Section V
Paragraphs
_
i.
Establish an output reference on the
test
o s
‑
cillator using the OUTPUT MONITOR E X
‑
PAND
switch and
REF SET controls.
j.
Increase oscillator. frequency to
1 m c .
R e
‑
adjust oscillator amplitude to maintain
set
reference.
k.
AdjustC2
(0.3
V 1
M C ) f o r a 0.3 V indication
o n
the M o d e l
403A.
m. Connect
test
setup
shown
in F i g u r e
5-11.
OSCILLATOR MONITOR
AC VOLTMETER
hp 400E
4 0 3 A - B - 11 0 3
F i g u r e
5-11.
30 V Range
200
kc Adjustment
n .
Set
Model
403A RANGE t o 3 0 V. Set o s c i l
‑
l a t o r
frequency
to
200 k c .
Adjust
oscillator
amplitudefor a r e a d i n g
of 10 V or
greater on
the
oscillator
m o n i t o r.
p. Adjust C4
(30
V
200 KC) f o r a
Model
403A
reading the
same as the oscillator monitor
reading.
5 - 3 1 . T R O U B L E S H O O T I N G .
5-32. T h i s section contains information designed to
assist
in
isolating
malfunctions in the Model 403A.
Troubleshooting should be
undertaken only after it
has
beendefinitely established
t h a t the
trouble
cannot
be eliminated by performing the
adjustment
and
c a l i
‑
bration procedure
(Paragraph 5-19).
5-33.
Conduct a
visual check
of
the Model
403A f o r
possible burned or
loose components, loose c o n n e c
‑
tions,
or
other obvious conditions
which m i g h t
suggest
a source of trouble.
5-34.
Weak batteries can cause
e r r a t i c
instrument
operation. Before troubleshooting, a new
set
of b a t
‑
t e r i e s
should be installed.
5-35. Table
5-3
containsa
summary
of several
m a l
‑
function
symptoms
and t h e i r possible
causes.
T h i s
table canbe used
t o
selecta
s t a r t i n g p o i n t
f o r
t r o u b l e
‑
shooting
operations.
5-6
~
o * .
M o d e l
403A
Ta b l e
5-3.
Troubleshooting
No response to input
Fuse F1 blown
Batteries dead
CR1 or
CR2 shorted
Open
contacts in
range
switch
B a t t e r y
Te s t reads
Weak batteries
low
One or m o r e batteries
installed backwards
B a t t e r y
Te s t
C a l
(R47)
not set
p r o p e r l y
Noisy
indication on
D i r t y b a t t e r y
contacts
known quiet
source
CR1 or CR2
noisy
Noisy transistors
(usually Q1 or
Q2)
M e t e r
pegs
when
D i r t y
contacts on
range
s w i t c h i n g r a n g e s s w i t c h
C10
or
C15
leaky
M e t e r
pulsates
when
C21, C22, C25,
C26
measuring
inputs
C31
or
C32
open
or
less
than
15 cps
leaky
M e t e r calibration o ff | B a d r e s i s t o r in
range
on ranges
t h a t a r e
s w i t c h
multiples of
100
D i r t y
contacts
in
range
apart
switch
R44 (METER
C A L
Weak batteries
10 MV RANGE)
CR3,
CR4 bad
w i l l
not
adjust
Input
resistance
out
Q1 or Q2
b a d
of spec
M e t e r
does
not
track
p r o p e r l y :
a . M e t e r reads
con- | R32 b a d
s i s t e n t l y
above o r
below
a l l
meter
divisions
M e t e r
reads
above
|
CR3,
CR4
b a d
some
b u t
below
M e t e r b a d
other divisions
5 - 3 6 .
REPAIR.
5-37.
CABINET REMOVAL.
a.
Remove the
f o u r
screws
at the r e a r of
the
cabinet.
b .
C a r e f u l l y
slide
the
Model
403A
f o r w a r d ,
out
of
the
cabinet.
A LWAY S REMOVE BATTERIES
BEFORE
REPLACING
ANY PARTS.
A LW AY S T U R N
MODEL 403A
O F F
B E F O R E
REMOVINGBATTERIES.
00125-4
