Fluke 8021B Instruction Manual page 63

8021
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
T one
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