2. Service
Top-Level Diagnostic Tree (Diagnostic Section 1)
46
1.1.3 Tube PROM Test
1 Remove power from the instrument.
2 Disconnect A2P3 from A2J2.
3 Apply power to the instrument.
4 Verify presence of +5 V ( 0.5) at pin 1 on A2J2 to chassis
ground.
5 Use a digital storage scope or logic analyzer (trigger set to 2.5V,
DC coupled, timebase to 50 us/div., no auto trigger) to verify the
signals are toggling at A2J2 pins 2 and 3 following activation of
the reset button on top of A3. The pulse levels should be
approximately 4.0 Vp-p. (Refer to the A2 connector pinout
diagrams at the beginning of the A2 diagnostic trees opposite
procedure 3.1.1.1.0.)
QUESTION: Is there +5 V at pin 1 and a toggling signal present on
pins 2 and 3 of A2J2?
If Yes: CBT ROM may be defective: contact Symmetricom for assistance.
If No: Remove power, replace A2, and retest.
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