User's Manual

123
Service Manual
7-12
2. Press to open the SCOPE INPUTS menu.
Press
to open the SCOPE OPTIONS ... menu, and select:
SCOPE MODE: ■ ROLL MODE | WAVEFORM MODE: ■ NORMAL.
3. Apply a 1 kHz square wave to Input A and Input B, and change the test tool
sensitivity (V/div) to make the complete square wave visible.
4. Check TP154 (ADC-A) and TP254 (ADC-B) for the signal shown below:
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Input positive.
Input negative
150 mV/div
Input zero. 0.3 to 1.4V
A trace amplitude of 1 division results in an 150 mV voltage on TP154/255
Moving the trace position, with a zero input signal, results in a TP154/254 voltage of
about +0.3V (bottom) to +1.4V (top).
If the voltages are not correct, do steps 6 to 16; if these steps are correct, then replace
the C-ASIC.
If the voltages are correct, the error is most probably caused by the ADC, or ADC
control: continue at step 16.
5. Check TP156 (TRIGA) and TP256 (TRIGB). The TRIGA and TRIGB signals must
be the inverted input signals, with an amplitude of 50 mV per division trace
amplitude.
Moving the trace position, with a zero input signal, results in a TP156/256 voltage of
about +0.4V (bottom) to -0.4V (top).
If the voltages are not correct, do steps 6 to 16; if these steps are correct, then replace
the C-ASIC.
6. Check the supply voltages +3V3A (+3.3V), -3V3A (-3.3V), and +5VA (+5V).
If not correct trace to the Fly Back converter on the Power part.
7. Check TP151 (POS-A) and TP251 (POS-B) for about +1.1V (trace at mid-screen),
+0.4V (trace at top of screen), +1.8V (trace at bottom of screen).
If not correct check the PWM circuit (in the Digital Circuit).
8. Check TP152 (OFFSET-A) and TP252 (OFFSET-B) for about +1.1V.
9. Check TP303 (REFN) for -1.2V.
10. Check TP153 (DACTESTA) and TP253 (DACTESTB) for 0V. If TP153 is +1.7V,
the C-ASIC is in the reset state (200 mV/div fixed sensitivity); check SDAT and
SCLK, see step 15.
11. Check TP155 (MIDADCA) and TP255 (MIDADCB) for about +0.9V.
12. Press
to open the SCOPE INPUTS menu.
Press
to open the SCOPE OPTIONS ... menu, and select:
SCOPE MODE: ■ NORMAL | WAVEFORM MODE: ■ NORMAL.
Select a time base of 20 ms/div.