TM 55-4920-412-13&P g. Digital Set, BCD (thumb wheel switch) circuit. (1) Set ON-OFF-SIM ONLY to OFF. (2) Connect    test    equipment    as    shown    in Figure 4-1, unit tester connected. (3) Connect  digital  multimeter  leads  to  J2  pin 60 (+) and COM. (4) Set ON-OFF-SIM ONLY to ON. (5) Rotate  DIGITAL  SET  B  C  D  thumbwheel switch   through   each   position   as   listed   in   Table   4-26. Digital   multimeter   will   indicate   voltage   within   the   limit specified,  at  settings  listed  in  Table  4-26.    If  not,  see Troubleshooting Table 4-27. (6) Repeat    techniques    (1)    thru    (5)    above using   connector   J2   pins   60,   62,   63   and   64   for   each check    as    indicated    below.        Indications    will    be    as specified at pins and settings as shown in Table 4-26. h. Rotor Overspeed. Performance Check. (1) Disconnect    lead    from    J2    pin    64    and connect to J6 pin 31 on unit tester. (2) Set   ROTOR   OVERSPEED   127%   switch to ON. (3) Set   ON-OFF-SIM   ONLY   to   ON.      Digital multimeter  will  indicate  between  +4.5  and  +55  vdc.    If not, see Troubleshooting Table 4-27. (4) Set   ROTOR   OVERSPEED   127%   and ON-OFF-SIM ONLY switch to OFF. (5) Disconnect    lead    from    J6    pin    31    and connect to J6 pin 32. (6) Repeat   (2)   thru   (4)   above,   except   use ROTOR OVERSPEED 137% switch. (7) Disconnect    lead    from    J6    pin    32    and connect to J6 pin 33. (8) Repeat   (2)   thru   (4)   above,   except   use ROTOR OVERSPEED 142% switch. (9) Disconnect lead from J6 pin 33. (10) Set ON-OFF-SIM ONLY to OFF. i. Display Update. (1) Connect    test    equipment    as    shown    in Figure 4-17.  Do not disconnect equipment connected in Figure 4-1, unit tester connected. (2) Set DISPLAY UPDATE switch to ON. (3) Set   ON-OFF-SIM   ONLY   switch    to    ON. Oscilloscope  will  indicate  negative  pulses  between  4.0 and   6.0v   and   frequency   counter   will   indicate   between 1300  and  1900  Hz.    If  not,  see  troubleshooting  Table 4-27. (4) Set DISPLAY and ON-OFF ONLY switches to OFF. Table 4-26.  Digital Set B C D Digital Set Thumbwheel J2 Connector Pins Digital Voltmeter Indication (vdc) Settings 60 62 63 64 Min Max 0 0 0 1 x 4.5 5.5 2 x 4.5 5.5 3 x x 4.5 5.5 4 x 4.5 5.5 5 x x 4.5 5.5 6 x x 4.5 5.5 7 x x x 4.5 5.5 8 x 4.5 5.5 9 x x 4.5 5.5 Change 2  4-51