51
Transient Generator Troubleshooting (Figure 3-7)
The transient generator (U310-U316) allows the input power stages to switch between two load levels. It produces the
HIGH
control which is sent to the DAC circuits to switch the transient DAC output.
Troubleshooting the transient circuit consists of performing the general troubleshooting procedures if the transient circuit
will not perform any functions, or performing the frequency or toggle/pulse mode troubleshooting if there is a problem in
those areas.
General Troubleshooting
First, check the data bus and internal clock. Use signature analysis to check the SD 0-7 data lines at U310 and U311 (see
Table 3-10). Check for the presence of the 1MHz clock signal at U313-1, U312-1, U316-13, and U315-4, 12 (see Figure 3-
7).
Next, perform the front panel actions indicated in the Checkout table using a scope and logic probe to monitor the results.
Make sure that the unit is at the factory default setting of 1000Hz , 50% duty cycle.
Transient Generator Frequency
If the transient generator will not change frequency, press [TRAN ON] on the front panel and program the transient
frequencies according to the FSEL table. Check FSEL inputs at U316-1,2,3 with a logic probe. Check the 1
µs pulse
intervals at U312-14, and U316-14 with a scope.
FSEL TABLE
Front Panel FSEL INPUTS
interval between 1µ
µµ
µs pulses
Frequency 0 1 2 @U312-14 @U316-14
10000Hz LO LO LO LO
50
µs
1000Hz HI LO LO
10
µs 500µs
100Hz LO HI LO
100
µs
5ms
10Hz HI HI LO 1ms 50ms
1Hz LO LO HI 10ms 500ms
Toggle or Pulse Modes
To check the transient generator in toggle and pulse modes, run the following program:
10 LOOP
20 OUTPUT 705;"TRAN ON;:TRAN:MODE TOGG''
30 DISP "TRAN:MODE TOGG"
40 PAUSE
50 OUTPUT 705;"TRAN:MODE PULS''
60 DISP "TRAN:MODE PULS"
70 PAUSE
80 END LOOP
90 END
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