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 A15TP602.
3.On the HP 8560A press SINGLE. With each press of SINGLE, the analyzer alternates between the following two states:
State 1: |
|
| |
A15J901 pin 13 (LSID) | TTL low | ||
SIG | ID | Oscillator | ON |
Signal at A15TP602 | 298 MHz f50 kHz (at least +l dBm) | ||
State 2: |
|
| |
A15J901 pin 13 (LSID) | TTL high | ||
SIG | ID | Oscillator | OFF |
3rd | LO | Driver Amplifier | Provides LO for Double Balanced Mixer |
4.With the SIG ID Oscillator on, measure the frequency at A15TP602 with a frequency counter and an active probe. If the frequency is not 298 MHz f50 kHz, refer to the SIG ID Oscillator Adjustment procedure.
5.On the HP 8560A press SINGLE until A15J901 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
6.The voltage at the R622/R623 node should measure approximately
7.If oscillator bias voltages are correct, place a 100 R resistor across SAWR U602 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 EXTernal frequency reference, line receiver U304B is disabled and U304A is on. In INTernal frequency reference, U304A is disabled and U304B is turned on.
1.Set the HP 8560A’s 10 MHz reference to internal by pressing (mCTRL), REAR PANEL, and IO MHz INT.
2.Use a spectrum analyzer to confirm the presence of a 10 MHz signal at the following test points: