Model 739A Page 3
SECTION I1
OPERATION
NOTE
Calibrate the device under test with an accurate --
voltage standard, such as the Model 738A
Always use the OUTPUT ATTENUATOR range
Voltmeter Calibrator. This voltage standard should
that corresponds to the desired input to the device
have an output frequency between 100 and 1000 cps.
under test. This will assure a Test Set meter
indication near SET LEVEL.
1) Connect the device under test to the Frequency
Response Test Set OUTPUT connector, using the
5) Set the meter in the Test Set to SET LEVEL
special terminated output cable provided.
with the METER SET control.
2) Connect a suitable oscillator, such as the @
Model 200s Oscillator, to the EXTERNAL INPUT
6) Shift to any other frequency within the range of
connector on the Frequency Response Test Set.
the Test Set or external oscillator. Return
the meter to SET LEVEL using the oscillator
AMPLITUDE control. Note any deviation from
3) Set the external oscillator to the frequency used
the reference set in step 4 on the device under
for calibration.
test.
4) Set the RANGE SELECTOR to EXTERNAL.
Set a reference on the device under test using the 7) Repeat steps 3 through 6 if you change the range
switch on the device under test. Repeat step 6 for
external oscillator AMPLITUDE control and the
all frequencies you desire to check.
OUTPUT ATTENUATOR of the Test Set.
SECTION Ill
MAINTENANCE
The internal oscillator is a single pentode (V2) glow discharge tubes to regulate the differential
located inside the shield on top of thechassis. The amplifier voltages.
oscillator plate and screen voltages are controlled
Tube element voltages are not listed on the sche-
by a series regulator triode (Vl). This series
matic diagram since they vary radically with fre-
regulator is controlled by a two stage differential
quency and output AMPLITUDE control setting.
amplifier (V3 and V4) that senses the amplitude of
the voltage applied to the OUTPUT AlTENUATOR.
The only adjustments in the oscillator circuit are
The combined action of the series regulator, dif-
for initial dial calibration and should not need fur-
ferential amplifier and output amplitude sensing
ther attention. Another adjustment (C16) is pro-
circuits keeps the output constant over the range
vided in the meter circuit. This meter frequency
of the internal oscillator.
response adjustment should not be touched unless
you have accurate means of checking the accuracy
' The power supply circuit is conventional, using of the reference meter between 7 and 10 mc. |