2. Service
Functional-Group-Diagnostic Trees (Diagnostic Section 2)
76
2.2.5.0 Analog-Signal Chain Transimpedance Test
1 Connect the 100-nA current source input lead to A6, J4, pin 9 (closest to J5
and J6). (This applies a -100 nA input signal to A14.)
2 Measure the voltage at A6J7.
QUESTION: Is the voltage difference between +6.9 and +7.5?
If Yes: Go to, 2.2.6.0.
If No: Go to, 2.2.5.1.
2.2.5.1 A6U10 10.2 and 10.3 Voltage Test
1 Use the DMM to measure the voltage difference between
A6-U10.2 and A6-U10.3 with the dip clip.
QUESTION: Is the voltage between +4.75 and +5.25?
If Yes: Remove power, replace A6*, and retest.
If No: Remove power, replace A14, and retest.
2.2.6.0 VFC Output Test 2
1 Use the high-impedance probe, frequency counter, and oscilloscope to check
frequency and amplitude of the logic signal at A6 U33-3.
2 Verify that the waveform is TTL-level pulse with a frequency between 219
and 231 kHz.
QUESTION: Does the waveform consist of TTL-level pulses between
219 and 231 kHz?
If Yes: A14 and the input section of A6 are operating correctly.
Carefully re-connect the CBT output cable to the input of
A14-J1 and resume testing.
If No: Remove power, replace A6*, and retest.
*See note at 2.2.1.1.
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