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2. Service

Functional-Group-Diagnostic Trees (Diagnostic Section 2)

2.2.2.0 A6J7 Voltage Test

1 Use the DMM or oscilloscope to measure the voltage at A6J7 and record the

result.

QUESTION: Is the voltage between 0.00 and 0.05 volts?

If Yes: Go to, 2.2.3.0.

If No: Go to, 2.2.2.1.

2.2.2.1 A6U10 10.2 and 10.3 Voltage-Difference Test

1 Use the DMM or scope to measure the voltage difference between

A6-U10.2 and A6-U10.3 with the test clip.

QUESTION: Is the voltage difference between -0.03 and 0.03 volts.

If Yes: Remove power, replace A6*, and retest.

If No: Remove power, replace A14, and retest.

2.2.3.0 VFC Output Test 1

1 Use the oscilloscope and the universal counter to measure the amplitude and

frequency of the logic signal at A6J2, pin 44 (This

is the twelfth pin from the right on the row of pins furthest away from the PCA

board surface.).

NOTE

Use the 10:1 high-impedance probe at the measurements, with the input

impedance of the oscilloscope and counter set to 1 M. Use dc coupling

and set the trigger levels to 0.15 volts at the probe output.

The waveform should consist of TTL-level pulses with a frequency between

zero and (100+ 3.210

 V)Hz, where V is the voltage measured at 2.2.2.0

above.

QUESTION: Is the TTL waveform and level within tolerance?

If Yes: Go to, 2.2.4.0.

If No: Remove power, replace A6*, and retest.

2.2.4.0 Reference Voltage Test 1

1 Measure the voltage from A6, J4, pin 9 to ground with a DMM.

(Refer to 3.9.1.1.4 for pin assignment.)

QUESTION: Is the voltage between -4.995 and -5.005?

If Yes: Go to, 2.2.5.0.

If No: Remove power, replace A6*, and retest.

*See note at 2.2.1.1.

Symmetricom 5071A Assembly And Service Manual

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