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TM 55-4920-412-13&P
j.
Engine % RPM NO 1 and NO 2.
(1)
Connect frequency counter to connector
NO 1 pins C (HI) and D (LOW), using two leads and
adapter.
(2)
Set ENGINE % RPM NO 1 CAL/NOR
switch to CAL. H/LO switch to HI and variable control
fully CW.
(3)
Set ON-OFF-SIM ONLY switch to SIM
ONLY. Frequency counter will indicate between 1,332.5
and 1,334.5 Hz. If not perform Troubleshooting Table
4-13.
(4)
Set ENGINE % RPM NO 1 HI/LO switch
to LO. Frequency counter will indicate 0. If not, perform
Troubleshooting Table 4-13.
(5)
Set ENGINE % RPM NO 1 CAL/NOR to
NOR. Frequency counter will indicate between 1,830
and 2,030 Hz.
(6)
Adjust ENGINE % RPM NO 1 variable
control from fully CW to fully CCW. Frequency counter
will indicate 0 Hz. If not, perform Troubleshooting Table
4-13.
(7)
Set ON-OFF-SIM ONLY switch to OFF.
(8)
Disconnect leads from connector NO 1
pins C (HI) and D (LOW) and connect to connector NO 2
pins Y (HI) and Z (LOW).
(9)
Repeat (2) through (7) above, except use
ENGINE % RPM NO 2 controls.
Table 4-13. Troubleshooting Engine % RPM NO 1 or NO 2 (AVIM)
NOTE
Before performing troubleshooting, remove frequency simulator A3 board and
reconnect using extender board.
Trouble
Probable Cause
Remedy
HI-CAL % RPM indicates No
NO 1 - U5 pin 7 (61,342 Hz 27 Hz)
First check loops 44 (-) and 3 (+)
Frequency Output
U13 pin 7 (61,134 Hz 27 Hz)
NO 1 for 1333.5 Hz 1.0 Hz and check
U15 pin 7 (HI), U14 pin 7 (HI), U13
pin 7 (HI), U5 pin 7 (HI). Figures 4-9,
FO-3, FO-5, or replace A3 board.
LO-CAL
NO 1 - (S11)
Replace defective components A3
Frequency greater than 0 Hz
NO 2- (S13)
board, Figures 4-8, 4-9, FO-3, FO-5,
or replace A3 board.
NOR-FULLY CCW
NO 1 - (R5)(R14)(R17)
Replace defective components A3
Frequency greater than 0 Hz
NO 2 - (R6)(R30)(R27)
board, Figures 4-8, 4-9, FO-3, FO-5,
or replace A3 board.
NOR-FULLY CW
NO 1 - (R5)(Q2),(Q7)(Q12)(U18)
Replace defective components A3
NO Frequency Output
NO 2 - (R5)(Q3)(Q8)(Q13)(U2A)
board, Figures 4-8, 4-9, FO-3, FO-5,
or replace A3 board.
NOR-Frequency out of tolerance
Trim Resistor
Replace defective components A3
Frequency greater than 0 Hz
NO 1 - (R4)
board, Figures 4-8, 4-9, FO- 3, FO-5,
NO 2 - (R23)
or replace A3 board.
Frequency out of tolerance after
NO 1 - (R3)(C4)(Q7)(R18)
Replace defective components A3
trim resistors checked or replaced
NO 2 - (R24)(C13)(Q8)(R31)
board, Figures 4-8, 4-9, FO-3, FO-5,
or replace A3 board.
Low Amplitude effecting Frequency
NO 1 - (U18)(C7)(R15)
Replace defective components A3
NO 2 - (U2A)(C18)(R28)
board, Figures 4-8, 4-9, FO-3, FO-5,
or replace A3 board.
Change 2 4-21
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