HP 8560A, Service Manual

Page: 412 / 450

1. Set the HP 8560A to the following settings:
TRIGGER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..SINGLE
SIG ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ON
2. Use an active probe with another spectrum analyzer to measure the signal level at
3.
On the HP 8560A press
SINGLE.
With each press of the analyzer alternates
between the following two states:
State 1:
pin 13 (LSID)
SIG ID Oscillator
Signal at
TTL low
ON
298 MHz
(at least
State 2:
pin 13 (LSID)
SIG ID Oscillator
3rd LO Driver Amplifier
TTL high
O F F
Provides LO for Double Balanced Mixer
4. With the SIG ID Oscillator on, measure the frequency at with a frequency
counter and an active probe. If the frequency is not 298 MHz refer to the SIG ID
Oscillator Adjustment procedure.
5. On the HP 8560A press
SINGLE
until pin 13 is at TTL low. Diodes CR603 and
CR605 should be forward biased and CR604 should be reverse biased (approximately 6 Vdc
reverse bias). Diodes CR501 and CR502 should be forward-biased, disabling the 3rd LO
Driver Amplifier.
6. The voltage at the node should measure approximately -5 Vdc, biasing
on.
7. If oscillator bias voltages are correct, place a 100 resistor across SAWR pins 1 and
2. If the SAWR has failed, this will provide the equivalent loss of a correctly functioning
SAWR, and the circuit will begin to oscillate.
10 MHz Reference
The HP 8560A 10 MHz reference consists of 10 MHz TCXO (Option 003: A21 OCXO)
with associated TTL level generator and distribution amplifier. The TCXO and TTL level
generator (or OCXO) are turned off when using an external 10 MHz reference. Also, with the
analyzer set to
frequency reference, line receiver is disabled and is
on. In frequency reference, is disabled and is turned on.
1. Set the HP 10 MHz reference to internal by pressing
REAR PANEL,
and MHz INT.
2. Use a spectrum analyzer to confirm the presence of a 10 MHz signal at the following test
points:
A15J303 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..>-l0
A15J304 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..>-l0
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11-14 RF Section