TM 55-4920-412-13&P n. Shift Register Drive, ANA-DIG UPDATE, Internal Clock,    Reset    Pulse,    Clock    Inhibits,    Test    Freq,    PIS Control Auto Dim, DIG Display Update (Oscillator Board A6), Circuits. (1) Set ON-OFF-SIM ONLY to OFF. (2) Connect    test    equipment    as    shown    in Figure 4-1, unit tester connected. (3) Disconnect Oscillator Board (A6) from unit Test and reconnect extender board to oscillator board. (4) Connect   OSCILLOSCOPE   between   test loops  30  (HI)  and  44  (LO)  (Shift  Register  Drive).    Set Power to ON. (5) Set INTER CAL SELECT to position 21. (6) Set ANALOG SET switch STOP/SLOW/FAST to STOP and THEN SLOW. Oscilloscope   will   display   positive-going   square   wave pulses 4.5 to 5.5, Volts peak to peak (Vp-p).  If not, see Troubleshooting Table 4-32. (7) Set ANALOG SET switch to FAST. (8) Oscilloscope    will    display    positive-going square   wave   pulses   4.5   to   5.5   Vp-p.      If   not,   see Troubleshooting Table 4-32. (9) Place   ANALOG   SET   to   STOP   position. Oscilloscope will indicate ground. (10) Place  ANALOG  SET  to  FAST.    Interface Monitor   will   reset   after   counting   1827.      If   not,   see Troubleshooting Table 4-32. (11) Disconnect  from  Test  loop  30  after  setting power to OFF. (12) Connect  oscilloscope  counter  to  test  loop 38 (Digital display Update and clock inhibits).  Set Power to ON. (13) Oscilloscope    will    display    negative-going digital   update   pulses,   4.5   to   5.5   Vp-p.      If   not,   see Troubleshooting Table 4-32.  Repeat technique (11) and (12)  above  for  test  loop  28  for  negative-going  update pulses. (14) Set  Power  to  OFF  and  repeat  technique (11)  and  (12)  above.    Disconnect  oscilloscope  from  test loop  28  and  reconnect  to  each  test  loops  31,33,35,29, one  at  a  time.    Oscilloscope  will  display  positive-going clock  inhibit  pulses  4.5  to  5.5  Vp-p  for  each  connection. If not, see Troubleshooting Table 4-32. (15) Set power to OFF and disconnect oscilloscope from test loop 29. (16) Connect     oscilloscope     to     test     loop     4 (Analog-Digital Update Pulses). (17) Set Power Switch to ON and place Analog Set switch to SLOW. (18) Oscilloscope   will   display   negative   going update  pulses  between  4.5  and  5.5  Vp-p.    If  not,  see Troubleshooting   Table   4-32.      Repeat   technique   (15) through (18) above for test loop 9. (19) Set  Power  Switch  to  OFF  and  disconnect from test loop 9 and connect oscilloscope and frequency counter to test loop 26 (Internal clock). Table 4-31.  Signal Data Converter Section Unit Tester Digital Voltmeter Indications (vdc) Switch Settings Pin Connections Min Max CLOCK INHIBIT to ANA J8 Pin 24 45 5.5 CLOCK INHIBIT to DIG J8 Pin 25 4.5 5.5 CLOCK INHIBIT to DIG J9 Pin 36 4.5 5.5 CLOCK INHIBIT to ANA J9 Pin 37 4.5 55 P/S CONTROL fully CW and P/S CONT to REMOTE ILS test point 4.5 5.5 (connect jumper between J3-26 and J3-27) 4-58  Change 2