B I A S S U P P L I E S P R O B L E M - Agilent Technologies E3633A Service Manual

Chapter 5 Service
Troubleshooting Hints
Bias Supplies Problems
C h e c k t h a t t h e i n p u t t o t h e v o l t a g e r e g u l a t o r s o f t h e b i a s s u p p l i e s i s a t l e a s t
1 V g r e a t e r t h a n t h e i r o u t p u t .
C i r c u i t f a i l u r e s c a n c a u s e h e a v y l o a d s o f t h e b i a s s u p p l i e s w h i c h m a y p u l l d o w n
t h e r e g u l a t o r o u t p u t v o l t a g e s .
C h e c k t h e v o l t a g e s o f b i a s s u p p l i e s a s t a b u l a t e d b e l o w .
Table 5-1. Bias Supplies Voltages
Bias Supply Minimum
+5V Floating
-5.1V Floating
+15V Floating
-15V Floating
S o m e c i r c u i t s p r o d u c e t h e i r o w n l o c a l b i a s s u p p l i e s f r o m t h e m a i n b i a s
s u p p l i e s . B e s u r e t o c h e c k t h a t t h e s e l o c a l b i a s s u p p l i e s a r e a c t i v e . I n p a r t i c u l a r ,
t h e A D C ( a n a l o g - t o - d i g i t a l c o n v e r t e r ) , a c i n p u t , a n d f r o n t p a n e l s e c t i o n s h a v e
l o c a l b i a s s u p p l i e s . A l w a y s c h e c k t h a t t h e p o w e r s u p p l i e s a r e f r e e o f a c
o s c i l l a t i o n s u s i n g a n o s c i l l o s c o p e . F a i l u r e o f b i a s s u p p l i e s w i l l c a u s e m a n y s e l f -
t e s t f a i l u r e s .
Maximum
+4.75 V +5.25 V
-4.75 V -5.25 V
+14.25 V +15.75 V
-14.25 V -15.75 V
Check At
U10 pin 2
Anode of CR6
Anode of CR9
Cathode of CR10
5
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