IBM 1401 Restoration Project Report

by Robert Garner
January 16, 2005

Here's the new, (short ;-) high-level monthly status report on our 1401 restoration project. All errors/omissions here are my own!

Status:

• General/Team:
  About ten volunteers (mostly retired IBM Customer Engineers) regularly attend the restoration sessions every Weds and 2nd/4th Saturdays. The documentation and schematics that accompanied the 1401 have been mostly copied and are now in regular use.

• Power:
  In December, after 3-phase wall circuit breakers were upgraded to 60A per phase, the 50-Hz power generation stabilized. However, there is only power enough (4 kVA) to operate electronics or AC motors, but not both simultaneously. Electronic debugging and motor checking can go in parallel, but within a month or so we'll require our full power conversion solution. In general, issues with 50-Hz power generation has slowed progress.

• 1401 CPU:
  Ron & Bob are debugging the CPU electronics. A couple of faulty SMS circuit cards were identified in the clock generation logic, which is now cleanly producing all internal clocks. There are a couple of stuck bits in the core memory addressing logic. Faulty front panel bulbs were replaced.

• 1402 Card Reader/Punch:
  Bill & Don completed the pre-approved swapping of several mechanical subassemblies from the Visible Storage 1402. The 1402 card path was manually turned.

• 1403 Printer:
  Frank cleaned, lubricated, and operated the mechanical paths, belts, and motors. The 1403 is in good shape, substantially ready to print.

• 729 Tape:
  Allen is initially focusing on two of the five drives (Model V's), which have been throughly cleaned and inspected. Several small mechanical repairs and item reproductions were performed by a machinist at the IBM Almaden Research facility. New belts were located at a San Jose supplier.

• Software:
  Ron Mak's software group has been quite active with email on the new "1401_software" list. To help re-learn the instruction set, two numerical programs, "500 digits of pi" and "1000 digits of sqrt(2)" were written, debugged, and fine tuned on simulators. The three existing 1401 simulators on the web were evaluated and critiqued. Van Synder's Autocoder assembler (written in Fortran 90) was ported to MS DOS. About a quarter of the 1401 punched cards were read into about 54 (card set) files using the Museum's card reader.

Plans:

• General/Team:
  Next all-hands meeting will be scheduled in about a month.

• Power:
  Procure an 18 kVA or greater power converter. Within a week or so, the CHM should have an opportunity to bid on a used, 36-kVA static power converter. This unit will more than meet our total 50-Hz power needs (about 13 kVA static).

• 1401 CPU:
  Focus will be on debugging the electronics, including the stuck memory address bits and confirming the integrity of core memory. Diagnostic instruction sequences will be manually entered and verified.

• 1402 Card Reader/Punch:
  The motor will be tested and the read/punch path cleaned, lubricated, and re-timed. The VS 1402 door repairs will be finished and the unit moved back into Visible Storage.

• 1403 Printer:
  After a few mechanical tune-ups and availability of full 50-Hz power, the 1403 should print under control of the 1401.

• 729 Tape:
  Apply power, test motors, and install new belts. After full 50-Hz power is available, begin testing tape control electronics. An ex-IBM machinist in San Jose should be available to re-rubberize the capstans and the IBM Almaden machinist will continue making replacement items.

• Software:
  Organize and plan for a team "1401 architecture and intro to programming" class and the eventual, general "hands-on programming experience" class. Acquire and write demo and test programs. Decide on whether/how best to embark on writing/modifying a 1401 simulator and/or GUI. Read in the remainder of the 1401 punched cards and tag with associated metadata.

Issues:

• 50-Hz power:
  If there are problems with procuring/installing the larger power converter, restoration progress will slow.