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M o d e l 5363 B
S ervice
A1 M O TH E R B OA R D A S S E M B LY (Sheet
M u c h of the c i rc u i t ry s h o w n I n s h e e t 2 of
probes before s e n d I n g the m to t h e rea r p a n e l J a c k s . Exc
s c h e m a t i c c a n b e d i v ided In halt with t h e upper h a l t b e i n g the s t a rt c h a n n e l and t h e bottom half
being t h e stop c h a n n e l T h e t e x t will refer to t h e s t a rt c h a n n e l
S i n c e e i t h e r A probe or B p r o b e c a n r e c e i v e t h e start s i g n a l , t h e i n v e r t i n g a n d n o n i n v e r t l n g
o u t p u t s from t h e A a n d B p r o b e "start" FETs e n t e r A 1 a n d f e e d U 2 4 a n d U 2 7 : U24 c o n t r o l s
c h a n n e l A a n d U 2 7 c o n t r o l s c h a n n e l B
selected a s the start c h a n n e l b y t h e t h u m b w h e e l s W i t c h T h e p u rpose of t h e s e I Cs I S t o s W i tc h
t h e i n v e rt i n g a n d n o n i n v e rt l n g s i g n a l s t h a t g o to c o m parator U 1 8 B . T h e S T A R T S L O P E a n d
S T A R T S L O P E l i n e s c o m e f r o m t h e state m a c h i n e , b u t t h e i r states a re a c t u a l l y a re s u l t o f t h e
s l o pe t h u m b w h e e l T h e s e l i n e s c o n trol t h e s t a t e of 0 1 6 a n d 0 1 5 , w h i c h , i n t u r n , c o n t r o l t h e
t ra n s i s tors w i t h i n U 2 4
A s s u m e t h e t h u m b w h e e l l s set for I h e p o s i t i ve s l o p e T h e S TA R T S L O P E l i n e is h i g h a n d the
START S L O P E l i n e I S low. T h i S t u rn s
U24: 8 : a n d a low , � 1 1 .5 V , o n U24, 4 : . ThiS a
to the negative I n p u t of U 1 8 B a n d t h e n o n l n ve r t l n g s i g n a l t h ro u g h U 2 4 0 1 t o t h e pos i t i ve i n pu t
of U 1 8 B U 1 9 B g i ves t h e s i g n a l a f a s t e r r i s e t i m e b e f o r e 0 1 3 a n d
:+: 1 V f o r t h e re a r p a n e l S T A R T l a c k : o u t p u t t o c o u n te r : .
T h e s t o p portion o f t h e s c h e m a t i c I S s i m i l a r, w i t h t h e e x c e p t i o n o f t h e d e l a y c i r c u i t ry. W h e n t h e
front p a n e l P U L L TO A D D 1 0 0 n s s W i t c h i s p u l led o u t , I t a c t i va t e s r e l a y K 1 t h r o u g h 0 5 T h e
r e l a y a d d s a 1 0 n s d e l a y l i n e i n series w i t h t h e s i g n a l before t h e s i g n a l e X i t s t h r o u g h the rear
panel STOP Jack. T h e front panel pot c a n perform a fine a d j u s t m e n t t o c o m p e n s a t e t o r probe
and system time delay d i fferences. ThiS IS d o n e b y va r y i n g t h e vo l t a g e a c ross varactor C R 1 6
Probe Turnoff
Each probe c o n t a i n s a " s t a r t " p a i r o f FETs and a "sto p " p a i r O n l y one s t a rt and one stop p a i r
c a n b e a c t i ve a t a t i m e , T h e start a n d s t o p F E T p a i rs t h a t a re n o t selected m u st b e t u r n ed off
This I S done t h r o u g h 0 2 , 03, 0 4 , and 0 6 : f or t h e start c h a n n e l and 0 1 7 , 0 1 8 , 0 1 9 , and 020 for
CHAN
t h e stop channel
START
l i n e to g o to - 1 5 V , w h i c h t u r n s o n t h e A p r o b e start C i rC U I t . T h e B P R O B E - 1 5 V START l i n e
rests a t OV a n d keeps t h e
Power Supply
T h e po wer s u p p l y C i r C U i t c o n t a i n s five f i xed r e g u l a t o r s . U4 f o r 1 2 0 V , U1 f o r - 1 5 V , U2 f o r +5V,
U 3 for + 1 5 V , a n d U 5 f o r +9.8V. U 5 s u b t racts 5.2V from t h e 1 5 V s u p p l y to g i ve ·1 9 . 8 V C l a m p
d i o d es C R 6 a n d C R 26 protect t h e c o m p a rators f r o m d a m a g e s h o u l d a fa i l u re o c c u r I n o n e of
the s u p p l ies I h a t feed the c o m parator. If one of the s u p p l i e s b e c o m e a c c i d e n t l y s h o rted to
g ro u n d , for exa m p l e , t h e o t h e r s u p p l y w i l l s h u t d o w n t o prevent d a m a g e .
' e xercised to avoid accidental shorting of pins of these ICs'\o
8-58
O t 6
A ss u m e A c h a n n e l h a s b e e n selected t o detect a start. I n this case, t h e
l i n e I S h i g h a n d START C H A N I S l o w . T h i s c a uses t h e A P R O B E - 1 5 V S T A R T
8
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Figure 8 - 1 1
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ud I n g t h e po we r s u ppl y c i rc u i t r y , the
I
o n l y o n e of these I Cs w i l l b e a c t i ve at a t i m e : t h e o n e
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