2. Service
Assembly/Module Diagnostic Trees (Diagnostic Section 3)
92
A5 Diagnostic Tree
(A/M Subsection 2)
This subsection describes the A5 87 MHz PLL module diagnostic tree.
NOTE
Ensure that the instrument is in Fatal Error mode. This enables A4 to
provide a 131.77 kHz output.
3.2.1.0 Power-Supply Tests
1 Check the +5V, +12V and both -12V terminals on A5 with a DMM.
2 Verify +12V is between +12 and +12.5V to chassis.
3 Verify +5V is between 5.25 and 5.5V to chassis and -12V is
between -12 and -12.5V to chassis.
QUESTION: Are power supply voltages correct?
If Yes: Go to, 3.2.2.0.
If No: Go to, 2.1.1.1.0 (Power-supply tree).
3.2.2.0 80-MHz Signal Test
1 Disconnect coax cable from A5J1.
2 Connect free end of cable to 50 input of an oscilloscope. (If a 50 input is
absent, use the high-impedance input with a 50 coaxial-feedthrough
terminator at the scope end of the coax).
3 Verify presence of an 80-MHz undistorted sine wave with at least
0.6 Vp-p amplitude.
4 Reconnect cable to A5J1.
QUESTION: Is an ~80-MHz undistorted sine wave with at least
0.6 Vp-p amplitude displayed on the oscilloscope?
If Yes: Go to, 3.2.3.0.
If No: Go to, 3.2.2.1.
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