[Dsg-hallb_magnets] Torus CERNOX board failure

[Ruben Fair]

Brian, 

This looks very encouraging. 

It certainly sounds like we should remove C34 from all the CERNOX boards. 

However, before we do that, a couple of questions: 

1. Do we understand why C34 failed after a period of time (about one year for one of the chassis?). I know you said that it might be a bad component batch issue. 

2. By removing C34, could we be moving the problem elsewhere with another imminent component failure down the road? 

If we cannot answer the above questions satisfactorily, I would recommend that we leave the remaining boards as they are. 

Can you check and give me a list of which CERNOX sensors are interlocked to produce either a controlled ramp down or a fast dump? 

There may be a way that we can avoid fast dumps if the boards go bad during a Physics run, as a splice which is slowly going bad will first produce a slowly increasing voltage followed by a slowly(?) increasing temperature, whereas a board failure causes the splice temperature read back to suddenly jump to a high value. 

Regards 

Ruben 



From: "Brian Eng" <beng at jlab.org> 
To: "Ruben Fair" <rfair at jlab.org>, "dsg-hallb magnets" <dsg-hallb_magnets at jlab.org> 
Cc: "bachiman" <bachiman at jlab.org>, "Probir Ghoshal" <ghoshal at jlab.org>, "Denny Insley" <dinsley at jlab.org> 
Sent: Thursday, October 12, 2017 3:17:42 PM 
Subject: Re: Torus CERNOX board failure 

Forgot to send to mailing list, here's the results of swapping the boards out: https://logbooks.jlab.org/entry/3488318 

I'm not sure what the expected accuracy/precision of the LV chassis and/or Cernox is, but it seems like a few mK difference is negligible? 

> On Oct 11, 2017, at 10:51 AM, Brian Eng <beng at jlab.org> wrote: 
> 
> Hi Denny, 
> 
> I plan on swapping the PCB out today sometime before lunch. 
> 
> So there will definitely be some alarms. I'll also need to restart the cRIO once the swap out is complete, which might cause additional alarms. 
> 
>> On Oct 10, 2017, at 10:27 AM, Ruben Fair <rfair at jlab.org> wrote: 
>> 
>> Brian, 
>> 
>> Torus Chassis #4 should be fine. 
>> 
>> Please just let Denny know before you swap it out as the splice temperature on the hex beam will trip the interlock again as it did last time. 
>> 
>> Ruben 
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