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6-14. fHgital-to-Analog Converter Test
This test checks the circuits in the signal path shown in Figure 6-6. The only circuits being
^ e d a r e ^ WgftaRo-Analog Converter (DAC). the Summing Junction, and toe c m * *
path. A voltage is generated fromthe DAC that corresponds to its full-scale An -hp- 3455A
voltmeter is connected to the IMO OUTPUT TO 3585A tomeasureLtlusvoltage.T^DAC
' riii^fa&raadjiisTawith-ASftWtoite proper value; as read by the voltroeterTIf fliea^just-
ment is possible, and the DAC steps to various values with < lOOmv error, the circuits are
considered functional. The program prints the results of the test.
tattering the Test
With the High Frequency Menu displayed, press SFK K6 to initialize the test. After in
itialization. follow the instructions displayed on the computer.
What H the Test Falls?
Assmntag that the correct digital control is provided for the DAC. the most probable cause
for not being able to make this adjustment is failure of the DAC or failure of the Summing
Junction. Use the "SWITCH" subprogram to vary the voltage output of the DAC; the
measured voltage of the IMO OUTPUT TO 3585A should vary accordingly white doing this.
If no voltage change occurs, use a probe and a voltmeter to see if the DAC voltage wffl
change at the DAC operational amplifier output. If it does, the problem is in the Slimming
Junction or the signal path following the DAC output. If no voltage change occurs^ at the
o S m ? o f the DACO-eTacrpss pins 1 and 7 of U12) while varying its digital inpu^w«h
1
"SWITCH"). then the problem is in the DAC. Refer to Service Group Three for
(
schematics, component locators, and circuit descriptions.
E q u i p m e n t S e t U p
°INPUT
ft, n «
T o p of
-hp-35601A
wr
s o
I No 3SS01 S6S0S
)
c
'Figure 6-6. Oigftal-to-Analog Converter Tost
Digital-to-Analog Converter Test
6-17/6-18
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