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TM 55-4920-412-13&P
i.
Rotor Speed
NOTE
Observe
amplitude
limitations
of
frequency
counter,
unattenuated
inputs can cause damage.
(1)
Connect frequency counter to connector
NO 1 pins A (HI) and B (LOW), using two leads and
adapter.
(2)
Set ROTOR SPEED CAL/NOR switch to
CAL, HI/LO switch to HI and variable control fully CW.
(3)
Set ON-OFF-SIM ONLY switch to SIM
ONLY.
(4)
Measure frequency. Frequency counter
will indicate between 11,245.1 and 11,247.1 Hz. If not,
perform Troubleshooting Table 4-12.
(5)
Set ROTOR SPEED HI/LO switch to LO.
Frequency counter will indicate 0. (Disregard residual
noise count). If not, perform Troubleshooting Table 4-
12.
(6)
Set ROTOR SPEED CAL/NOR to NOR
Frequency counter will indicate between 17,200 and
18,000 Hz.
(7)
Adjust ROTOR SPEED variable control
from fully CW to full CCW. Frequency counter indication
will vary from 0 to 17,200 Hz minimum. If not, perform
Troubleshooting Table 4-12.
(8)
Set ON-OFF-SIM ONLY switch to OFF.
Table 4-12. Troubleshooting Rotor Speed (Hz) (AVIM)
NOTE
Before performing troubleshooting, remove frequency simulator A3 board and
reconnect using extender board.
Trouble
Probable Cause
Remedy
HI-CAL - No Frequency Output
U4 pin 13 (337 Hz t 5 Hz)
First check loops 44(-) and 3(+) for
U8 pin 4, -5 (675 Hz +5)
11,246.1 Hz 1.0 Hz and check U12 pin 7
(HI), U8 pins 4 HI, 5 HL U12 pin 7 HI.
Replace defective components,
Figures 4-8, 4-9, FO-3, FO-5, or replace
A3 board.
LO-CAL indicates
HI/LO Switch (S9)
Replace defective components,
Frequency (Hz) greater than 0 Hz
Figures 4-8, 4-9, FO-3, FO-5, or replace
A3 board.
NOR-FULLY CCW
NOR Control (R4)(R5)(R8) or Q1)
Replace defective components,
Frequency indication greater than 0 Hz
Figures 4-8, 4-9, FO-3, FO-5, or replace
A3 board.
NOR-FULLY CW
NOR Control (R4)Q1, Q6, Q11 or
Replace defective components,
NO Frequency Output
U1A (U1A, C6 or R6 amplitude)
Figures 4-8, 4-9, FO-3, FO-5, or replace
A3 board.
NOR-Frequency indication out of
Trim Resistor R1
Use decade resistor box and check or
tolerance
replace defective components,
Figures 4-8, 4-9, FO-3, FO-5, or replace
A3 board.
4-20 Change 2
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