Relationship - HP 333A Operating And Service Manual

Section
IV
Model 333A/334
4-33.
Refer to Figure
4-5 for the phase relationship
o f the bridge error signal andreference voltage
at the
base of
A5Q4. The shaded portions of
the e r r o r
sig-
nals ( b a n d c) indicate that part of the e r r o r signal
which contributes to the dc lamp control voltage. As
indicatedind, any e r r o r signal that ie 90° outofphase
with
the
reference does not affect the dc lamp control
voltage, because equal
amounts
of the positive and
negative portions
are passed.
4-34. The operation d the reactive branch control
loop ie similar to that of
the
resistive branch. The
phase delay circuit, A5Q15, A5Q16, S4AF and
S4C1 through S4C5, shifts the reference voltagc
90°,
aa
shown
in
Figure 4-5f. This makes the detector
A5Ql2 sensitive to components of the bridge e r r o r
signal that are 900 out of phase (g and h). The outpui
of the
lamp driver, A5Q14, controls the brilliance of
A6DS2, which varies the resietance of A6V2 through
A6V5 to tune the branches of the reactive leg. Deck
AR
of the FREQUENCY RANGE switch,
54,
switches
A5R56
in parallel
with A5R55 on the
top three fre-
quency
ranges.
A6DS2 w i l l become brighter, and lower
the resistance of A6V2 through A6V5, makingvariatio
45' 135' 225' 315'
a
Ref. signalfor Resistive
Detector (A564)
b
Resistive Error
signal
in phase w i t h reference
a t bridge
Resptive
Error signal
180 out of phase
d
Reactive Error
signal
30 out of phase (Results
in no output from Re-
sistive Detector)
e
Error
signal, reactive
leg detuned, resistive
.eg unbalanced
f
Ref. signal
for Reactive
Detector (A56 12 b
Reactive Error signal
in phase with reference
at
bridge
Reactive Error
out o f phase
h
signal
i
R e p t i v e Error
signal
90 out of phase(Results
in
no output from Re-
active Detector)
Error
signal,
Reactive
leg detuned, Resistive
leg unbalanced
45'
13s' 225' 316'
Figure 4-5. Reference and
Error
Phase Relationship
4-4