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    User name Jack (Techs)

    Log entry time 19:25:42 on June 11, 2010

    Entry number 325753

    keyword=Right Dipole work

    Wednesday, after the initial drifting of the current output, we could not get the power supply to turn on due to a persistent fault. After it became clear continuing to work in the hall was not the most efficient process, we removed the firing circuit module to bench test it in the trailer. We replaced as many of the chips as we were able. It was found two of the chips on the board were getting very hot during bench testing. It seems the layout of the board left at least five of the inverting gates, over two ICs, with floating inputs (very bad for CMOS gates). Eventually, tying the inputs to ground has corrected this. While this was a problem, it is not likely the root cause of the current drift. Today, we installed the firing circuit module, which had been checked on the bench. After that we kept having the "Interlock OK" light drop out when we attempted to turn on the power supply. It was a time consuming series of checks after which we found the fault causing the problem was generated by the "Ground Fault Detection" module. Sounds like we made progress? The "Ground Fault Detection" module had been removed years ago and the fault line jumpered to ground. We found the ground line to pin 32 of the connector was disconnected. After soldering the wire back down we still had the fault. When I tugged on the wire to pin 4 the wire came free of the connector. After soldering this wire back down we STILL had the fault. We jumpered out the ground fault, to its grounded neighbor the crowbar fault (a module also removed years ago and jumpered to ground), at the Allen-Bradley module. We could now turn the supply on. However, we could not get serial communication with the supply through EPICS. In the end this seems to have been due to an incorrectly made serial cable which did not have the ground pin wired properly (my error). The cable was corrected and we once again have an operational power supply.