TM5-6115-593-34 NAVFAC P-8-631-34 TO-35C2-3-463-2 5-8.  SYNCHROSCOPE. a.  Inspection.  Inspect the synchroscope (114, figure 5-1)  for  loose  electrical  connections  and  damaged  or scratched glass. b.  Testing. (1) Connect the synchroscope as shown in figure 5-17  test  setup.    Frequency  generators  used should  be  capable  of  providing  minimum  50 volts, maximum 240 volts.  Frequency 0 to 60 Hz.  For testing the pull-in frequency is 48 Hz, the drop-out frequency is 47 Hz. (2) The   synchroscope   axial   polarizing   coils   are energized    from    the    'incoming'    frequency, while the radial field coils are connected to the 'running'    circuit.    If    there    is    no    difference between the two circuits either in phase angle or frequency, the pointer will remain motionless  at  the  12  o'clock  position  on  the dial.  With no frequency difference, any phase angle difference will cause the pointer to take up    a    position    away    from    this    point.        If, however,  there  is  a  difference  in  frequency, this    phase    relationship    will    be    constantly changing   and   the   pointer   will   consequently rotate   continuously   in   one   direction   or   the other    at    a    speed    corresponding    to    the difference  in  frequency.    If  incoming'  is  at  a higher  speed  than  the  'running',  the  pointer rotates  clockwise,  and  counterclockwise  if  its speed is lower. (3) When   the   lamps   turn   off   together,   the   two sources are synchronized. When the 'incoming'   frequency   has   been   adjusted   to equal   that   of   the   'running'   frequency,   the pointer  will  come  to  rest  at  a  point  on  the scale depending on the phase displacement of the two voltages.  The speed of the 'incoming' must   then   be   inched   up   or   down   until   the pointer takes a steady position at 12 o'clock. c. Replacement.  To remove the synchroscope from the generator panel, tag and disconnect wires, and remove attaching hardware.  Replace in generator panel    with    attaching    hardware    and    reconnect wires.  Remove tags from wires. 5-9.  RESISTOR AND DIODES.  Resistor (26, figure 5- 1, sheet 1) and diodes (25) are all mounted on terminal boards (24) on the rear wall of the enclosure.  They are removed  by  unscrewing  them  from  their  terminals  on terminal boards. a. Test     resistor     (26)     by     measuring     with     an ohmmeter.        It    should    be    39,000    ohms   ±5 percent. b. Test diodes as follows: (1) Disconnect one end of the diode. (2) Connect   an   ohmmeter   (scale.   set   Rx100) across   the   diode,   note   the   reading.      Now reverse   ohmmeter   leads   to   the   diode,   and again  note  reading.    A  good  diode  will  read high  resistance  one  way  and  low  resistance the  other  way.    A  shorted  diode  will  read  full scale  both  ways.    An  open  diode  will  read infinity (no reading) in either direction.  Check all diodes and replace disconnected leads. 5-10.  DIGITAL CLOCK. a. Testing. (1) Connect clock in test setup shown in figure 5-18. (2) Close switch S1 to test 60 5-22