Changes between Version 56 and Version 57 of PublicPages/MayallZbandLegacy/NotesforObservers/Problems

Timestamp:

Apr 16, 2016 3:08:30 PM (8 years ago)

Author:

Robert Blum

Comment:

--

PublicPages/MayallZbandLegacy/NotesforObservers/Problems

@@ -275 +275 @@
 '''Symptoms:''' 
 - Images appear elongated. In April 2016 the PA was ~20 - 30 and possibly due to a valve issue in the 4MAPS system.
-- 4MAPS o10, o11 might show blue signifying a delta psi > 1 indicating an open valve. 
+- 4MAPS o10, o11 might show blue signifying a delta psi > 1 indicating an open valve. The valve stuck at blue (delta psi > 1) during an exposure usually, but not always, leads to elongated images since forces on the mirror may be bad.
 
 '''Frequency:''' Rare. Occurred on several nights in April, 2016.
 
 ''' Fix '''
- You can tell if the valve is stuck open if the “light” on the 4MAPS display of the airbags turns blue (for o11 or o10) for an extended period of time (more than 30 sec, say). Flickering between red/yellow/green does not count; However, if the valve is stuck open, the color on the light should go from green to yellow to red to blue. Looking at the engineering gui for 4MAPS will show the pressure reading dropping. If it is stuck on blue, then the fix Bob recommends is the following: manually command (using the 4MAPS gui) the pressure on the problematic airbag lower than the reading. This should try and force the exhaust valve to open. Then set the pressure back up to the nominal reading; this should try and force the exhaust valve to close. This can be done without moving the telescope, but you probably want to stop the mosbot script, since you don’t want the script to command the telescope to move while you are repressurizing the bag. If this test does not work with the telescope in its current position, then the next step is to take the telescope to zenith and repeat the procedure. 
+ You can tell if the valve is stuck open if the “light” on the 4MAPS display of the airbags turns blue (for, e.g., o11 or i11) for an extended period of time (more than 30 sec, say). Flickering between red/yellow/green does not count; However, if the valve is stuck open, the color on the light should go from green to yellow to red to blue. 
+
+ Looking at the engineering GUI for 4MAPS will show the pressure reading dropping. If it is stuck on blue, then the fix Bob Marshall recommends is the following: 
+ - manually command (using the 4MAPS gui) the pressure on the problematic airbag '''lower than the reading.''' This should try and force the exhaust valve to open. 
+
+ - then set the pressure back '''up to the nominal reading'''; this should try and force the exhaust valve to close. 
+
+ This can be done without moving the telescope, but you probably want to stop the mosbot script, since you don’t want the script to command the telescope to move while you are repressurizing the bag. 
+
+ If this test does not work with the telescope in its current position, then the next step is to take the telescope to zenith and repeat the procedure.