Re: current readback

[Brendan Kiburg <kiburg@npl.uiuc.edu>]

Hi Peter,
  I'm not sure how to proceed with getting the mscb working again, but you
can always turn the knob on the bertan manually up to whatever voltage the
chamber is really at and switch the toggle on the back from remote to
local.  Then you should be able to ramp the chamber down manually.  With
all chambers down you can try restarting the mscb program (as root).

  I'm pretty sure steve said that you should be able to stop and start the
mscb program without tripping the chambers, but the two times that I tried
to do this, we received hard trips.  If the chambers will be off for a
while (at least as long as it takes for the tpc to come back up), I dont
think there should be a problem ramping them down as a precaution before
restarting the mscb program.

  By the way, I was looking at the tpc current readback and noticed that a
few attempts to increase the voltage drew a lot of current.  Are there
serious problems or do we just not know yet?

I will be around for a little bit and then have a lunch
appointment.  Please let me know if I can assist you further.

Best regards,

Brendan

On Mon, 12 Dec 2005, Peter Winter wrote:

> Hi Brendan,
> 
> in the meantime we found the detailed description in order to restart 
> the frontends etc. I found it in my logbook and we performed all steps. 
> Therefore, the readback problem is solved. At the moment it seems that 
> we have a problem with the MSCB bus. We changed the voltage on muPC1 to 
> 2450V but the current readback doesn't change. Also we reset the BERTAN 
> for the TPC but we still receive the message that the HV tripped. 
> Therefore, we concluded that somehow the MSCB communication is broken. 
> At the moment, I discuss with Malte how to proceed:
> 
> - can we switch off and on the MSCB crate without tripping the chambers?
> - maybe we can first switch the BERTANs to local but then we have to set 
> them to the proper voltages since the ePCs and the muPC are still on voltage
> 
> We also tried to contact Steven (that's why I include him now to this 
> email) and hope he'll might have some input to us because he might know 
> best about it. It's tricky because we cannot ramp down the chambers now.
> Peter
>