TROUBLESHOOTING AND REPAIR
SOFTWARE DIAGNOSTIC FUNCTIONS 6-36.
The instrument software includes built-in diagnostic functions to aid troubleshooting
and alignment.
Digital Control Latch Test 6-37.
Special Function 903, the Latch Test, generates continuous activity on the data and
address busses so the activity can be monitored with an oscilloscope.
When the test is initiated, the message "LAtch AA" is displayed, and the bit pattern
10101010 (Hexadecimal AA) is written continuously to each of the decoded module
I/O latch positions. The data is written to each address in sequence so that the activity
on the address bus is regular. Pressing the STEP key changes the displayed
message to "LAtch 55", and the bit pattern is changed to 01010101 (Hexadecimal 55).
Pressing the STEP key changes the pattern back to 10101010. Press any other
key to exit.
Instrument Diagnostic State 6-38.
Special Function 909 programs the instrument to a predefined state used by several of
the troubleshooting and alignment procedures. First, the instrument preset state
(special function 01) is programmed to disable most special functions. Then, the
diagnostic state is programmed immediately. The significant parameter settings of the
diagnostic state are listed in Table 6-15.
Table 6-15. Parameter Settings of Diagnostic States
Set Internal DACs 6-39.
All internal DACs can be simultaneously forced to a predetermined setting for
troubleshooting and alignment by special function. The settings are described below:
CODE
941
942
943
FUNCTION
Set all DACs to zero
Set all DACs to mid scale
Set all DACs to full scale
NOTE
The synthesizer DA C (U7) on the A6 Modulation Oscillator PCA cannot
be set to mid scale with Special Function 942.
6-14
PARAMETER
Frequency
Amplitude
AM Depth
FM Deviation
Mod Frequency
All Modulation
SETTINGS
300 MHz
-10.0
dBm
30.0%
5.00
kHz
1.00
kHz
Off
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