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User name stevensm
Log entry time 17:46:50 on October14,2004
Entry number 134198
keyword=left dipole offset
We attempted to repair the left dipole offset of ~80 amps at 1000 amps of power supply output. We found that the 18 bit DAC internal to the power supply was correctly outputting 5VDC at 1000A set to value. When the offset is not present, the ZFCT correctly outputs -5VDC to the regulator, and the two signals are summed to 0. When the offset is present, the ZFCT outputs ~-4.6VDC, a value approximately comparable to the offset. That led me to believe that something on the regulator board was dropping the DAC 5VDC down to 4.6VDC, and indeed we did find an op amp which is the buffer for the DAC input which tested bad with our component tester. But changing that op amp, and the relay associated with that signal did not correct the offset.