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Librascope/General Precision LGP-21 Hardware Maintenance Manual

This is the LGP-21 Hardware Maintenance and Training Manual supplied with the machine, page-scanned at 150 dpi, 11.5" x 8.5" (U.S. A size). It contains operation, theory of operation (including a complete algebraic definition of all the machine logic), memory alignment procedures and a complete set of logic diagrams, photographs and schematics.

  • Page cover, Front cover
  • Page i, Table of Contents
  • Page 1-1, Section I - Introduction
  • Page 2-1, Section II - Operation
  • Page 3-1, Section III - Theory of Operation
  • Page k-1, FLEXOWRITER FLOW CHART, Figure 4-7, part 1
  • Page 4-1, Section IV, Maintenance
  • Page 4-5A, 4.2.2 Program-controlled Carriage Return Operation
  • Page 4-8, 4.3 Flexowriter Relay Contact Information
  • Page 4-14, 4.4 Flexowriter Electrical Maintenance Specifications
  • Page 4-15, FLEXOWRITER FLOW CHART, Figure 4-7, part 2, AFU (rebuild)
  • Page 4-16, FIGURE 4-8, FLEXOWRITER TIMING CHART
  • Page 4-19, 4.6 Disc and Memory Head Maintenance Procedures
  • Page 4-20, 4.6.1 Main Memory Head Specifications
  • Page 4-21, 4.6.2 Main Memory Head Replacement and Adjustment Procedure
  • Page 4-23, 4.6.4 Recirculating Register Head Adjustment Procedure
  • Page 4-24, 4.7 Conversion of Deciman Track-and-Sector Addresses to Hexadecimal
  • Page 4-25, (Figure 4-16, Main Memory Head Locations)
  • Page 4-26, (Figure 4-17, Typical Signals)
  • Page 5-1, Section IV, Logic Diagrams
  • Page 5-2, Flexowriter Functions
  • Page 5-7, MEMORY CONTROL, L121 COMPUTER [typo] LOGIC DIAGRAM
  • Page 5-8, FIGURE 4-9, PHASE CONTROL LOGIC DIAGRAM
  • Page 5-9, FIGURE 5-7, LOGIC DIAGRAM, P & Q REGISTER
  • Page 5-9, FIGURE 5-8, LOGIC DIAGRAM, ARITHMETIC, LGP-21 COMPUTER
  • Page 5-11, FIGURE 5-9, FLEX-TALLY I/O LOGIC DIAGRAM
  • Page 5-12, FIGURE 5-10, TALLY P AND R LOGIC DIAGRAM [orig typo corrected]
  • Page 5-13, MEMORY CONTROL, 1 OF 3 SCHEMATIC
  • Page 6-1, Section VI, Schematics
  • Page 6-4, FIGURE 6-2, MEMORY CONTROL BOARD and SIGNAL REFERENCE LIST
  • Page 6-5, MEMORY CONTROL, 2 OF 3 SCHEMATIC
  • Page 6-6, FIGURE 6-3, MEMORY CONTROL BOARD and SIGNAL REFERENCE LIST
  • Page 6-7, MEMORY CONTROL, 3 OF 3 SCHEMATIC
  • Page 6-8, FIGURE 6-4 PHASE CONTROL BOARD and SIGNAL REFERENCE LIST
  • Page 6-9, PHASE CONTROL, 1 OF 2 SCHEMATIC
  • Page 6-10, FIGURE 6-5, PHASE CONTROL BOARD and SIGNAL REFERENCE LIST
  • Page 6-11, PHASE CONTROL, 2 OF 2 SCHEMATIC
  • Page 6-12, FIGURE 6-6, FLEX-TALLY I/O BOARD and SIGNAL REFERENCE LIST
  • Page 6-13, FLEX-TALLY I/O, 1 OF 2 SCHEMATIC
  • Page 6-14, FIGURE 6-7, FLEX-TALLY I/O BOARD and SIGNAL REFERENCE LIST
  • Page 6-15, FLEX-TALLY I/O SCHEMATIC
  • Page 6-16, FIGURE 6-8, [TALLY] P AND R REGISTER BOARD and SIGNAL REFERENCE LIST
  • Page 6-17, TALLY P & R BOARD, 1 OF 2 SCHEMATIC
  • Page 6-18, FIGURE 6-9, [TALLY] P AND R REGISTER BOARD and SIGNAL REFERENCE LIST
  • Page 6-19, TALLY P & R BOARD, 2 OF 2 SCHEMATIC
  • Page 6-20, FIGURE 6-10, [TALLY] P AND R REGISTER BOARD and SIGNAL REFERENCE LIST
  • Page 6-21, P & R REGISTER, 1 OF 3 SCHEMATIC
  • Page 6-22, FIGURE 6-11, [TALLY] P AND R REGISTER BOARD and SIGNAL REFERENCE LIST
  • Page 6-23, P & Q REGISTER, 2 OF 3 SCHEMATIC
  • Page 6-24, FIGURE 6-12, P AND Q REGISTER BOARD and SIGNAL REFERENCE LIST
  • Page 6-25, P & Q REGISTER, 1 OF 3 SCHEMATIC
  • Page 6-26, FIGURE 6-13, ARITHMETIC BOARD and SIGNAL REFERENCE LIST
  • Page 6-27, ARITHEMETIC, 1 OF 4 SCHEMATIC
  • Page 6-28, FIGURE 6-14, ARITHMETIC BOARD and SIGNAL REFERENCE LIST
  • Page 6-29, ARITHMETIC BOARD, 2 OF 4 SCHEMATIC
  • Page 6-30, FIGURE 6-15, ARITHMETIC BOARD and SIGNAL REFERENCE LIST
  • Page 6-31, ARITHMETIC, 3 OF 4 SCHEMATIC
  • Page 6-32, FIGURE 6-16, ARITHMETIC BOARD and SIGNAL REFERENCE LIST
  • Page 6-33, ARITHMETIC, 4 OF 4 SCHEMATIC
  • Page 6-34, FIGURE 6-17, DISTRIBUTION BOARD (S/N 21-40) and SIGNAL REFERENCE LIST
  • Page 6-35, LOGIC DIAGRAM, DISTRIBUTION
  • Page 6-37, CONTROL PANEL
  • Page 6-38, REAR PANEL
  • Page 6-39, LGP-21 SYSTEM ASS'Y CABLING DIAGRAM
  • Page 6-40, INTERNAL TALLY P & R BOARD TO TALLY PUNCH (Cable)
  • Page 6-45, POWER SUPPLY, L121 COMPUTER [not typo], ELECTRICAL SCHEMATIC DIAGRAM
  • Page 6-46, SCHEMATIC POWER SUPPLY
  • Page 6-47, SCHEMATIC, FLEXOWRITER, LGP-21, MODEL FIO
  • Page 6-48, TAPE READER, LGP-21 COMPUTER, SCHEMATIC DIAGRAM
  • Page 6-49, SCHEMATIC DIAGRAM, TAPE PUNCH, LGP-21 COMPUTER
  • Page 6-50, SCHEMATIC DIAGRAMS, BASIC LOGIC FUNCTIONS, LGP-21 COMPUTER [poor original]
  • Page 8-1, Section VIII, Computer Parts List
  • Page tpcover, Tape Perforator, Tally model 420
  • Page tpp1, Addendum (sic)
  • Page tpp2, Parts price list
  • Page tpw, Warrenty
  • Page tpxw, Table of Contents
  • Page tpxx, List of Illustrations
  • Page tpxy, Identification of parts
  • Page tpxz, Photograph
  • Page tp1, 1.0 Introduction
  • Page tp3, Figure 2, partially exploded view
  • Page tp4, Figure 3, capstan drive
  • Page tp6, 2.2 Perforator mechanism
  • Page tp7, Figures 4 and 5, Perforator assembly
  • Page tp8, Figure 6, Punch drive, sheet 1
  • Page tp9, Figure 6, Punch drive, sheet 2
  • Page tp12, 2.4 Punch head assembly
  • Page tp13, 3.3 Cycle length limitations
  • Page tp14, Figure 7, Perforator timing diagram
  • Page tp15, Figure 9, Wiring diagram
  • Page tp16, 4.0 Instructions for use
  • Page tp17, Figure 11, Tape guide adjustment
  • Page tp18, Figure 13, Lubrication points
  • Page tp20, 5.2 Cleaning
  • Page tp22, Table 5-1, Capstan drive tolerances
  • Page tp23, Figure 14, Escapement adjustment
  • Page tp24, Figure 15, Switch accessories
  • Page tp25, 6.0 Optional accessories
  • Page tp26, 6.2 Capstan commutator
  • Page tp27, Figure 16, Capstan commutator
  • Page tp28, Figure 17, Reel drive mechanism
  • Page tp30, Supplemental parts list
  • Page trcover, Tape Reader Manual, Tally model 424
  • Page triii, List of illustrations
  • Page trvi, Figure 5, Model 424PR plan view
  • Page tr1, Table of Contents
  • Page tr2, 1.2 Description
  • Page tr5, 2.2 Tape read head
  • Page tr6, 3.2 Switching action
  • Page tr7, Figure 8, Timing diagram
  • Page tr8, Figure 9, Wiring diagram for 34-pin connector
  • Page tr9, 4.0 Instructions for use
  • Page tr10, 5.0 Maintenance
  • Page tr11, Figure 12, Lubrication chart
  • Page tr12, Figure 13, Tape read head
  • Page tr15, Table 5.3-1, Capstan drive tolerances
  • Page tr16, Figure 18, Bidirectional tape splice
  • Page tr17, 7.0 Special accessories
  • Page tr19, Figure 21, Capstan commutator
  • Page tr20, Figure 22, Commutator timing
  • Page tr21, 8.0 Parts ordering and parts list
  • Page tr23, Figure 23, Model 424a parts list
  • Page tr25, Figure 24, Model 424c parts list
  • Page tr34, Warranty
  • Page tr36, Addendum
    • All works here unless otherwise specified are copyright 2026 by Tom Jennings. Permission is granted for personal use with no remuneration. Corporations or any organization or their agents, employees, consultants or other relationships human or otherwise, expressly prohibited without written permission.