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JQE SPECIAL SVC 092611
5-5/(5-6 Blank)
to A1CR18, provides the operating voltage for the amplifiers (±15V) and +6.2V reference volt-
age.
PRE-DRIVER POWER SUPPLY.
A full-wave-rectified (A1CR10) and capacitor-filtered (A1C10)
supply is derived from a secondary winding on T202. It delivers supply voltage to the pre-driver
stage A1Q2.
CONSTANT CURRENT RETURN SUPPLY.
This full-wave rectified auxiliary supply is derived
from the winding of the auxiliary power transformer. Rectified by A1CR5 and filtered by A1C5,
constant current is applied to the base of the pass transistors (via the constant current generator
stage A1Q1, thus insuring the control of the Pass-Element for zero output voltage.
5.2.8
METERING CIRCUIT
Both output voltage and output current are monitored by dual range front panel meters (M101,
M102). While the output voltage is measured directly across error sensing terminals 1 (–SENSE)
and 5 (+SENSE) of terminal block TB501, the output current is measured indirectly as a voltage
drop across the current sensing resistor (R203).
5.2.9
MONITORING CIRCUIT
Both output voltage and output current can be remotely monitored through isolated analog sig-
nals available at the MONITOR PORT connector on the rear panel. The 0 to +10V monitor sig-
nals correspond to 0 to +25V for output voltage and 0 to +20A for output current. A1IC5 and
A1IC7 are the isolating amplifiers for the voltage monitoring circuit. A1IC6 and A1IC8 are 2-pole
low-pass filters for the voltage and current monitor signals.
The Voltage Monitor ZERO and FS (full scale) values can be calibrated using potentiometers
A1R45 and A1R39, respectively, accessible through a slot in the top cover. Similarly, potentiom-
eters A1R53 and A1R47 can be used for current monitor calibration. The voltage and current
monitor signal returns are tied together by default, but they can configured to be independent
(isolated) by removing the jumper at test point A1TP1.