HP 5334B Service Manual page 193

Set up the HP 8565A Spectrum Analyzer as follows:
FREQUENCY SPANPIV
..................
FREQUENCY BAND 0.01-1.8 GHz
....................
FREQUENCY SPAN 0.090 GHz
.....
FREQUENCY SPAN MODE PER DIV
...........
FREQUENCY SPANPIV 500 KHz
.......................
RESOLUTION BW 10 KHz
REFERENCE LEVEMNPUT ATTEN
REFERENCE LEVEL
.................
0 dBm
INPUT ATTEN
..............................
0
AMPLITUDE SCALE
..................
10 dB
.................................
SWEEP TRIGGER FREE RUN
....................................
SWEEP SOURCE INT
e. Check for the following signal peaks at 90 MHz:
U303 pin 1
-
65 dBm
U304 pin 1
-
70 dBm
U305 pin 1
-
75 dBm
f. Now, set the Spectrum Analyzers FREQUENCY SPAN to 0.990 GHz.
g. Set the HP 8656B Signal Generator to output a 990 MHz signal to INPUT C.
h. Check for the following signal peaks at 990 MHz:
U303 pin 1
-
65 dBm
U304 pin 1
-
75 dBm
U305 pin
1
-
85 dBm
i. If all the dc checks and signal tracing are good, then the 30 dB Amplifier circuit is good.
8-447. Troubleshooting the Divider Circuit
8-448. Divider U302 divides the input signal by 64. The Divider is more sensitive than the Peak Detector. Thus,
once you supply enough input signal to turn on the Peak Detector, the Divider circuit should operate.
a. Connect the 90MHz,
-
30 dBm signal to INPUT C.
b. Check the dc bias of U302 pin 1 and U302 pin 8. There should be -2.6V at both pins.
c. Verify that there is a 1.4 MHz, 1.5 Vp-p square wave with
-
2.6V dc offset at U302 pin 4.
d. Verlfy the pins 2,3, and 6 are grounded. Note that if for some reason pins 3 or 6 lost their connection
to ground, they will float down to
-
5.OV
+
0.4V and cause the prescaler to divide by 128 or 256, in-
stead of by 64.
e. If all of the above dc levels were correct, then the problem may be with bias resistor R304, or U301.
U301 might not be sending its signal to MRC U20. Verify that R304 is biasing U301 pin 5 to
-
1.2V
+0.4V and that the output, U301 pin 3, is not shorted or pull-down by resistor R302.
f. Check for a 400 mV p-p square wave with
+
2.6 V dc offset at U301 pin 3. This is the output of the
Channel C Input Amplifier and it is sent to MRC U20, which is located in the Measurement Block.
Thus, if Channel C Input Amplifier is working, perform the troubleshooting procedures in paragraph
8-358, Measurement Block Troubleshooting.
HP 5334B
-
Service Manual
8-73