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AC VOLTS
CHECK POWER SUPPUES,
MISCELLANEOUS NOTES
INABILITY
TO
ZERO
MAY
BE
CAUSED BY LEAKY
U1211
I M W T S
OR LEAKY ~1215. IF
zEao
CAN BE
SETON 200 mVAMD2 YRANGEBYT
ISOFFON20 VRANGEC1021(
8 6
1
MAY BE WRONG VALUE.
0
AN ABNORMALLY LOW DISPLAY
IEEDICATTON AT 20 kHz
OM
200 mV
AND 2 V RANGE CAN
BE CAUSED BY
U12f
l BEING DEFECTIVE.
AMPLITUDE NONLINEARITY CAN
BE C A ~ S E D B Y LEAKY
FEEDBACK
DIODES CR1221 AND CR1222.
WlTH AC
VOLTAGE AT INPUT,
CHECK FORADCVOLTAGEATAC
CONVERTER
OUTPUT.
ACROSS
~ 1 2 2 1 ,
WHICH
C O R R E S ~ U D S ~ T O
THE INPUT VOLTAGE. FULL SCALE
INPUT SHOULD PRODUCE 2 V DC
ACROSS
C1221
ON
ANY
ACV
RANGE. MEASUREMENT DEVICE
READING WILL
BE SLIGHTLY
LOWER THAN EXPECTED BECAUSE
OF ITS LOADING EFFECT.
VOLTAGE
ACROSS 61221
CORRECT
S2-C-4,s
CHECK AC VOLTAGE
AT U1321-6.
AMPLlTUWE WlTH FULL SCALE
lfitPUT SHOULD BE
200 mV
ON
200
mV
AND 20
V RANGES,
2 V ON
2
V AND 200
V RANGES
AND 500 mV
O N
500 Y RANGE-VOLTAGEWILLBE
SLIGHTLY
LESS
BECAUSE
OF
NORMAL LOSSES BEFORE U132t.
t
I
CHECK AC
CONVERTER U1211 AND
ASSOCIATED
COMPONEMTS,
IF
AT U1321-6
SOME RANGES
WORK AND OTHERS
CORRECT
DON'T,
CHECK
GA1N SETTrNG
R E S I S T O R S
A N D
S W I T C H E S
BETWEEN U1321-6 AND U1211-2.
I
CHECK
GAIN
O F U1321. AC
VOLTAGE AT U1321-3 AND U1321-6
SHOULD BE EQUAL. NOTE THAT
I
MEASUREMENT
DEVICE
M A Y
I
DECREASE
THE
YOLTAGE
AT
U1321-3
DUE TO CAPACITANCE
AND RESISTANCE
5 0 THE TWO
MEASUREMENTS
SHOULD
BE
MADE $1 MULTANEOUSLY.
NO
L11321 EQUAL
ASSOCIATED COMPONENTS
-
CHECK INPUT SWlTCHING AND
A T f ENUATOR
COMPENSATION
CAPS C1312, C1313, AND C1311.
WHEN MAKING MEASUREMENTS AT
THE ATTENUATOR
BE
AWARE
OF
THE
L O A D I N G
EFFECT
O F
CAPACITANCE AMD RESISTANCE
OF THE MEASUREMENT DEVICE.
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