Magnetic Instrumentation 942B, Instruction Manual

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Timing sequence:
Provided the timers are enabled, (Pin 10 of header connector at
+
15V), a low (Ov)
applied to Pin 19 of header connector turns off Q301 allowing C303 to discharge. This
starts timers IC301 and IC 302. IC301 turns on Q304 disabling the charge circuit through
Q310, and maintains the low at Pin 12 of header connector. IC301 also turns on Q305
activating the first half of a two transistor “AND” circuit. IC301’s output Pin 3 will
remain active (
+
15V) for the entire discharge cycle. This time is adjustable by the RC
time constant of C301 220µfd, R307 10K, and potentiometer POT301. This timer
remaining active is what provides the delay between the discharge of the machine and the
ability to recharge for the next cycle. Timer IC302 is used to provide a delay between the
start of the discharge cycle and actual discharge of the capacitor banks to allow the charge
circuit enough time to shut-off (approx.: 100ms). When IC302’s output returns to a low
(timing cycle completed) C306 discharges and provides a trigger to IC303. Upon seeing
the trigger the output of IC303 goes high (+15V) and turns on the second half of the
“AND” circuit Q306. This allows the collector of Q305 to go low providing a low
impedance path to ground (supply common) to be seen at Pin 2 of the header connector.
Pin 2 of the header provides the start signal used to trigger the circuit board that drives the
discharge device (typically an SCR driver board).
C. General Description Power Supply and Relay Board # 10401433
This board is a combination of two boards that can be separated from one another. When
not separated, the board is part number 10401433. Once separated the two boards become
a # 10401415 and # 10401416. All references to the header connector pin numbers of #
10401415 should be considered 1CN, and all references to the header connector pin
numbers of 10401416 should be considered 2CN.
D. General Description of ± 15VDC/ ± 24VDC Power Supply # 10401415
To provide normal operation for this board an external transformer (36 VAC center-
tapped) must be used. This board is used to supply unregulated ±24 VDC and regulated
±15 VDC. The +15 output is adjustable from approximately 6.5 VDC to 16 VDC and
must be adjusted prior to use. The -15 output is not adjustable.