Cal Oscillator Unlock at Beginning of IF Adjust

1.Turn the spectrum analyzer luNE) switch off and then on. The words IF ADJUST STATUS appear on the display 10 seconds after the instrument is turned on (assuming the rest of the instrument is working correctly). Immediately observe the lower right corner of the display for error messages. If the message ERR 499 CAL UNLK appears (before errors ERR 561, 562 and 565), the cal oscillator is unable to phase-lock. Expect to see the ERR 499 message for only about 1 second.

2.If the spectrum analyzer registers an unlocked cal oscillator, continue with step 3 to verify the presence of externally supplied signals.

3.Check A4U811 pin 9 for a 100 kHz TTL-level square wave verifying operation of A4U811, A4Q802, and the 10 MHz input signal from A4J7.

4.Check the $15 VF, i-5 VF and -15 V power supplies, and +lO V reference on the A4 assembly.

5.Check that A4U807 pin 5 (CALOSC-OFF) becomes TTL low (0 V) at the start of a FULL IF ADJ (press (CAL) and FULL IF ADJ ). The phase modulation output at A4U804 pin 8 should also remain at 0 volts. If these checks are correct, troubleshoot blocks V, W, X, and Y. See Figure 8-23, Cal Oscillator Block Diagram.

Inadequate CAL OSC AMPTD Range

Refer to function block AC of A4 Calibration Oscillator Schematic Diagram in the HP 856OA/61B/63A Spectrum Analyzer Component Level Information binder.

1.If A4R826, CAL OSC AMPTD, has inadequate range to perform the IF Amplitude Adjustment, press LCAL).

2.Rotate A4R826 fully clockwise and disconnect W52 (coax 9) from A5J4.

3.Connect A5J4 to the input of a second spectrum analyzer.

4.Set the other spectrum analyzer controls as follows:

Center Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7MHz Reference Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -30 dBm

5.Observe the spectrum analyzer display while pressing FULL IF ADJ . The signal level should be above -34.55 dBm. If the signal level is incorrect, continue with step 7.

6.Rotate A4R826 fully counterclockwise. The signal should be below -36.25 dBm. If the signal level is correct at both settings, troubleshoot the A5 IF assembly. If the signal level is incorrect, continue with step 7.

7.Troubleshoot the ALC loop on this assembly using the following steps:

a.Connect a positive DVM probe to A4J9 pin 4.

b.On the spectrum analyzer press ICAL).

C. Press FULL IF ADJ . Observe the DVM reading between the displayed messages IF ADJUST STATUS: 300 kHz RBW and IF ADJUST STATUS: 3 kHz RBW. Duringthistime

period, the voltage should be within a 2 to 10 Vdc range.

d. Observe the DVM reading while IF ADJUST STATUS: AMPLITUDE is displayed. The reading should be within the 2 to 10 Vdc range.

IF Section 8-35