HP 11793A Operating And Service Manual page 37

Microwave Converter Model 1 1793A
RF
Devices (Service Sheets
1 and 2)
Because of the diversity of test equipment and techniques available for troubleshooting the
high-frequency devices, no specific procedures are given. Check the performance parameters of the RF
devices against the following table, Table 10. Also check connectors and cables.
Table 10. Performance Parameters
Device
AT1
3 dB
Attenuator
FL1
Low-Pass
Filter
s1,
s2
Switch
u1
LO
Amplifier
Performance Parameters to Check
Attenuation: 2.5 to 3.5 dB at 18
GHz
2.0
to
4.0
dB at
26.5
GHz
SWR:
4.251
at
26.5
GHz
~~ ~~
3 dB Corner: 900 to
1100
MHz
Passband Insertion
Loss: <0.25
dB at
800
MHz
Insertion Loss:
4 . 5
dB at
26.5
GHz
SWR:
<2.0:1
at
26.5 GHz
Frequency Range:
18
to
26.5
GHz
Gain:
>11
dB
SWR:
C2.51
u2
IF
Amplifier
u3
Mixer
Frequency Range:
10
to 700 MHz
Gain: 14 dB
SWR:
<1.8:1
LO Frequency Range:
2
to
26.5
GHz
RF Frequency Range: 1.3 to
26.5 GHz
LO Power: >+8 dBm
Conversion Loss:
<lo
dB
SWR:
<4:1
Control Devices (Service Sheet 3)
Set a power supply to 0 Vdc and connect i t to the FREQ OFFSET INPUT connector. Set the supply to 0,
+3,
and
+ S
Vdc respectively, and compare the logic levels of the logic devices with those listed in Table 9.
When specifically checking the drive transistors 4 2 , Q3,Q4, or QS, note the following:
The switch solenoids automatically disconnect after completion of switching. Therefore, it is difficult to
distinguish between a drive transistor that is on but not drawing current, or one that is off and not
drawing current. The collector voltages will differ by only a few mV. If any of the transistors are known
to be working, compare the on and off voltages of the suspected transistor against those of a known good
one.
Power Supplies (Service Sheet
3)
Check the points indicated in the schematic diagram for dc level and ac ripple. Note that the +SV
Regulator is dependent on the
+
12V Regulator.
26