Agilent Technologies 8564EC Service Manual page 418

Synthesizer Section
Unlocked Offset Lock Loop (Sampling Oscillator)
22.Short C441 with a wire jumper. (Connect the jumper from the end of
R462 nearest C441 to the end of R460 nearest C443.) This changes
the loop integrator into a voltage follower. Refer to function block AB
of A15 RF schematic (sheet 3 of 4).
23.Check the voltages at the following points:
A15U408 pin 6
A15X201 pin 1
24.If the voltages are not correct suspect A15U408.
25.Remove the jumpers.
550
+2.5 Vdc (approximately)
+2.5 Vdc (approximately)
Chapter 11