HP 3490A - Page 192

Remov€
413U3.
Set
FIA-
TIO sitch
to EXT REF
l0V. Disconnect dc
atan-
dard
from
INPUT
and
@6-
net
to EXT
REF t6m.
Monitor
voltage 4
Al3
t6t
point
C
whils applying
EXT
REF bltäges
below:
EXT REF TPC
+
20
V
+
'13.6
to
+
14.3 V
-20
V
-
13.6 to
-
14.3 V
Replace A13U3
in
$cker,
Disconned
dc sbndard
from
EXT
REF and con-
nEt to
INPUT terminals.
Apply
-
10.0000
V.
Select
TEST
4. Short EXT
REF
tfrmiEls.
With RATIO
set
to EXT
REF 10 V,
display
should be 00.0000 t.
Perform Ratio Adjust-
ren$, Parag.aph
5-79.
Chrck Inpur Prottrtion
Circuit Al3CRl-4,
A13Fl1-3. Aft* rep6ir,
go
to nexl step.
Disonnect
front
penel
6-
ble
W8 fJom
Ratio
Asem-
bly 413.
Ground
pin
2 of
l E @nnector
on A'13. Re-
mve 413U2.
Connect dc
sbndard
to A13TPC and
monitor voltage
at @thode
ol
Al3CR6 while
applying
|to
v:
TPC
A13CR6
+10V +l2.9to+14.3V
-
10 V
-
12.9
to
-
'14.3
V
Refer to
G6eäl Trouble-
s*rooting
Tree, Fig.7.4,
min 34904 man@l-
Check A13CR6,7
and re-
place
if deffttiw- lf diodes
a.e
good,
replace
Al3U1
with new
Frt.
After re-
parr, go
to next step.
YES
Wirh €ble W8 dis@nnected,
pin
2
of c
grourded,
and U2 removed,
set
FUNCTIO
FANGE to 1o V. Apply any
INPUT vol
polaritv
lhown b€low,
and apply
t
10!
c'hecking logic lewls
as sh@n:
(Note
2,
INPUT
+
+
TPC
f
t0 v
+
10 v
-
10
v
-10v
u5{121
HIGH
LOW
LOW
HIGH
TPD
LOW
LOW
HIGH
HIGH
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