Table 10-9 Voltages In Fm Coil And Main Loop Drivers - HP 8560E Service Manual

indicated in the FREQ DIAGNOSE menu will be negative when
locking to lower sidebands. Refer to function blocks E, M, and N of
A14 frequency control schematic in the
Set the HP 8560E/EC to the following settings:
Center frequency .................................................. 300 MHz
Span .............................................................................. 0 Hz
37.Remove jumper A14J23 and connect a dc power supply to A14J23
pin 2. Connect ground to A14J23 pin 3. Set the dc power supply to
+7.5 Vdc.
38.Verify the nominal test-point voltages listed in
page 545.
39.Change the input voltage to −7.5 volts and re-verify that the voltages
listed in Table 10-9 on page 545
polarity.
40.Change the
CENTER FREQ
Hz. This will change the switch setting of U326A and invert the
voltages listed in
Table 10-9 Voltages in FM Coil and Main Loop Drivers
Measurement Points
A14U405 pin 6
A14U322 pin 2
A14J17 pin 4
Check main coil coarse and fine DACs (steps 41-44)
41.The main coil coarse and fine DACs correct any initial pretune
errors in the YTO main coil. The DACs adjust the FM-coil current to
zero before any sweep begins. Refer to function block J of A14
frequency control schematic.
42.Set the HP 8560E/EC to the settings listed below. This sets both
DACs to 128 (the DAC setting range is 0 to 255).
Center frequency .................................................. 300 MHz
Span .............................................................................. 0 Hz
Trigger ......................................................... SINGLE, EXT
(with no external trigger connected)
43.Press ,
SAVE PWR ON STATE
44.Place jumper A14J23 in the TEST position and turn on the spectrum
analyzer.
Check main coil tune DAC (steps 45-49)
Chapter 10
are the same except for a change in
to 678.8 MHz with the span remaining 0
Table 10-9 on page 545.
and turn off the spectrum analyzer.
Synthesizer Section
Unlocked YTO PLL
Component Level Informatio
Table 10-9 on
Voltages
+2.8 Vdc
0 Vdc
>+10 Vdc
n.
545