Fluke 8021B - Page 63

8021
B
Table
4-6. Troubleshooting
Guide
TEST
AND
SYMPTOM
POSSIBLE
CAUSE
INITIAL PROCEDURE
BT is
displayed
when unit is turned
on.
Low
battery, Q3, U2,
U1, U7,
U8. (See
also
operating
note for A81
accessory.)
Display blank.
Dead
battery,
power
switch, VR2
shorted, U1
,
battery
connector.
DISPLAY TEST
One or more
segments
will not light
through entire test,
Display
interconnect,
display,
or A/D
Converter U1.
Decade
inoperative
or one or more
segments
always lit.
U1.
Improper
decimal point
indication.
Range
switches, Z6,
U2,
or display.
(Check
signals at
U2
to
isolate.)
Minus
sign
improperly
displayed. U1.
Display lit but does
not
respond to
changes
in
input.
Reference
VRl,
crystal
Y1,
A/D
Converter U1.
RESISTANCE
TEST
Displayed
reading is
out of
tolerance
on at least
one
but not
all
ranges.
Range
resistor Z1
.
Readings
are noisy
on all ranges.
Thermistor
RT1, R2 open.
Readings
are out
of tolerance on
high
ohms.
RJ1
,
RJ2,
RJ3, RJ4
damaged from
severe
overload.
Residual
reading
with test leads
open
PCB
is
contaminated (see
cleaning
procedure, Section 4.)
CONTINUITY
TEST
Tone
doesn’t sound
when test
leads
are shorted.
S1G,
S8B,
AR20, U20,
LSI, Board
interconnection,
defective
test lead,
test
lead in
mA jack.
DC
VOLTAGE
TEST
Display
reading is out
of tolerance
on 200
mV range.
Out
of
calibration
(DC), Vref
(VRl) in
error, Z2,
U1,
SI.
4-11