HP 5334B - Page 191

8-441. Determining the Failed Circuit in the Channel C Block
8-442. To troubleshoot the Channel C Block, you must determine which of the following three categories the
problem falls into:
The Peak Detector does not enable the Divider, resulting in no output at pin 4 of U302 (Divider).
The Peak Detector properly enables the Divider, but the output of Divider (Pin 4 of U302) is in-
correct or
nonexistent.
The Peak Detector improperly enables the Divider. The Counter works properly with a signal ap-
plied to Channel C,
but it randomly counts when the signal is removed from the Channel C input.
8-443. The following procedure will help determine which category a failure falls into. Note that U306 pin 1 is
the output of the Peak Detector. When pin
1 is at - 1.2V 2 0.4V, the Peak Detector enables the Divider; and
when pin
1 is at - 5V 2 0.4V, the Peak Detector disables the Divider.
8-444. The flowchart in Figure 812, simplifies the Channel C troubleshootingprocedures.
I
90 MHz OR 990 Wz
SIGNAL TO INPUT C
I
MONITOR
U306 PIN
1
NOT -1.2V ? 0.4V
1
REMOVE SIGNAL
TO INPUT C
CHECK OUTPUT
OF U303 PIN 1.
(30dB AMPLIFIER
n OUTPUT
90 OR 990 MHz
I I
NO OUTPUT
IS PRESENT
(90 OR 990
MHz
NOT PRESENT)
THRESHOLD COMPARATOR AMPLIFIER IS WORKING.
THRESHOLD COMPARATOR
TROUBLESHOOTING
TROUBLESHOOTING TROUBLESHOOTING TROUBLESHOOTING.
(PARAGRAPH
8-453:
(PARAGRAPH 8-447) (PARAGRAPH 8-449) (PARAGRAPH 8-445)
*NOTE THAT WHEN THE COUNTER OPERATES PROPERLY WITH THE 90 MHz INPUT
SIGNAL, REPEAT THE STEPS IN THIS FLOWCHART WITH THE 990 MHz INPUT SIGNAL
HP 5334B - Service Manual
8-71