There is.
It is located inside the shim power supply for Inova and VNMRS/DD2 systems (a bit hard to get to, best by pulling out the shim power supply).
Unfortunately, I don’t know where the same switch is located on a Mercury, but I know those didn’t require to change the magnet polarity, either.
- Knut
> On Jul 7, 2015, at 9:43 PM, Ron Crouch <roncrouch1_at_mac.com> wrote:
>
> I believe there is a similar jumper for lock board on all Varian consoles.
> Ron
>
> On 7/6/2015 12:11 PM, Plant,Daniel wrote:
>> Hi Neil,
>> I’ve seen this symptom in the past when the Z0 polarity is wrong.
>>
>> On the old GE systems, there was a jumper inside the lock module.
>> On a Bruker with a BSMS, the jumper is on the adaptor plate to the shims.
>>
>> If nothing has changed on your system since it worked before, maybe a software setting got reset?
>>
>> The varian folks might have some insight on this…
>>
>> Dan
>>
>>
>> From: Jacobsen, Neil E - (neil) [mailto:neil_at_email.arizona.edu <mailto:neil_at_email.arizona.edu>]
>> Sent: Monday, July 06, 2015 12:50 PM
>> To: ammrl_at_ammrl.org <mailto:ammrl_at_ammrl.org>
>> Cc: Bao, Kevin - (kbao)
>> Subject: AMMRL: Negative lock level on Varian Mercury-400
>>
>> I sent a query a while ago about pumping the vacuum space of a donated Mercury-400. We are now at field and everything works fine EXCEPT:
>>
>> The deuterium lock will lock in perfectly with lockphase set to 0 or 360, but the lock signal is negative. The display goes down rather than up when it locks. The field is stable and you can do long acquisitions. If I set the lock phase to 180, it doesn’t lock and the lock frequency drifts away from zero frequency.
>>
>> The problem is that you can’t shim on the lock signal. The shim display (red thermometer) shows zero lock level because it can’t display the negative lock signal.
>>
>> I’ve tried many combinations of rebooting the host computer, restarting the acquisitons computer, power cycling the console, etc. I considered the possibility that I’m locked on a 2H sideband, but I get a 1H spectrum centered in the spectral window normally using the standard parameters and tof=0, and I can’t find any other 2H signal in the complete range of Z0 (-2048 to 2048).
>>
>> I have to assume that some component in the lock system has gone bad during the long (4 year) sleep of the console, but I keep wondering (since it’s a Varian) if it might be a software issue. I would appreciate any suggestions.
>>
>> Neil
>
>
Received on Thu Jul 09 2015 - 08:47:16 MST