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HP 8110Α Se
r
vice G
u
ide
S
L
A
VE
IC Slope Switc
h
ing
4-2 2
T
r
oubles
h
ooti
n
g
C
heck
t
h at d i fferential inpu t signal s are a v ail able at pin s 4Η
a
nd 5 Η
on
U
200, t h e S LAVE IC.
If t here are
p
ro blem s with t he sl ope ran ge settings, select
f
aulty
ranges an d ch eck t hat the appropriate tra n sistors are s witch ed on.
You can also ch eck
t
he capacitors. Ho w e ver, ranges 1 an d 2 cannot
be ch eck ed in t his w ay.
Th e ran ges are s wi tched as
f
o llows :
R
an ge 1
Inter n al capacitor s witche d ins ide
U
200
R
an ge 2
Inter n al capaci tor +
p
arasitic capacitance s wi tc hed
insi de
U
200
A s t he ran ges are increased, the external capaci tors are switched by
t
he tran si stors, addin g to the
p
revious cap acity:
R
ange 3
Q200 adds C212 and C213
R
ange 4
Q201 adds C214
R
an ge 5
Q202 A addsc215
R
an ge 6
Q202 B addsc215
R
a n ge 7
Q202C addsc215
R
an ge 8
R
e l ay Κ220 adds t he capacitance mul tipli er circuit,
Current Source
Current Sin
k
U
220
Whe n α tran sistor i s switched O FF th e sl ope app ears at
i
ts collector .
Whe n t he relay i s open
t
he sl op e appears at Κ220 pin 1 .
U
se t he
Sco p e to check , as th ese are h igh imp edance
p
oints.
When α tran sistor is switched on, 0 V
a
pp ears at t he coll ector an d
f
or t he relay , at Κ 220 pin 1 .
Slope Control
Thi s co n s i sts o f two sect ions :
1 . Select vari ou s Slo pe sett ings on the in strument an d check that
v oltages are available
f
ro m U 250 pin 1 (high imp edan ce) and
U 252A pin 1
2 . C heck t h at U254 D pin 14,
U
253D pin 14 a n d
U
253C pin 8 mirror
changes in U252 A pin 1 voltage. Check Q250, Q251 and Q252
1 . Se lect var i ou s Slope sett ings on the instr ument and ch eck th at
v oltages are a vail abl e from U 251 pin 1 (hi gh imp eda nce) and
U252 D pin 14
2 . Chec k t hat
U
254A pin 1,
U
253A pin 1 and
U
253 B pin 7 mirror
cha nges in U 252D pin 14 voltage. C heck Q253, Q254 and Q255
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