TM5-6115-593-34 NAVFAC P-8-631-34 TO-35C2-3-463-2 (1) Remove  and  tag  wires  to  terminals  1 through 6 on the terminal board. (2) Remove  four  screws  (1  and  3,  figure 4-10) from each unit. (3) Replace motor-operated potentio- meter P4 or P5 on shelf by attaching four screws (1 and 3, figure 4-10). (4) Connect  wires  to  terminals  1  through 6 on terminal board. Remove tags. b. Test.        The    following    testing    procedure applies   to   both   motor   operated   potentio- meters     P4     and     P5,     unless     otherwise indicated. (1) Test chassis isolation with an ohmmeter    (set    on    high    scale)    by measuring between chassis and terminals 1 through 6 on the terminal board.    Meter  reading  should  be  no continuity. (2) Referring to figure 4-16, provide a test setup as follows: (a) Connect  the   (-)   of   a   24V   DC source  to  terminal  6.    The  (+) side   of   the   center   terminal   of SPST switch as shown. (b) Label switch RAISE and LOWER.    Connect  the  RAISE terminal    of    SPDT    switch    to terminal    5    and    the    LOWER terminal    of    SPDT    switch    to terminal 4. (c) Connect  an  ohmmeter  between terminals 2 and 3. (d) Turn   24V   DC   power   on.   Set SPDT  switch  to  RAISE.    Meter shall read 230 ±5 ohms connected  between  terminals  2 and 3. (e) Set   SPDT   switch   to   LOWER. Meter   shall   read   8   ±5   ohms connected  between  terminals  2 and 3. NOTE If ohmmeter readings at steps (d) and (e) are incorrect, cams need adjustment. (f) The 230 ±5 ohm reading in step (d) is adjusted with cam B.  This cam should be adjusted to stop the  motor  at  230 ±5  ohms,  see figure 4-17. (g) The  8  ±5  ohm  reading  in  step (e) is adjusted with cam A.  This cam should be adjusted to stop the  motor  at  8  ±5  ohms,  see figure 4-17. NOTE Potentiometer  reading  adjustments  in steps (f) and (g) are for motor-operated potentiometer   P5.      For   P4,   readings are  500 ±5  ohms  in  step  (f),  and  1  ±5 ohms in step (g). (h) Verify that the motor can be run at   1   rpm   to   3   rpm   as   R3   is rotated from clockwise to counterclockwise. Leave R3 set for 3 rpm operation. c. Repair.        Components   within   the   motor- operated potentiometers that may be repaired  are:  brush  replacement  in  motor M1, tightening of set screws on gears, cam adjustments and clutch torque. (1) When    motor    M1    (9,    figure    4-15) brushes are worn under 0.25 inch (6.4 mm) long, they must be replaced. (2) Remove  cover  (3)  by  moving  three screws  (1)  and  washers  (2).    Tighten setscrews (19) on gear assembly (20) and setscrews (28) on gear (29). (3) Adjust  cams  A  and  B  in  accordance with procedure in paragraph 4-26b (f) and (g). (a) With cover (3) removed, remove   motor   mounting   plate (17) and motor (9) by removing two screws (8). 4-26