a. External metering circuit.
This circuit includes EXTERNAL METER SELECT switch S2 and EXTERNAL
METER jacks J4 and J5. The switch selects one of four voltages. At VALVE, the valve drive signal is selected. At
CROSS FDBK, the cross signal is selected, At SELF FDBK, the self signal is selected. At REF, the 13 volts ac
reference voltage is selected. The selected signal is applied to the jacks, At the jack, it can be measured with ex-
ternal test equipment.
b. DVM metering circuit. (fig. 1-6).
(1) The DVM has an auto range circuit on TB6B to protect the meter from high voltage surges.
(2) The DVM voltages are selected by SYSTEM SELECT switch S3 and LINK TEST switch S7 or S9.
(3) The DVM is connected to SYSTEM SELECT switch S3. S3 selects BITE, SAS 1, or SAS 2 voltages to
be read by the DVM. The voltages going to S3 (SAS 1 or SAS 2) are selected by the LINK TEST switch S7 or
S9. S7, like S9, can select VALVE, CROSS FEEDBACK or SELF FEEDBACK.
(4) The auto range circuit will then automatically range the selected voltages to be read by the DVM.
c. NULL meter circuit..
(1) This circuit includes FEEDBACK SELECT switch S13 and S15, R28 and R29 in PCA 1 and PCA 2,
METER X10 switch S4 and S6, and NULL meter Ml and M2.
(2) FEEDBACK SELECT switch selects SELF or CROSS output current. METER X10 switch when
pressed connects R29 in parallel with R28 changing the NULL METER range to 5 microamps maximum from
(3) When METER X10 switch S4 or S6 is not pressed, all current goes through R28. The range of NULL
METER Ml or M2 is 50 microamps maximum right or left of center,
(4) Do not press METER X10 switch when reading more than 5 microamps.
1-19. Power Circuits (fig. 1-7),
a. The 115 volts ac 60 Hz is applied through POWER receptacle J8 and circuit breaker S17 to terminal board
TB5. The ac is distributed to the power supplies, undervoltage detector circuit, and the hydraulic unit control cir-
b. Power supply PS2 provides 28 volts dc. The dc lights the indicators, provides an input to inverter PS3, and
drives the elapsed time indicator.
c. The dc is applied to inverter PS3. Inverter PS3 provides 26 volts ac 400 Hz output to T1. The output of
transformer T1 is a 13 volts ac 400 Hz reference signal.