Figure 1-21. % RPM Signal Flow Diagram.

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