HP 8340A Service Manual page 47

MULTIPLE LOOPS UNLOCKED
If more than one loop is unlocked at one time it is important to understand how the loops
relate to each other. The REF loop generates reference signals that are required by all other
loops. The YO loop uses signals generated by the M/N loop and the 20/30 loop.
The UNLK LED is located on the A2 Display Driver board (Block E). These LED's are
driven by the A3 Display Processor, Annunciator Latch/Driver.
The LED is turned .on by the instrument processor. The processor detects the unlock
indication from the particular phase lock loop and outputs the appropriate bits on the Data
Bus and then outputs address 15:RO to latch the data bits.
7.
FAULT ANNUNCIATOR
The FAULT 'light is used to monitor the status of 5 different internal functions. These
functions are described below. If the FAULT light is on, press
ENTRY DISPLAY will show the following.
FAULT: CAL KICK ADC PEAK TRK
The name of the function that has a problem will be fl a shing.
CAL - This refers to the Calibration Constants stored in RAM on the A60 Processor
board. The Calibration Constants are checked only when an
done or at instrument power on. If the CAL light is fl a shing something has
changed in the Cal Constants. Refer to Calibration Constants in Section VIII
Introduction for more information. If any operation is performed that updates a
Cal Constant, the processor will calculate a new checksum. After the next
PRESET]
constant(s) will still be there.
KICK-
This refers to the kick pulses used to reset the YO and SYTM. AT end -of-sweep
the YO and SYTM are tuned below their normal start frequencies by a kick pulse
generated on the A54 YO Pretune DAC/Delay Compensation board or the A28
SYTM Driver board. These kick pulses last a fi n ite period of time. If a pulses stays
on longer than it should, the processor will detect it and indicate a KICK FAULT.
Refer to the Sweep Generator- YO Loop Theory of Operation and Troubleshoot­
ing for the A54 Pretune and to the RF Section for the A28 SYTM Driver.
ADC - This refers to a check performed on the ADC circuits. This check is done at
[INSTR PRESET]
(A27 Level Control board) Theory of Operation and Troubleshooting.
PEAK -
This refers to an HP 8340A function that peaks the RF output power at one
frequency by fi n e tuning the SYTM (Tunes the SYTM to the YO frequency). This
fault can only come on if the
fl a shing, something is wrong with the circuitry that peaks the SYTM. Refer to the
RF Section (A28 SYTM Driver board or A27 Level Control board) Theory of
Operation and Troubleshooting.
TRK -
This refers to an HP 8340A function that peaks the RF output power while the
instrument is sweeping. This fault can only occur if
pushed. The TRK light indicates the same things as if PEAK were fl a shing.
The FAULT LED is located on the A2 Display Driver board (Block
driven by the A3 Display Processor, Annunciator Latch/Driver.
The LED is turned on by the instrument processor. The processor detects the error from the
particular circuitry and outputs the appropriate bits on the Data Bus and then outputs
address 15:RO to latch the data bits.
8-46
Model 8340A - Service
or power on, the FAULT light will be out, but the bad calibration
or power on. If the ADC light is fl a shing, refer to the RF Section
[PEAK]
Scans by HB9HCA and HB9FSX
[SHIFT] [MANUAL].
[INSTR PRESET]
button is pushed. If the PEAK light is
[SHIFT] [PEAK]
E).
The
is
[INSTR
has been
These LED's are