TM 55-4920-401-13&P
Table 4-6.
% RPM Indicator Troubleshooting Table.
Malfunction
Probable Cause
Corrective Action
% R P M i n d i c a t o r c a n n o t b e
a. %RPM indicator out
a. Calibrate.
calibrated with CAL ADJ pot.
of calibration
b. Defective + 7 vdc sup-
b. Repair + 7 vdc supply.
ply cm calibrator board
c. Defective 70 Hz signal
g e n e r a t o r o n c a l i b r a t or
board
d. Defective CAL ADJ pot
or connecting wires
e. Defective A/D con-
verter
c. Repair signal generator
d. Replace pot (65, figure
FO-7)
e. Troubleshoot per para.
4-7C.
Table 4-7. Standard Day Circuit Troubleshooting Table.
Malfunction
S t a n d a r d d a y c i r c u i t c a u s e s e x-
c e s s i v e s h i f t i n t e m p e r a t u r e
and % rpm readings.
A M B T E M P p o t e n t i o m e t e r c i r -
cuit cannot be calibrated.
Probable Cause
a. Standard day circuit
out of calibration
a. Defective AMP TEMP
b. Defective amplifier
A1 on calibrator board
c . O n e o f r e s i s t o rs
R7-R11 on calibrator board
defective
d. Defective 9-volt zener
diode, CR1, on calibrator
board
Corrective Action
a. Calibrate.
a. Replace potentiometer
b. Replace amplifier
(4, figure 4-36)
c. Replace defective resistor.
d. Replace diode (13).
4-9
