User name gilman
Log entry time 12:21:13 on October 9,1998
Entry number 2530
keyword=FPP low voltage problems and oscillations speculations
Notice when Sebastian starts cosmic run that FPP threshold voltages are 0.
Since this may lead to oscillations broadcasting RF affecting VDCs, decide to take
opportunistic access and look at things.
1) Two thresholds turn on but two others do not. Conclude supplies are fine, but EPICS is not speaking to them / turning them on. Maybe someone has changed things recently?
2) Notice that there seems to be no AC power in FPP level shifter. Supply does
turn on when plug it in elsewhere. There is some alarm inside crate for unknown
purpose that maybe also is not working. Think I identify circuit breakers, but they all look fine, so decide on being unable to reach people that just in case I should not
reset them. So if level shifter off leads to TDC oscillating, it will continue.
Kathy McCormick tells me Jack was looking into controlling VDC thresholds, had problems,and might have tried using two FPP DACs for them.