Symmetricom 5071A, Assembly And Service Manual

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2. Service
Top-Level Diagnostic Tree (Diagnostic Section 1)
45
Power-on Fatal-Error Diagnostic Tree
(Subsection 1)
This subsection describes the power-on fatal-error diagnostic tree. It
assumes that the in5, +12, and -12 dc-supply voltages are all present
and within specifications.
1.1.1 Fatal-Error Interpretation
1 Observe the log contents for any of the following error messages.
QUESTION: What is the error?
If Error = Sequencer interrupt error <number>, Go to, 1.1.2
If Error = Config load err <number>, page <number>, Go to, 1.1.3
If Error = Config write error <number>, Go to, 1.1.3
If Error = Bad CBT EEPROM format, Go to, 1.1.3
If Error = CBT load error <number> page <number>, Go to, 1.1.3
If Error = none of the above, Go to, 1.3.1
1.1.2 Sequencer Error Test
This error occurs when 1MHz is absent on A3.
1 Place the short extender board (part number 05071-60051) into the
available spare slot on the motherboard (XOPTP1 and XOPTP2).
2 Use an oscilloscope to verify that a 1 MHz signal is present at the test
point labeled “+1 MHz” with an amplitude of 4 volts, 50% duty cycle, and
a nominal 20 ns rise time.
QUESTION: Is the 1 MHz signal present as specified?
If Yes: Remove power, replace A3, and retest.
If No:
Go to 1.1.2.1.
1.1.2.1 1-PPS Assembly 80 MHz Input Test
1 Remove ac power and disconnect the cable from A8J3.
2 Connect free end of the cable to the 50
Ω
impedance input of an
oscilloscope. (If a 50
Ω
input is absent, use the high impedance input with
a 50
Ω
feed-through terminator at the scope end of the cable.)
3 Apply ac power and verify that the signal at A8P3 is an 80 MHz sine wave
with at least 0.6 Vp-p amplitude.
QUESTION: Is the 80 MHz signal as described in step 3?
If Yes: Remove power, replace A8, and retest.
If No: Go to, 3.4.1.0 (A9 diagnostic tree)