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IBM 727 Manual Of Instruction

Magnetic tape unit and tester, electronic data-processing machines
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IBM
T R A D E
M A R K
727
magnetic tape unit
and tester
e l e c t r o n i c d a t a - p r o c e s s i n g m a c h i n e s
customer engineering
manual of instruction
Form 22-6681-0

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Summary of Contents for IBM 727

  • Page 1 > ' T R A D E M A R K magnetic tape unit and tester e l e c t r o n i c d a t a - p r o c e s s i n g m a c h i n e s customer engineering manual of instruction Form 22-6681-0...
  • Page 2 Copyright 1956 by International Business Machines Corporation 590 Madison Avenue, New York 22, N. Y. Printed in U. S. A. Form 22-6681-0...

  • Page 3: Table Of Contents

    C O N T E N T S 727 MAGNETIC TAPE UNIT AND TESTER, MODELS I AND II Page Page 1.0 INTRODUCTION 11.0 MISCELLANEOUS 11.1 Charts 2.0 MACHINE SPECIFICATIONS 11.2 Select and Ready 75. 01 Tape Drive 11.3 Read-Write Status 75.02 11.4...
  • Page 4 Page 15.2 Adjustment of Head 17.0 PREVENTIVE MAINTENANCE Assembly (Figure 18) 15.3 HeadWear 18. 0 TYPE 727 RELAY WIRING 15.4 Removal and Adjustment DIAGRAM of Tape Cleaner 15. 5 Drive Clutch Assembly 19.0 727 TAPE DRIVE TESTER 15.6 Vacuum Unit 19.1...
  • Page 5 NOTICE THE text and illustrations in this manual have been prepared for teaching purposes and as an aid for learning the 727 Tape Drive and the Tape Drive Tester. All material was prepared from information relative to production at a given level.

  • Page 7: Introduction

    MODELS I AND II INTRODUCTION The Type 727 magnetic tape unit is designed to provide storage and reading of large amounts of sequential information on a magnetic tape. It is controlled largely from an external source with certain automatic functions contained within the unit.

  • Page 8: Machine Specifications

    This change in lateral dimension pre­ sents a problem of storing and using the tape on the 727 when the relative humidity varies over a wide range. The accurate guiding of the tape to the sensing heads de­...

  • Page 9: Capacity And Speed

    Temperature variations are secondary in comparison to humidity. If the tape is stored at about 70°F, no departure from the specified width should be observed. 6.0 "Tape Handling.” 2 .4 CAPACITY AND SPEED It is possible to write information in any of seven tracks across the face of the tape.

  • Page 10: Principles Of Storing Information

    3. 0 PRINCIPLES OF STORING INFORMATION MAGNETIC THEORY A magnetic material is one that can be polarized or partially polarized when placed under the influence of a magnetic field. For every magnetic material, a B-H curve can be plotted showing the resultant flux densities in the material when placed in the influence of a varying magnetizing force.
  • Page 11 When switch 1 is closed at time T^, current generator E-^ (Figures 3 a and 3b) cause the current 1^ to flow through the coil as indicated and a flux path is set up as shown, using the right hand rule. Because this flux path extends into the magnetic material on the tape, the domains in the material line up in the direction of the flux path.

  • Page 12: Physical Description

    4. 0 PHYSICAL DESCRIPTION The 727 magnetic tape unit is built on a frame about 2f x 2T 2" x 5f3 -3 /4 M . Mounted on the front of the frame are the reels, vacuum columns, read-write and erase heads and the tape driving pulleys and capstans.

  • Page 13: Split Idlers- Tape Alignment

    the coil is caused to move downward, called the "stop" position, both moving pulley forks pivot away from their respective drive capstans. 4 .2 .1 Forward-Reverse Magnet Assembly For only one moving pulley to cause driving at a time, it is necessary to bias the linkage to the right or left.
  • Page 14 To allow installation of tape by the operator and also to provide freedom of move­ ment during high-speed rewind, the upper plate is moved upward leaving a gap of about 27/32 inch between the erase head and the read-write head assembly. During the time when tape is being transported through the machine for reading or writing, the upper plate is down causing the assemblies to be in close contact with each other.

  • Page 15: Reel Drive Clutches

    source and the cell. However, if the tape breaks, the light source strikes the cell and stops the machine. 4. 5 REEL DRIVE CLUTCHES Each tape reel is mounted on a hub protruding from the upper front plate of the machine.

  • Page 16: 4. 6 Vacuum Columns And Vacuum-Operated Switches

    4. 6 VACUUM COLUMNS AND VACUUM-OPERATED SWITCHES The vacuum columns are vertical columns of rectangular cross section. The in­ side dimensions are 2 -1 /2 " x .510 (+ .002", - .000"). The front face of the vacuum column is transparent so that tape can be observed at all times. The top of the vacuum column is open and the lower end is connected to a manifold leading to a vacuum pump that maintains a vacuum of about eight inches of water.

  • Page 17: Motor Drive

    At the bottom of each vacuum column, separating the column from the manifold, is a flapper valve. This valve is similar to a door, held open under spring tension. A rush of air down the column strikes the flapper valve and closes it. Thus, the flapper valve and its associated m icroswitch, give an indication as to whether tape is in the vacuum column.

  • Page 18: Head-Raising Mechanism

    When this solenoid is energized, the horizontal shaft is rotated counterclockwise (as viewed from the left side) causing the arm and fork at (4) to push the capstan mechanism to the rear. Also attached to the solenoid armature is a dash-pot arm to pull the plunger in a dash pot, cushioning the action of the capstans.

  • Page 19: File Protection

    4.12 FILE PROTECTION A device is provided to prevent writing on a reel of tape if so desired. This device consists of a groove cut in the rear side of the file reel and an associated ring which fits into the groove. If the ring is not placed in the groove, writing is suppressed but reading is allowed.

  • Page 20: Panel Buttons And Lights

    5. O PANEL BUTTONS AND LIGHTS (FIGURE 5) Located on the reel door of the tape unit are the operating buttons and lights. These may be operated if the door interlock switch is transferred. Select Switch. This switch is rotary type, located in the center of the group. It is used to set the tape unit to any one of the ten addresses.

  • Page 21: Tape Handling

    TAPE HANDLING Because foreign particles can reduce the intensity of reading and recording pulses by increasing the gap between the tape and the head, take the utmost care to protect the magnetic tape from dust and dirt. 1. Keep the tape in a dust-proof container whenever it is not in use on a tape unit.
  • Page 22 The procedures outlined above apply to handling tape in a 701 installation as well as 702 and 705 installations. Customer engineers and other IBM personnel should take special precautions to follow the tape handling recommendations to show, by example, the care required to insure good tape performance.

  • Page 23: Load-Rewind Operation

    7. 0 LOAD-REWIND OPERATION Initiate a load-rewind operation by pressing the load-rewind button. Doing this always has the same end result; the tape is moved until the load point stops beneath the load-point photo cell. In this discussion of a load-rewind operation, assume the following initial conditions: The power cable is connected to a control unit as a source of power.
  • Page 24 The following relays can pick with the 48v DC supply, because the tape unit is assumed to be unloaded. Remarks Systems Sequence of Conditions Operation R21, R26, unload, These relays were latched are latched. the last time the machine was unloaded. Pick R i l , R22, R21-4n/o unload.
  • Page 25 • • Conditions Remarks Systems Sequence of Operation • so tape can be threaded on the machine easily. • • Thread tape on machine. • Push load-rewind button. • Pick R40, rewind R 42-3n /c, relay driver R40 has no hold circuit. (75.08), manual load- •...
  • Page 26 Systems Sequence of Conditions Remarks Operation 75.10.02 Time delay mtr. HD7 pt. starts. Pick DPI, take R6BLn/o Prepare to run take-up up mtr. reverse. mtr. in reverse. Pick HD8, retract R6AUn/o capstans. Energize capstan HD8 pt. Prepart to extend cap­ retracting solenoid.
  • Page 27 • • Systems Sequence of Conditions Remarks Operation • Manual start line R9BL, R10BL, R31-6 Start to the moving coil goes up. is incidental at this time. • The tim e-delay point closes. • Pick HD6, take- Time delay point up mtr.
  • Page 28 Systems Sequence of Conditions Remarks Operation 75.10. Q1 Full power to both R4 pts. stop clutches. Drop R2, rewind. "Caps out" microswitches Both capstans are fully extended. Drop R3, R31, r e ­ R2BL wind. Drop R5, R6, R2AU start slow rewind, and HD 7, time delay.
  • Page 29 output of the SS,p goes up, allowing the relay driver at 5F (75.04) to conduct, latch picking R42, load point (75. 09.03L). Systems Sequence of Conditions Remarks Operation Drop R35, R36, R42-1 rewind status. Drop R33, r e ­ R35-2 verse.

  • Page 30: Motion Control

    8. 0 MOTION CONTROL The mechanical linkage used to provide motion of the tape is described under "Physical D escription." The operation of this linkage is dependent on energizing the moving coil in either direction. The control of this operation is covered in the following descriptions.

  • Page 31: Unload Operation

    • • • UNLOAD OPERATION • To remove a reel of tape and mount a new reel, the unit must be in an unload status. Unload status may be obtained by pressing the reset button and then the un­ load button on the front panel. (Pressing the reset button is only necessary if the •...
  • Page 32 Remarks Sequence of Conditions Systems Operation Caps in microswitch Pick R7, caps in. 1/2 pwr. to both stop Pick R4, clutch. R7AL, R21-2n/o clutches. Take-up mtr. starts in Pick HD6, take- R7AUn/o up mtr. start. forward direction. • • • •...

  • Page 33: High-Speed Rewind

    10. 0 HIGH-SPEED REWIND When a tape has been completely written or read, the bulk of the tape is on the machine reel. Because time is a prime factor in the operation of this unit, it is best to accomplish a rewind to the file reel as fast as possible. A high-speed rewind may be initiated when at least one-half inch of tape is on the machine reel.
  • Page 34 Systems Sequence of Conditions Remarks Operation Pick R4, clutch. R7AL, R2 hold circuit 1/2 power to stop clutches Pick HD6, take- R5AU, R6BL, R7AUn/o Start the take-up motor. up motor start. Start raising the head cover, and turning the reels to pull tape from the columns.
  • Page 35 Systems Sequence of Condition Remarks Operation Pick R5, R6, start Arm switch Start time delay motor. slow rewind, and HD7, time delay. Drop R12, high R5BL Turn power off rewind speed, and DP3, mtr. rewind mtr. 10.01 1/2 power to right R12BL Start slowing down.

  • Page 36: Miscellaneous

    11.0 MISCELLANEOUS 11.1 CHARTS Systems pages 7X. 01.02 through 7X. 06.02 contain charts showing pluggable unit locations, cable connectors, fuses, and relays. 11. 2 SELECT AND READY 75. 01 A tape unit is ready for selection when the tape has been loaded into the columns, the reel-d oor interlock is closed, the unit is not rewinding, and the start key has been pressed.

  • Page 37: Tape Indicator

    11.4 TAPE INDICATOR 75. 03 The tape indicator is a trigger that may be used to indicate certain conditions sensed within the tape unit. It may be controlled externally or internally. The trig­ ger is turned on internally by sensing the reflective spot at the end of a reel of tape, when writing.

  • Page 38: Read Pre-Amplifier

    Raising the manual reverse line raises the reverse line. This is the method used while rewinding. 11. 8 READ PRE-AMPLIFIER 75. 06 To read from tape, a tap is taken off the read-write head in 75. 07 and tied to an amplifier circuit 75.06.

  • Page 39: Write Echo

    11.10 WRITE ECHO For checking purposes, a write echo pulse is developed and sent back to the external circuitry. This pulse is taken at the cathode of the 1 ^ ^ . It is AC coupled to an Ig to feed a K p which in turn brings up the w rite-echo bus.

  • Page 40: File Protection

    The other way to initiate a rewind operation is from the load-rewind button on the front panel. This button in 75.09. 02 brings up "manual load rewind" which com ­ bines in 75.08 with "read status" to bring up "rewind PU re la y ." "Read status" is used because, if the unit were in write status, the read-write and erase heads would conduct and information would be destroyed as the tape was passed by these heads.

  • Page 41: Resume Of Lines Entering And Leaving Tape Units

    12.0 RESUME OF LINES ENTERING AND LEAVING TAPE UNITS The control lines entering and leaving the tape unit are pictured in Figure 15. A brief functional description of each, line is given below. Select Lines (75.01) (10 lines). The select lines are routed from external con­ trol;...
  • Page 42 Turn on TI (75. 03). This line originating in the control system turns on the tape indicator in the selected tape unit. Turn off TI (75. 03). This line originating in the control system turns off the tape indicator in the selected tape unit. Write Pulse (75.02).

  • Page 43: Sources Of Trouble

    13.0 SOURCES OF TROUBLE 13.1 SIGNAL DROP OUT The nomenclature of this term indicates that the voltage amplitude of the signal was decreased to such a value that it could not be correctly interpreted by the detect­ ing equipment as a one. In general, there are two main causes for this phenomenon. 1.
  • Page 44 Specifically, it is necessary to minimize skew so that the closely spaced characters on tape can be correctly interpreted and distinguished from each other. Figure 16 illustrates three of the causes of skew in an exaggérated manner. The effects of skew are magnified when the skew written into a tape by one tape drive is opposite to the skew associated with reading on another tape drive.
  • Page 45 location of the left-hand pole tip (effective). Therefore, if the effective air-gap widths of two tracks are different, they will exhibit skew on their own tape. Air gap width differences are caused by difference in skim material thickness and fit of the pole pieces against the skim material.

  • Page 46: Service Aids

    14.0 SERVICE AIDS 14.1 FUSE REPLACEMENT The fuses for the tape drive are located on the lower left, facing the rear of the machine. The left row of fuses are for the AC lines; the right row are for DC lines. Because a blown fuse leaves the tape drive in an unknown status, the tape drive door should be opened before a blown fuse is replaced.

  • Page 47: Moving Coil Circuitry

    14,3 MOVING COIL CIRCUITRY For satisfactory operation, the moving coil must be excited by 50ma. Refer to section 1 5.8 .8 . Marginal conditions in the moving coil circuitry can be determined by bias check­ ing the 140v supply to its lower limit. These conditions show up as increase in start- stop time, i .

  • Page 48: Removal, Assembly And Adjustment Procedures

    Adjust the position of the erase head to provide . 008" to . 010" clearance be­ tween it and the read-write head, when the read-write head cover is fully down. Use a piece of IBM card stock as a gage, and adjust to the point where there is just no drag when moving the card.
  • Page 49 1 5 ,2 .4 Microswitch Adjustment The head up switch is wired n /o and should be adjusted to transfer within 1/4 revolution of the upper limit stop when head is going up. The head down switch is wired n /c and should be adjusted to transfer within 1 /4 revolution of the lower limit stop when the head is going down.

  • Page 50: Headwear

    then be zero. (Turning screw clockwise causes track C to lead track 1 with tape moving forw ard .) The fluctuations in skew (flutter) may not exceed 6 usee, otherwise tape guid­ ing must be improved. (See sections 13. 3 .3 , 13.3. 5 and 15.2. 5.) 7.

  • Page 51: Drive Clutch Assembly

    bulb and photo cell to no tape existing). This peak voltage swing is not to be less than ten volts using a 2 0 ,000-ohm /volt voltmeter. Physically adjust the reflector plate by using the adjusting screw. This screw can be secured by the setscrew to lock it into position.

  • Page 52: Vacuum Unit

    5. Remove these collars. 6. Remove the screws entering the rear of the shafts. 70 Remove the rear plate, which is held by six screws and four dowels. The clutch and shaft assemblies may now be removed from the fram e. Note carefully the position of any shims;...
  • Page 53 screws for the angle clamps too tightly, as they can distort the shape of the clamps and lucite. The columns are adjustéd to be parallel to the lower main plate. On earlier ma­ chines (two holding screws to the lower main plate), adjust as follows: remove the lucite cover angle clamps and loosen the two manifold mounting screws at the base;...

  • Page 54: Drive Capstan Mechanism

    Unscrew the four bolts that mount the pump. Lower the pump out to the right of the machine. Be careful that the pump inlet pipe does not strike the floor of the machine, possibly jamming the impeller blades. 1 5.6 .6 Vacuum Column Tape Guide The guide fits in each vacuum column and bears on the tape just before the tape reaches the moving pulley.

  • Page 55: Moving Coil Unit

    15. 7.4 Capstan Retracting Mechanism Adjustments (Figure 13) The horizontal operating shaft should be free of binds. Accomplish this by shift­ ing the position of housings. The solenoid plunger and linkage should be free of binds. Shift components under the mounting screw s. The pin of the solenoid latch assembly should be as close as possible to the top of the solenoid without restricting the sliding freedom of the latch pin.
  • Page 56 This cleaning may be done with a piece of IBM card covered with Scotch Electrical tape, adhesive-side out. The complete magnet assembly may be positioned on the lower front plate so that the moving coil does not bind in the cavity.
  • Page 57 Check for binds or rust at armature pivot. Loosen the yoke holding screws (7) and squeeze forward and reverse magnet yokes together, until the armature is held firm ly between them. This positions the magnet yokes and armature for proper sealing of the armature when final adjust­ ments are made.
  • Page 58 At this time, with the forw ard-reverse magnet de-energized, the forw ard- reverse armature should be centered, whether the moving coil is in a start or a stop status. The final start-stop adjustment is checked by the use of the scope and should be set at 4.

  • Page 59: Miscellaneous Adjustments

    The " start envelope" should be sim ilar to Figure 24. After calibrating the scope sweep circuit, use a positive external trigger input from 03J-P2. Obtain an input signal of 20 volts (peak to peak) from Fn. See section 1 9 .4 .2 . Variations from this envelope can be caused by gap adjustments, the m oving-coil wave form , or mov­...
  • Page 60 15.9. 2 Machine Reel Brake Adjust the machine reel brake with the potentiometer so that the reel is stopped when about 1/16" of tape is on the reel after rewinding from a full reel of tape with the machine-reel sensing-arm switch adjusted as indicated above. 15.9 .3 Time Delay Adjust time delay so that it runs for about 1 -1 /2 seconds after the machine reel...
  • Page 61 NOTE: When removing the tape break light bulb, care must be taken to return the special washer which is located between the bulb and its socket. The bulb will not remain in place within the assembly without the washer. 1 5.9 .8 Write Current Measurement The write current should be indicated by a reading of 56v ±...

  • Page 62: Lubrication Specifications

    Inspect oilite bearings in capstans housings and moving pulley periodically for wear or gum accumulation. Replace or clean as necessary. Split idlers and rewind idlers, moving pulleys and bushings. (Lubricate sparingly.) Dashpot cylinder. (Use light film s of IBM 6.) Capstan belt idler pulley. (Lubricate as required.) File protection plunger.

  • Page 63: Unit

    The pressure pad can be cleaned best with an IBM typewriter brush (P/N 1018992). The other surface may be cleaned with a lint- free cloth or cotton tipped stick dampened with a suitable solvent.
  • Page 64 Lamps (monthly). Check functional operation of lamps. Refer to EDPM CEM 86 for proper resistance values. Tape drive maintenance with tape tester (one unit per shift). Follow this check list as closely as possible when removing a tape unit from the system. additional information, see CEM 180.

  • Page 65: Type 727 Relay Wiring Diagram

    18. 0 TYPE 727 RELAY WIRING DIAGRAM The following diagram is a partial duplication of the tape drive unit systems dia­ gram. It should be used as an aid in learning, not in servicing, the machine. For simplicity, the wiring is not shown point to point.
  • Page 66 WIRE CONTACT RELAYS DUO RELAYS POINTS POINTS N O . COIL N O . COIL BU BL ApCt FpCt LpKt LpKt MISCELLANEOUS AC-DC Fuse Micro-switch Relay PICK POINTS Capstans in micro-switch HD 1 Capstans out micro-switch HD 2 Door interlock HD 3 F .
  • Page 67 • • • • • • • • • • • • • • •...
  • Page 69 To Fuse 13...
  • Page 73 To Fuse 13...
  • Page 77 Rew. Intik 75.08 Rev. Sol Reverse —>*------ — Tl 75.05.02 o £ n > # ro Fwd. Sol . Rewind 75.08 Rewind P.U R40 I Tape Break L P £ 75.03 Tape Break L.P.Pic k — «p LP 75.04 Load Point | R42 Drop L .

  • Page 79: Tape Drive Tester

    19.1 GENERAL 19.1 .1 Purpose The tape drive (727) tester (TDT) is designed to test mechanical and electrical functions of the Type 727 tape drive. The TDT tests all of the signals coming from and going to the drive. It supplies power to the drive through the normal power connector.
  • Page 80 Bit Switches. These seven switches determine whether ones or zeros are written in the corresponding tracks when the tape is moving in write status. Go-Fb. This switch directs the output of the go-backward trigger (T^) in the TDT either to the go line or the backward line in the tape drive unit. Manual Forward-Manual Reverse.

  • Page 81: Oper At Ions

    1 9.2 .2 Hubs Echo Bus, The write echo of the track selected by the response select switch can be observed at this hub. Read Bus. The output of the pre-am p selected by the response select switch can be observed at this hub. Go-Fb.
  • Page 82 "reset write triggers" pulse could coincide with the fall of a write pulse. In this case (Case B, Figure 30) assuming all ones were being written, at time T^ some of the write triggers might be turned on and some might be turned off. Then these triggers would be flipping out of step with each other for the rest of that writing period.

  • Page 83: Test Procedures

    The TDT and tape drive can be left to write and rewind for a period of* time to check the reliability of high-speed rewind. 19.4 TEST PROCEDURES 1 9.4 .1 Mechanical Adjustments of Tape Drive The following chart lists the conditions necessary to adjust the forw ard-reverse magnet and the stop capstans in the drive unit, referred to in section 1 5 .8 .4 of this manual.
  • Page 84 switch while the tape is in motion. (Damaged tape may result when tape motion is changed in a go status.) 19.4. 3 Measurement of Skew A master tape (P/N 503928) for checking skew of the read-write head is provided for every installation,, This test can be made using the tape drive tester.

  • Page 85: Purpose Of Relays

    20. 0 PURPOSE OF RELAYS R l, 18, Run (09.04) They are always picked except when unloaded. When dropped, they indicate a failure in one of the machine interlocks, such as a blown fuse, tape breakage, or DC power failure. 1AU, 1BU (10.01) When down, they allow full brake to both stop clutches.
  • Page 86 This is for added protection to insure that the tape is file 31-3 protected when rewind is initiated, before R35 is picked. 31-4 (09.01) Pick the rewind status relays. 31-6 (09.02) During load rewind, until the capstans are extended, the R6, 8, 9 and 10 pts.
  • Page 87 R8, Head cover not Pick R8 when the head cover is not all the way down. Hold it until the head cover is all the way down and tape is in both down (09. 05) columns. This runs the capstan motor only when using the capstans 8AU (09.06) N/C or when moving the capstans in or out.
  • Page 88 Latch trip the tape break relay when unloading after a tape 22-6 (09.03) break. Drop R2 if the unload button is pressed during load rewind. 22-7 (09.04) 22-8 (09.06) If a condition existed where the capstans were extended while in unload status, the capstans would automatically be r e ­ tracted.
  • Page 89 20-1 (09.04) N/C It prevents unloading or load rewinding a tape unit that is ready, without first pressing the reset button. Hold for R20, 20-2 (09.03) The conditions as stated for R20 are a partial requirement for bringing up the machine ready line. 20-3 (09.02) When closed, it provides a constant reset to the read-w rite status trigger.
  • Page 90 tester can also be used to pick R34 when the tape unit is not in rewind status. 34-1 (09.02) Bring up the manual start line in order to energize the mov­ ing coil and move tape. They pick when the load rewind button is pressed (31-4) if R35, 36, Rewind status the tape is not already at load point.

  • Page 91: Tape Drive Cem Listing

    Ground connection - SP receptacle Logic changes RC networks across relays New EDPM part numbers -12 clamp reset diodes ™ Test tape storage Moving coil circuits Dummy fuses “ Tape interlock change Air filters 727 check-out procedure using tape drive tester...
  • Page 93 " 0 3 9 0 0 35 FIG U RE 1. BIT P O S ITIO N S O N TAPE CURRENT GENERATOR FIG U RE 3c.
  • Page 94 M A C HIN E REEL S E N S IN G ARM M A C HIN E REEL UPPER M A IN PLATE TAPE VA C UUM SW ITC HES FIG U RE 4 . F R O N T V IEW FILE TAPE SELECT...
  • Page 95 PATH OF TAPE THROUGH MACHINE FIGURE 6...
  • Page 96 L E F T STO P R IG H T STO P CAPSTAN CAPSTAN M O V IN G P U LLEY M O V IN G PU LLEY M EC HA N ISM SHO W N IN A FORWARD - STO P S TA TU S FIG U RE 7.
  • Page 97 SPLIT IDLER ASSEM BLY FIGURE 8...
  • Page 99 CLUTCH HOUSING POWDERED IRON AND GRAPHITE MIXTURE FIGURE 10 MAGNETIC CLUTCH...
  • Page 100 PUSH ROD DIAPHRAGM VACUUM COLUMN SWITCHES FIGURE II...
  • Page 101 CAPSTAN MOTOR FORWARD MOTOR BACKWARD MOTOR...
  • Page 102 LATCH FIGURE f3...
  • Page 103 + 140 + 140...
  • Page 104 SELECT LINES (10) SELECT 8 AT LOAD POINT TYPE 727 SELECT a REWIND STATUS TAPE DRIVE UNIT START REWIND SEL. a TAPE IND. OFF TURN OFF TAPE IND. SEL. a TAPE IND. ON > "" TURN ON TAPE IND. S E T...
  • Page 105 Back Plate • Heads i«r FIG U RE 16a. TO P V IEW O F REA D IN G HEAD SH O W IN G HEAD SKEW (M ECHANICAL) FIG U RE 16b. TO P V IEW O F REA D IN G HEAD SH O W IN G POOR HEAD A LIG N M E N T Back Plate Tape...
  • Page 106 Turn O ff Erase Head Reset R/W Status T g r ., Turning O ff W rite Heads -Stopping Distance Information - Record W ritten; A ll Bits Already on Tape Tape Motion Correct Polari+y FIG U RE 17a Tape Motion Incorrect Polarity FIG U RE 17b FIG U RE 17.
  • Page 107 FIG U RE 18. HEAD A SSEM BLY A D JU S TM E N TS...
  • Page 108 TA P E C L E A N E R FIG U R E: 19...
  • Page 109 VACUUM COLUMN A D J U S T M E N T F IG U R E...
  • Page 110 DRIVE MOTOR PULLEY CAPSTAN DRIVE BELT TENSION FIGURE 23 (R E A R V IE W S)
  • Page 111 V ert. Cal. 10 Volts/Major D iv . Hor. Cal. 2 Msec/Major Div . Signal Reduction due to A small non-drive gap; having a tendency to drive tape at both capstans. Worn pin in capstan drive pulley. Pressure pad adjustment. Keep this reduction at a minimum The signal level should be stable by 7-1/2 msec.
  • Page 112 V e r t . Cal . 20 V o lts/M a jo r Div . H o r . C a l. 4 M sec/M ajor Div . FIG URE 26. REVERSE M A G N ET TRA N SFER VER.
  • Page 113 CONTROL UNIT TAPE DRIVE TESTER FIG URE 28. TAPE DRIVE TESTER C O N N E C TIO N S...
  • Page 114 ° c j) © c j) © FIG URE 29. 727 TAPE DRIVE TESTER T 100 100 usee Reset W rite Tg rs . W rite Pulses FIG U RE 30. TAPE TESTER - RESET W RITE TRIG G ERS...
  • Page 115 (05C) , R 2I,26 (04A ,05F) UNLO/i D iR2BL R7 (05G) CAPSTANS IN CAPS IN M.SW. RI4(0IH) P^OTO LIGHT R81Q5F) HEAD COVER NOT DOWN H.C. ^ DOWN RII,22(Q5D) UNLOAD M.SW. H R 2 I-4 RI3(Q6H) CLUTCH TRANSFER RlIBU HR3BU RI7 (QIC) POWER ON EXTER N AL HD3(06H)
  • Page 116 FIGURE 32 HIGH SPEED REWIND...

  • Page 117: Introduction

    INTRODUCTION 22.1 MECHANICAL PRINCIPLES The differences between the Model I 727 and the Model II 727 are minor, consist­ ing only of cover changes. The Model III changes are described in this appendix; the mechanical changes are described in this section.

  • Page 118: Electronic Circuits

    II. Some circuits have been omitted. They were directly concerned with relays that have been omitted. The changes are as follows: 727 Models I and II Model HI Change (Omissions on the Model IH Systems) 75.03 76.03 AND circuit E32F, which AND'ed T trewind inter­...

  • Page 119: Relay Circuits

    23.0 RELAY CIRCUITS 23.1 LOAD, IN LOW-SPEED REWIND AREA This is the relay operation sequence for a load operation when less than one-half inch of tape is wound on the right-hand reel. The machine is in the following condition before the load-rewind button is depressed, Both reels are on machine with enough tape threaded across to the right reel to have the load point reflective spot on that reel.

  • Page 120: Tape Motion Under Calculator Control

    The load-point reflective spot is sensed and R25 picks. Relay 25-3n /c points open, dropping R12. Relay 1 2 -ln /o points open, dropping +48 volts to manual r e ­ verse and manual start. This causes the tape drive to stop setting in a loaded con­ dition.

  • Page 121: High-Speed Rewind

    leg of AND circuit T03JC3F (76.08). Select and ready conditions the lower leg. The resulting up level conditions the relay driver T03J4B; R21 is picked. If R21 is picked when less than one-half inch of tape is on the right reel, a slow-speed rewind operation results (Figure 36).

  • Page 122: Purpose Of Relay Points

    24. 0 PURPOSE OF RELAY POINTS Picked when the bellows switch closes. Senses failures such R l, Run Relay (76.09.01) as fuse bail operation, loss of vacuum in either column, photo­ cell bulb failure, or bellows switch operation during a normal operation.
  • Page 123 5AU (76.09.01) Drops relay 1 (run) if tape is not in the left column during normal operation. 5AL (76.09.02) Drops R27 (GO status) if tape is not in left column during normal operation. 5BU (76.09.09) Interlock on pick of R23 (high-speed rewind status). Tape must be out of left column before entering high-speed rewind.
  • Page 124 Drops "not file protect" to 76.02. Keeps write status down 10-6 (76.09.07) when drive is in unload status. Picks when the load-rewind button is depressed. R12, Rewind status (76.09.08) 12-1 (76.09.02) Supplies a circuit for +48 volts to the 9-3 points so R27 can pick and the manual-reverse line can be powered.
  • Page 125 16-3 (76.09.09) Opens the circuit around the load-point and tape-indicator photo-cell lamps when drive is unloaded. 16-4 ( 76.09.06) Drops the circuit to the head lock solenoid when the drive is unloaded. R17, Power on reset Picks when +48 volts is up and holds until 48 volts drops. 17-1 (76.09.01) Drops R l, HD1, HD2, and HD3 if +48 volts drops.
  • Page 126 Picks at any time tape is to be fed by the drive capstans. R27, GO status (76.09.02) 27-1 (76.09.03) Brings up "manual sta rt." DPI, Take-up motor Picks during load-rewind and high-speed rewind operations. reverse (76. 09. 08) Switches two phases to the take-up motor allowing it to run DPI A &...
  • Page 127 Start push button Picks R13 when depressed. (76.09.08) Head-up switch The points shown are the normally open points of a m icro­ (76.09.09) switch. They are closed when the head is up.

  • Page 128: Adjustments

    25.0 ADJUSTMENTS 25.1 CAPSTAN-IN AND CAPSTAN-OUT SENSING SWITCHES Adjust the sensing switches with adjusting fork C (Figure 34) so that the differ­ ential of the switch (the point where switch points transfer) is centered in the fork gap. Position the sensing switches on the outboard sides to sense capstan out. this by pushing the capstan forward to drive position and aligning the permanent mag­...
  • Page 129 " iS ' i ^ A ft r \ _ ----------------------- 1 “ — ■ —-..WÊF ■ (B) Capstan Retracted FIG U RE 33. C APSTAN DRIVE M O TO R , 727 M O D EL III...
  • Page 130 Right Capstan Motor (Bottom View) Sensing Switch Assy. (Capstan Out) FIG U RE 34. CAPSTAN S E N S IN G SW ITC H ES, 727 M O D EL III...
  • Page 131 Tape Drive In Loaded Cond.J F IG U R E 3 5 . LO A D R E W IN D IN LO W - S P E E D A R E A , 727 M O D E L III...
  • Page 132 At Load Point- Stops F IG U R E 3 6 . M A N U A L C O N T R O L O F TA PE M O T IO N , 727 M O D E L III...
  • Page 133 A t Load Po int---- sequence. Stops- F IG U R E 3 7 . H IG H - S P E E D R E W IN D , 727 M O D E L III...
  • Page 134 Relay 17 and 7 Up and Bellows Sw. Operates-J Door Interlock Switch Drive In Unloaded Condition-1 closed throughout this Sequence. F IG U R E 3 8 . U N L O A D , 727 M O D E L III...
  • Page 136 ■ v...

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