Dark Testing Potential Problem PMTs Underground

PMT in dark box for dark testing underground.  LED is pulsed with NIM random pulse generator, 60 ns, 2 V pulses at 100 Hz.  Data acquisition uses LeCroy 104xi waverunner.  We tested four PMTs which had abnormal conductivity test results, plus one which was designated spare due to abnormal cold test results at BU.  The four with abnormal conductivity all tested well, and will be inserted into detector.  The designated spare continued to have abnormal positive afterpulses, likely a reflection cause by problem on base.  Will continue to be spare, and if needed base will be replaced.