OSCILLATOR DRIVER ALARM

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    Asad Javed
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    OSCILLATOR DRIVER ALARM:

    The OSCILLATOR DRIVERalarm indicates that at least one
    of the RF buffers is not operating properly. The alarm
    could result from a failure in the RF buffer, in the
    detection circuit on the RF buffer PWB (1A38,
    1A39), a failure on the frequency synthesizer PWB
    (1A2A2) 1A2A5) or in the alarm circuitry on the
    system controller PWB.Trouble shoot an
    OSCILLATOR DRIVER alarm as follows:
    (a)Measure DC voltage at L1 of the RF drive
    buffer PWB. If it is less than 48 volts, suspect
    the dual regulated +48Vdc power supply (see
    figure SD-24).
    (b)Use an oscilloscope to look at the signal at E1 of
    the RF buffer PWB.The signal should
    approximate a square wave of approximately
    30Vp-p. If signal is present, go to step (e).

    (c)If no signal is present, check R1 of the RF
    buffer PWB for a 15Vp-p square wave at the
    carrier frequency. If present and there is +48
    VDC at L1, +24 VDC at CR5 (cathode) and a
    nominal +0.2 VDC at Q6 (collector), suspect the
    RF buffer PWB (see figure SD-18).
    (d)If no signal is present at R1, check R59 of the
    frequency synthesizer PWB (1A2A2, 1A2A5)
    for a 15Vp-p square wave. If no signal is
    present, suspect the frequency synthesizer PWB
    (see frequency synthesizer manual).
    (e)Measure dc voltage at Q8 (collector) on the RF
    buffer PWB. If approximately 0V, suspect the
    alarm circuitry on the system controller PWB.
    If approximately 5V, suspect the detection
    circuitry (U1, Q8 and associated components)
    on the RF buffer PWB (see figure SD-18).

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