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9. The measured voltage should be approximately
Vdc. If the voltage is not
Vdc,
troubleshoot the Al4 frequency control assembly.
10. Connect the positive lead of a DVM to
pin 15. The voltage should measure within
of the Gate Bias voltage listed on the A7 label.
11. If this voltage is not within the correct range, refer to the “LO Distribution Amplifier
Adjustment” in Chapter 2, “Adjustment Procedures.”
12. If the voltage varies between 0 Vdc and -2 Vdc, adjust the Gate Bias for a DVM reading
within
of the Gate Bias voltage listed on the A7 label. If the voltage does not
vary between 0 Vdc and -2 Vdc, troubleshoot the Al4 Frequency Control Assembly.
13. Disconnect the jumper from
to
Press
to turn the spectrum
analyzer off. Reconnect W12 to
Press
to turn the spectrum analyzer on.
14. If the DVM reading changes significantly, the A7 is probably defective.
A8 Low Band Mixer
1. Connect the HP 85623 CAL OUTPUT to the INPUT
connector.
2.
Set the HP 85623 as follows:
Center frequency
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz
Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3. Check to see that A8 is receiving the -5 V and -4 V supply voltages from Al4 via W12.
4. Using another spectrum analyzer, check for approximately -21
(300 MHz) at the
input of A8. (This level can easily be measured at the output of FL1 by disconnecting W45
from
5. If the level at the input of A8 is less than -25
suspect FL1 low-pass filter, A10
RYTHM, or A9 input attenuator. Refer to power levels shown on Figure 12-8, HP 85623
RF Section Troubleshooting Block Diagram.
6. Check for approximately -30
(3.9107
at the output of A8. (This level can
easily be measured at the output of FL2 by disconnecting W57 from FL2.)
7. If the level at the output of A8 is less than -35
suspect A8 low band mixer or FL2
low-pass filter.
RF Section 12-7
Summary of Contents for 8562E
Page 21: ...A l HP 85623 Interconnect Block Diagram A 5 Contents 14 ...
Page 205: ...8560E Series sl131e FIGURE 5 3 PARTS IDENTIFICATION MAIN CHASSIS v ...
Page 219: ...FL 4 Bl Figure 6 9 Rear View BTl A20 SK162 Major Assembly and Cable Locations 6 l1 ...
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