lead meeting), it was noted that the VS 1401 CPU backplane wiring is brimming with "red" wires, which, according to Frank, indicates significant field alterations. Also, the VS 1401 CPU’s cables are all cut off at entry to the frame and its front panel was monkey’d with. We’re also not certain we have its schematics and documentation. So the general consensus is to stick with the German 1401 CPU for restoration. However, the VS 1402 card reader/punch (esp. card handling path) and 1403 printer (esp. cover and panel indicators) are physically cleaner and less rusty and moldy than the German 1402/3 (and are 60 Hz).
One major roadblock to the idea of using the VS 1402/3 is whether it is technically possible to mix the VS 1402/3 with the German 1401 due to different supported features (729 model "intermix" feature in German 1401, "early read" feature & different visible logics in German 1402, Ramac interface in VS 1401, etc.) Second problem is that VS 1401 serial number is #20,597, which, according to Paul Pierce, is before major logic and signal changes at serial #25,000. Our German machine is serial #28,421, after the major changes. This implies the VS 1402/3 is incompatible with our more recent German 1401 CPU.
(B) Another option to address the power issue is to swap the 60-Hz ferro-resonate power supplies in the VS 1401/2 with those in our 50-Hz German machine. (Assuming we can secure the Museum’s permission!) This assumes the ferro-resonate power supply connector pin outs and voltages are the same (which may not be because of the changes after serial #25,000). This should allow us to run the 1401/2/3/6 complex at 60 Hz.
There is some indication that the 729 tape drives could be successfully run at 60 Hz. The 729’s synchronous and induction motors should operate OK at 60 Hz and the different speed of the reel motors should not be an issue with the vacuum-column based controls.
(C) Another option is to run the 1401/2/3/6 complex at 50 Hz from a converter and the 729 tape drives at 60 Hz. If the 729’s can be operated at 60 Hz, one could procure a 5-kVA static converter for just the 1401/2/3/6 complex. (Assuming there is no AC power from the 1402 to the 729’s.). This option is most straightforward, as we would not need to touch the units in visible storage, and the cost is reasonable (~$5K for new static converter.) To meet electrical code, we would need to have a single on/off switch for entire system (50 and 60 Hz.). Note that the 729’s are listed at 1.6 kVA each.
please email them to Ed Thelen.