Symmetricom 5071A, Assembly And Service Manual

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2. Service
Functional-Group-Diagnostic Trees (Diagnostic Section 2)
67
Power-Supply Diagnostic Tree
(Functional Group Subsection 1)
This subsection describes the Power-supply diagnostic tree and provides
information for fault isolation to:
•
A1 Motherboard,
•
T1 Toroidal power transformer,
•
A11 Steering-logic assembly,
•
A12 Dc-to-Dc Converter module,
•
LF1 Line filter module/cable assembly, and
•
B1 24V Internal-Standby Battery. (Does not apply for Opt. 048).
2.1.1.1.0 AC Line-Fuse Test
QUESTION: Does the ac-line fuse blow at power-up?
If Yes: Go to 2.1.1.2.0.
If No: Go to 2.1.1.1.1.
2.1.1.1.1 A12 Power Input Test
1 Remove the instrument top/bottom covers and inner shield.
2 Apply ac power to the instrument.
3 Use a DMM to measure the input voltage (Vin) at the A12 module (across the
Vin and Vin return power input lugs on the module)
4 Verify that the voltage present is between 32 and 38 Vdc (45 and 51 Vdc for
Opt. 048) with no more than 1 Vrms ripple.
QUESTION: Does the measured voltage meet specifications?
If Yes: Go to, 2.1.3.0.0.
If No: a) Measure the dc voltage across capacitor C4 (large can
attached to A1 with screws)
b) Verify that the voltage present is between 32 and 38 Vdc
(45 and 51 Vdc for Opt. 048) with no more than 1 Vrms ripple.
QUESTION: Does the measured voltage meet specifications?
If Yes: Go to, 2.1.1.1.2.
If No: Go to, 2.1.1.1.4