TM 55-4920-401-13&P
(5) % RPM Signal Circuits. The % rpm sig-
oscillator with a frequency of 455K Hz. Binary
nal circuits are shown in figure 1-21. The % RPM in-
counters BC1 and BC2 and gates G1A,B and G2A di-
dicator calibration signal generator is on the cali-
vide the frequency by 3250 to 140 Hz and FF1 di-
brator board in the trimmer. The circuitry of crystal
vides the frequency by 2 to 70 Hz.
XT1 and gates G2B, C, D forms a crystal controlled
Figure 1-21.
% RPM Signal Flow Diagram.
( 6 ) S t a n d a r d D a y C o r r e c t i o n C i r c u i t-
switch-power board. Q16 drives the STD DAY lamp
ry. The standard day circuit, when activated, cor-
when the STD DAY switch is on. When all above
rects temperature and % rpm readings to standard
named switches are in the proper position, Q17
day conditions during engine trim. To activate the
turns on Q16. The STD DAY lamp burns con-
circuitry, set ambient temperature on the AMB
tinuously. If a switch is “out-of-position”, the base
TEMP potentiometer, turn the FUNCTION SE-
circuit of Q18 is returned to ground through the
LECT switch to TRIM, the TEMPERATURE switch
switch. Q18 turns on, turning off Q17 and Q16. C12
to OPERATE, the RPM switch to N1 or N2, and the
and C13 charge until the emitter-base junction of
STD DAY lamp burns continuously if the other
Q17 becomes forward biased, at which point Q17
switches are in their correct positions. If one or
and Q16 turn on again.
more of the other switches named above are not “in
(b) Standard Day Equations. S t a n d a rd
position”, the STD DAY lamp flashes.
day corrections are made according to the following
(a) STD DAY lamp Circuit. The circuitry
equations:
that controls the STD DAY lamp is located on the
Corrected temperature (°C) = uncorrected temperature (°C) + 273
0
-273, Corrected percent rpm = uncorrected percent rpm;
0
where 0 = observed ambient temperature (°F) + 460
519
or 0 = observed ambient temperature (ºC) + 273
288
1-20
