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INSTRUCTION
MiNUAL
DIgItsI Multimeter
Models 172,173
MAINTENANCE
TABLE 6-13
(Con't)
SYMPTOM
e)
One display
bar
missing
on all
digits.
f
f)
One digit
missing.
9)
10,000
digit
missing.
(except
if
reading
is
less
than
10,000
counts)
h)
Function
indicator
off.
i)
Faulty
reading
on R
function.
j)
Faulty
reading
on
Current
function.
AA
Troubleshooting
Hinl
PROBABLE CAUSE
1)
Faulty
connection
2)
I)
2)
1)
2)
between
P3Ol
and
JZOI.
Cathode
driver
cir-
cuitry
faulty.
see
schematic
27404D
Faulty
connection
between
R30l
and
J2Ol.
Anode
driver
circuitry
faulty.
See schematic
27404D.
Q301
Transistor
Q306
DMM set
for
4 WIRE
ohms and R SOURCE
terminals
are
not
connected.
DMM set
for
4 WIRE
ohms,
but
leads
are
reversed.
Current
fuse
F5Ol
is
blown.
ts
f
CORRECTIVE
ACTION
Check
plus
P3Ol
and matins
connecior-J201.
t4ake cergain
all
pins
are
making
contact.
"a"
bar:
Check
R3O2 pin
14
for
signal.
When "ON",
voltage
should
be approx.
+l.8~.
"b"
bar:
Check
R3O2 pin
16
"c"
bar:
Check
R3O2 pin
,l5
"d"
bar:
Check
R3O2 pin
9
'e"
bar:
Check
R302 pin
I2
"f"
bar:
Check
R302 pin
10
"g"
bar:
Check
R302 pin
13
decimal
point:
Check
R302
pin
II
Check
plug
P3Ol
and mating
connector
JZOI.
If
units
digit
missing,
check
collector
of
Q305 for
signal.
When "ON"
voltage
should
be
approx.
418~.
If
tens
digit
missing,
check
collector
of
4304.
If
hundreds
digit
missing,
check
collector
Q303.
If
thousands
digit,
minus
sign
and
function
indicator
missing,
check
collector
Q302.
On 10,000
digit,
check
collec-
tor
Q301.
If
no signals
are
present
problem
could
be tran-
sistor
or
integrated
circuit
u301.
Set
to
2 WIRE.
Connect
HI
input
to
the
same
side
of
unknown
as the
+ R
SOURCE lead.
Replace
fuse
on rear
panel.
6-21
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