HP 333A, Technical Manual

Page: 23 / 53

TM 11-6625-1576-15
model 333A/334A
Section IV
Paragraphs 4-46 to 4-52 and Figure 4-8
Figure 4-8. Simplified Metering Circuit
4-46. POWER SUPPLY CIRCUIT.
4-47. The power supply circuit (refer to Figure 6-5)
consists of a +25 voIt series regulated supply and a
-25 volt series regulated supply which is the reference
supply for the +25 volt supply.
4-48. The -25 volt regulated supply is of the conven-
tional series regulator type. The amplifier A1Q5 is
used to increase the loop gain of the circuit, thus im-
proving voltage regulation. The positive feedback ap-
plied to the junction of A1R1l and A1R12 is used to
further improve the line frequency suppression of the
circuit.
4-49. The +25 volt regulated supply is of the conven-
tional series regulator type and operates the same as
the -25 volt regulated supply.
4-50. Diodes A1CR5 and A1CR6 are coupling and pro-
tection diodes for external battery supplies. The diodes
protect the series regulator circuits from application
of incorrect polarity at the battery input terminals.
The diodes also protect external batteries from being
charged when the ac power is being used with batteries
connected to the battery terminals.
4-51. RF DETECTOR CIRCUIT. (334A only)
4-52. The RF detector circuit consists of a rectifier
A4CR1 and filter circuit shown on the schematic dia-
gram of Figure 6-2.
The RF signal is applied to the
circuit through the RF INPUT connector on the rear
panel. The rectifier diode A4CR1 recovers the modu-
lating signal from the RF carrier and the filter circuit
removes any RF components before the signal is ap -
pIied to the impedance converter circuit through the
NORM -RF DET switch, S7.
4-7