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    User name R. Michaels

    Log entry time 04:41:04 on November 30, 2008

    Entry number 251429

    This entry is a followup to: 251412

    keyword=DT problem back to 8% (mystery solved !!)

    DT came back to 8% during run 4054.
    This happened as a result of Yi Zhang turning off Cherenkov HV.
    We very briefly turned it back on to verify DT -> 25%. It is the cause.
    We leave the Cherenkov off now.

    Now we think what happened was: when we restarted the HV (halog 251392)
    at 02:44 we must have accidentally turned on Cherenkov leading
    to large DT. (The scaler=-1 problem was also a real problem, though.)

    Yi explains that when resetting HV one must click on the "Ch_En"
    check box on the particular slot (e.g. S14) that tripped. Click
    once to make the HV go down. Wait. Click again to bring it back up.
    Apparently it is a bad idea to "disable all" then "enable all".