Keithley 153, Инструкция по эксплуатации, Страница: 26 / 51

SERVICING
MODEL
1 5 3
MI C ROVOLT - AMMETER
mod u l a t ed t ub e t e s t e r f or
u
s
u
a l op e ra t i on . Howeve r ,
sub s t i tu t ing
kn own g o od
t ub e s
i s
t h e
b e s t wa y t o
t e s t
a t ub e .
I f
r e p l a c i ng a t ub e d o e s n o t c o r r e c t t h e t r o u b l e , c o n t i n u e t h e
p r o c e d u re s . R e p
l
a c i
n
g
t ub e s
d o e s n o t n e c e s s i t a t e c omp l e t e r e c a l ib ra t i on o f t h e i n s t ru m e n t .
Re f e r t o T a b
l
e
3
f or a d j u s t m en t s wh i c h m i g h t b e
n e c e s s a ry .
c .
Tab l e 4
c on t a i n s t h e mo r e c ommon t r o u b l e s wh i c h m i g h t o c c u r
.
I f
t h e r e p a i r s i nd i ­
c a t e d i n
t h e
Tab l e
d o
n o t c
l
e a r u p t h e t r oub l e ,
ma k e a
p O in t - b y - p o i n t c h e c k o f t h e c i r ­
c U i t s .
S t a r t
b y
r e c he c k ing t
h
e powe r s u p p l y
f o r
p r o p e r o p e r a t ing v o l t ag e s : + 2 7 5 vo l t s ,
+ 1 50
v
o l
t
s ,
and - 1 3 v o l t s . Figur e s 10
t o 1 2 s how t y p i c a l r ipp l e a t t h r e e t e s t p
o
i n t s
wi t h in t h e p owe r s u p p l y .
U s e
t h e Os c i l l o s c op e t o ob t a in t h e p a t t er n s .
d .
Th t
s c h e ma t i c d i a g ra m 1 7 7 7 1 H , f ound
in S e c t i on
8 , c on t a i n s t h e v o l t a g e s a t
s e l e c t e d
p o in t s .
Fo r
t
h e s e va l u e s , m e a s u
r
e d wi t h t h e Mod e l
6 1 0 B t o
! 10 % , t h e Mod e l
1 5 3
i n p u t i s
shor t ed .
Th e Mod e l
1 5 3 contro l s
a r e s e t :
MET ER S'\o)i t c h
FUNCTION
Swi t c h
RANGE Sw i t ch
+
VOLT S R- 2M
I
VOLT
Re f e r t o t h e c i rc u i t d e s c r i p t i on i n S e c t i o n
4
t o f in d t h e more c r u c i a l c omp on en t s a n d t o
d e t e rmi n e t h e i r fun c t i o n
in t he
c i r cu i t .
F IGURE
10 .
Wave
F
o r
m
a t Jun c t i on o f
Diodes
030 1 and 030 2
( F igure 27) . V
e
r t
i
c
a
l
s e t t ing
is 1
v / cm;
h o r i z on t a l ,
2
m s / cm.
Output i s app rox ima t e l y
+4UU
vo l t s
dc .
FIGURE 1 1 .
Wave Form a t Junc ti on
o f
Resis­
tor
RJ0 2 (Figure 27)
a n d
Capacitor C30 2B
( Figure 19) .
Vertica l
s e t t ing
is
5 mv / c m ;
h o r i z o n t a l ,
2
m s
/
cm.
Output i s ap p roxima t e l y
+1 2
v
o l
t
s
d c .
FIGURE
12
( Le f t ) . Wave
Form
a t
- 13
V o l t
Supp ly .
Ver t i ca l s e t t ing
i s 20
m v / c m
hor i z on t a l ,
5 m s / cm.
5 - 5 .
BIAS ADJUSTMENT .
C
h
e
c
k
the mechan i c a l me t e r z
e
ro
.
Short
p in
I
o f
t
u b e
V i0 3
t o
ground b y
c onn e c t ing p o i n t
T . p .
(Figure 2 1)
t o g r ound .
S e t
the RANGE
Swi t ch t o
1
VOLT ;
t
he
METER
Swi t c h t o
+ ;
and
the FUNCTION
Swi t c h t o
INPUT R- 2M.
A
d j u s t
the
BIAS ADJ Po t en­
t i ome t e r ,
RI 2 5 ( F igure 20) ,
for
a z er o
m
e
t
e
r
read ing . Re
m
o
v
e
the
s h o r t b e tween
T. p.
and
groun d ;
a d j us t
for e xa c t me t e r z e ro .
5 - 6 .
MULT IV I B RATOR
FREQUENCY
ADJUSTMENT .
a . Remove tub e s
V IO L
and
V I0 3
(
F
i g
u
r e
2D .
Turn t h e MET ER
Swi t c h t o
+
and
t h e
FUNCT IO�
18