8-112
Model 8340A - Service
If the above ratio is less than 0.5, then decrease A30L4 one value
to increase the center frequency. If the above ratio is greater
than 2.0, then increase A30L4 one value to decrease the center
frequency. Repeat as necessary. Refer to Table 8B-l for inductor
values. Note: this adjustment is done at the factory and normally
will not need to be repeated unless other components are changed.
Value
0.68uH
0.56uH
0.47uH
0.39uH
Table 8B-1.
IA
Inductor Values and Part Number
HP Part Number
Value
HP Part Number
9140-0141
0.33uH
9100-0368
9100-2256
0.27uH
9100-2252
9100-2255
0.22uH
9100-2251
9100-2254
With -8.0 Vdc applied to TUNE, adjust A30C4 until the oscillation
frequency is 100 MHz +100 Hz. Remove the de source from TUNE and
reconnect the cable at A30Jl to close the Reference Loop. If TUNE
changes less than +1.0 V (from -8.0 V}, then readjust A30C4 until
TUNE (closed loop)--8.0 V; if TUNE changes more than +1.0 V, then
trouble-shoot the A29 Reference Phase Detector.
100 MHz Buffer Amplifiers B
The signal level of the 100 MHz OUT signals at A30Jl, J2, and J3
should be
O
dBm +l dB. If no signal is present at J3, then
troubleshoot Q9,-Q8, and the 100 MHz Oscillator. If the output of
J3 is correct but the signal at J2 and/or Jl is low or missing,
then troubleshoot the signal path that includes Qll and Q6.
The approximate bias voltage levels for the transistors in the 100
MHz Buffer Amplifiers is shown in Table 8B-2.
Table 8B-2. Approximate Bias Voltage Levels for
JOO MHz
Buffer Amplifier
Transistor
Q6
Q7
08
Q9
Qll
Emitter
3.8
3.8
4.3
5.0
3.8
Base
4.5
4.5
5.0
5.5
4.5
Collector
9.2
9.1
10.0
11.0
9.3
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