10. Check Third Converter as follows:
a. On the HP 85623, press
(PRESET)
and set the controls as follows:
Center frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
..300MHz
Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz
b. Inject a -28
dBm,
310.7 MHz signal into A15J801.
c. If a flat line is displayed within 2 dB of the reference level, but the External Mixer
Amplitude Adjustment fails, troubleshoot the Al5 RF Assembly.

A7 LO Distribution Amplifier

Note
YTO unlock errors may occur if the power delivered to the
A15UlOO
sampler
is less than -9.5
dBm.
Frequency response will be degraded in both internal
and external mixing modes if the output power is low or unlevelled.
Caution
Connecting or disconnecting the A7 bias with the HP 85623 LINE switch on
will destroy the A7 assembly. Always press
LuNE)
to turn the HP 85623 off
before removing or reinstalling W12 to either the A7 or A14JlO.
Note
Err 334 may be displayed if the LO OUTPUT connector on the front panel is
not properly terminated into a 50R termination.
‘0 0 00 00l l3
2.
0
0
l
0 0
d4
srr632e
Figure 12-2. A14J10, Solder Side of Al4 (Ignore Pin Numbers on Mating Connector)
1. Press [LINE) to turn the spectrum analyzer off. Disconnect W12 from A14JlO.
2. Connect a jumper between A14JlO pin 5 and A14J19 pin 6. Connect a jumper between
A14J18 pin 13 and A14J18 pin 1. See Figure 12-2.
3. Connect the positive lead of a DVM to A14J18 pin 14 and the negative lead to A14J18
pin 6.
4. Press
m
to turn the spectrum analyzer on.
5. The voltage measured on the DVM should be more negative than -9.4 Vdc.
6. Move the jumper from A14J18 pin 1 to A14J18 pin 2. The voltage measured on the DVM
should be more positive than
t12.3
Vdc.
7. If the voltages do not meet the limits listed in steps 5 and 6, troubleshoot the Al4
frequency control assembly.
8. Connect the positive DVM lead to A14JlO pin 1.
12-6 RF Section