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    User name R. Michaels

    Log entry time 11:33:39 on August31,2009

    Entry number 287204

    This entry is a followup to: 286945

    keyword=re: ADC18 in R-HRS

    Here is a follow-up on the saturation in R-HRS 18-bit ADC in
    ROC26 4th slot.
    Run 11735 -- fig 1.
    It looks to me like something funny about the signal that
    drives the peak to zero.  The change near event 5000 was explained
    in Kents halog 286945.
    Run 11734 -- fig 2
    Here the beam current is zero.  The data looks ok.
    Regarding the CSR from this board:  The 4th bit is always zero.  
    This could mean it has an older firmware which had zero there.  
    Later firmware versions made this bit mean "all necessary power 
    is available" and zero means a board hardware failure.  
    So it's either an old firmware version or a hardware problem.  
    Either way, we may should swap out this particular 18-bit ADC,
    although I don't actually see a problem.
    Of course if we replace it with a 16-bit, then it's just a matter
    of flagging the above unit for firmware update or diagnosis.
    None of the other 18-bit ADCs that I've checked (including 
    in Test Cage) exhibit this symptom.

    FIGURE 1

    FIGURE 2