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(3) Examine the following l i s t t o determine
your symptom, then c h e c k t h e probable c a u s e .
Symptom
Probable C a u s e
Low output or n o output Insure t h a t the front
voltage
panel meter is not defec-
tive, then refer t o para-
graph 5-57.
High output v o l t a g e
Insure t h a t the front
panel meter is not defec-
tive, then refer t o para-
graph 5-57.
CAUTION
Never s e t t h e output voltage controls
t o z e r o v o l t s when there is high or
low output voltage; damage t o t h e volt-
a g e c o n t r o l s c o u l d result.
Erratic output voltage.
Same a s low output symp-
'$he n e e d l e on the out-
tom; refer t o paragraph
put voltage meter waiv- 5-57.
e r s slightly, or a n o s -
c i l l o s c o p e connected t o
t h e output d i s p l a y s er-
r a t i c ripple.
)
Inability t o r e a c h z e r o
a .
Output voltage con-
output voltage *200
trol R200 defective.
millivolts.
b.
Amplifier Q1 defec-
tive.
O s c i l l a t e s
Slow drift
C20, R20, C l l , R25de-
fective.
a.
Measuring e q u i p m e n t
b.
Reference diode VR1.
c .
Q16
d.
Insufficient warm-up
time (should b e 30 min-
u t e s ) .
Random i n s t a b i l i t y
High voltage control
a.
Large output volt-
c i r c u i t defective.
Refer
a g e t r a n s i e n t s (output
t o Table 5-3 s t e p 8
reductions of 1V or
more)
b.
Large output volt-
High voltage control
a g e t r a n s i e n t s (output
c i r c u i t defective.
Refer
i n c r e a s e s of 1V or
t o Table 5-4, s t e p 6.
more).
c .
Small output volt-
VR1 defective, voltage
a g e t r a n s i e n t s (output
thumbwheel s w i t c h e s
c h a n g e s o f 10-30mV).
noisy, 1Vthumbwheel
control R200 noisy
High Ripple
a.
Check operating set-
up for ground loops.
b.
If output floating,
c o n n e c t lpf capacitor
between output and
ground
c .
Check for e x c e s s i v e
internal ripple; refer t o
Table 5-2.
d.
Ensure t h a t supply
is
not current limiting under
loaded conditions.
Check t h a t t e s t point
(40) is approx. t12V.
Current limit circuit de-
fective or misadjusted
(refer t o paragraph 5-68)
Poor Transient Recov-
C20, R20, C11, R25 de-
e r y Time
fective.
Output Voltage In-
a .
S e t output voltage
a c c u r a c y
controls to 3000V. Out-
put voltage should read
3000V *40V; if not, per-
form adjustment given
in paragraph 5-66.
b.
Slowly rotate e a c h
thumbwheel switch a
s t e p a t a time, and rec-
ord the output voltage.
The s t e p c h a n g e s should
b e within *I%.
A
deviation in a n y s t e p
i n d i c a t e s that the a s s o -
c i a t e d r e s i s t o r is defec-
tive.
5-57
Regulatinq Loop Troubles.
If the v o l t a g e s
in Table 5-2 have b e e n c h e c k e d to eliminate the
reference, b i a s and rectifier c i r c u i t s a s a source
of trouble; the malfunction is c a u s e d b y either
the low or high voltage regulating loops.
If a n y
component in a feedback loop
is
defective, meas-
urements made anywhere in the loop may appear
abnormal.
Under t h e s e circumstances it i s very
difficult t o s e p a r a t e c a u s e from effect with the
loop c l o s e d . As described in Tables 5-3 and
5-4, the trouble is i s o l a t e d t o either t h e high or
low voltage regulating loop.
The loop is opened,
and the conduction and cutoff capability of e a c h
s t a g e is checked a s follows:
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