DIMM Troubleshooting

Hardware

• The DIMM electronics power switch is available from http://192.168.52.72. (user is lbtuser )
  This PDU (power distribution unit) allows you to power cycle the DIMM electronics box (mount/camera/focuser). See the attached document for how to use the PDU interface.
  
  
  
• Sometimes the camera will not connect when initializing. If power-cycling the electronics box does not make it connect, sometimes going up on the lift and pulling the power when its enabled will clear it.

Occasional circumstances may drive the DIMM mount to one of its external hard stops, producing an error condition that requires intervention. The document BackOffStops.pdf explains how to back the DIMM mount off its hard stops.

• BackOffStops.pdf: How to back DIMM off hard stops
• OnMountInfo.gif:Instructions for locking/releasing DIMM mount axes
• Resetting the Dimm when it hits the stops: notes on the wiki from Tim Shih (Oct-2011)

Software

• machine is dimm.mountain.lbto.org the user is dimmuser
• The webcam is accessed via the jpg file it creates constantly (see the html file in /home/telescope/dimm.html ; it is used by the auto-acquisition thread of the DIMM software for coarse acquisition.
  Using just the jpg file helped us get past the Java issues taking 100% of the cpu.
  If the webcam is bumped or move, here is the procedure for updating the target for auto-acquisition.
• When the LBT is above about 70 degrees, the DIMM auto-acquisition struggles to move the mount in small moves for acquisition. This is a balance problem that should hopefully be looked at during Summer-2017.
• Some users experience difficulty with the manual offset arrow buttons if they click too quickly. This is due to the “move” command being sent as soon as the button is pressed, and the “stop” command being sent as soon as the button is released. Therefore, if you quickly click the buttons on/off, you will experience latency problems between the client and server processes, with sometimes the client not recognizing a move has finished. It’s best to hold the arrow button down a second before releasing, rather than “clicking” it.
• Due to peculiarities and constraints on the DIMM mounting location, the up-down axis displayed is horizontal in the webcam and high speed camera views, and the left-right axis is vertical. Thus “up-down” and “left-right” on the Move Mount window refer to the physical relationship of the mount to the dome slit, not to the direction on the onscreen views.
• Software log messages
• Problems, upgrades, other things to fix
• Links to software debugging and testing notes

Typical issue after a cold restart or power outage - follow those instructions (this is due to a bug in lib-telemetry)

DimmKillServices stop
rm /lbt/data/telemetry/tcs/dimm/current.dimm.*.h5
DimmKillServices restart

Host Computer

The DIMM computer runs CentOS release 4.9.

If the disk has a problem, there is a mirrored drive that can be swapped to. If it has a file system problem, the problem will be propagated to the mirrored drive. In that case, we need a new disk with an image backup or we need to rebuild.

A catastrophic failure of the DIMM computer would require rebuilding the application on a new machine that has a PCI DV FOX board. The DV FOX board is the camera fiber interface board.

-- TomHerbst - 20 Apr 2009