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TELESCOPE OPERATIONS


TROUBLESHOOTING GUIDE


This page is devoted to listing previously seen problems and their potential fixes. With the complexity of the GBT and its numerous systems, some problems may have several different causes. Keep that in mind when using this guide.

Jump straight to:


Antenna Control


SYMPTOM: Cannot get antenna control via M&C
PROBLEM (SOLUTIONS)

  • M&C not passed control by the OCU (Pass control by OCU or OCT).
  • Illegal commanded position in GO/Cleo (Check positon).
  • Illegal commanded center frequency imbedded in the glish setup script (Check script for erroneous value).


SYMPTOM: Telescope does not move in Az/El after pressing the Move To button
PROBLEM (SOLUTIONS)

  • Az/El drives not enabled (Check Drives Tab; enable drives).
  • M&C does not have control (Check Drives Tab; CCU should be set to Enabled with NRAO as control source).
  • GBT control may be in simulated mode (Check to see if sourced to Real mode).
  • Oper. Mode not set to Do Scan (Set to Do Scan).
  • Illegal commanded position in GO/Cleo (Check commanded positions. Pressing the Update button then reentering coordinates or reselecting coordinate system may also help.).
  • Problem with observers setup script (Illegal position, coordinate mode, observing frequency, or combination. Check script for problems).
  • Az/El movement inhibited due to E-Stop or Soft Stop button depressed (Check/clear E-stop axis faults).
  • Antenna in SafeMode or SafeHoldMode state (Check message window for systems not enabling properly; clear faults).
  • Antenna/Antenna Manager in fatal fault status (Check message window; clear faults).
  • Loss of Manager, Accessor, or Transporter (Check message window for host computer failure; restart host system if required).
  • No power to feed arm servo systems (Check circuit breakers in D1-A (Level 1, Power Substation) and/or D-15 (Level 3, Receiver Room)).


SYMPTOM: Cannot retract elevation stow pin
PROBLEM (SOLUTIONS)

  • M&C does not have control (Check Drives Tab; CCU should be set to Enabled with NRAO as control source).
  • Oper. Mode not set to UnstowAzEl (Set to UnstowAzEl).
  • Movement inhibited due to E-Stop or Soft Stop button depressed (Check/clear E-stop axis faults).
  • M&C Software failure (Verify by trying to complete move using the OCU/OCT. Report M&C problem to computing division if required).
  • Mechanical failure (Report problem to maintenance).


SYMPTOM: Cannot insert elevation stow pin
PROBLEM (SOLUTIONS)

  • M&C does not have control (Check Drives Tab; CCU should be set to Enabled with NRAO as control source).
  • Oper. Mode not set to StowAzEl (Set to StowAzEl).
  • Stow pin insertion inhibited. Stow pin not aligned with stow hole (Check elevation encoder position).
  • Movement inhibited due to E-Stop or Soft Stop button depressed (Check/clear E-stop axis faults).
  • M&C Software failure (Verify by trying to complete move using the OCU/OCT. Report M&C problem to computing division if required).
  • Mechanical failure (Report problem to maintenance).


SYMPTOM: Elevation stow pin retracts when not commanded
PROBLEM (SOLUTION)

  • Unstow command from M&C or OCU still running in background (Do allstop from OCU/OCT after pulling stow pin).


SYMPTOM: Turret not responding to commanded receiver change
PROBLEM (SOLUTIONS)

  • Turret rotation inhibited. Antenna not in Access position (Verify elevation is 77.850).
  • M&C does not have control (Check Drives Tab; SCU should be set to Enabled with NRAO as control source).
  • Oper. Mode not set to SelectFeed (Set to SelectFeed).
  • Movement inhibited due to E-Stop or Soft Stop button depressed (Check/clear E-stop axis fault).
  • Turret rotated into a limit (Check turret location in Optics Monitor window or on OCU/OCT. If in limit and cannot move, notify maintenance).
  • M&C Software failure (Verify by trying to complete move using the OCU/OCT. Report M&C problem to computing division if required).
  • Mechanical failure (Report problem to maintenance).


SYMPTOM: Turret unlocks and rotates to commanded position, but does not lock
PROBLEM (SOLUTION)

  • Computer or turret alignment switch not sensing correct turret positioning (Command to a position at one end of the turret wrap. Follow this by commanding to the other end. Retry to desired position. If not successful after repeated tries, notify maintenance).


SYMPTOM: Elevation interlock exists after rotating turret to S-band position
PROBLEM (SOLUTION)

  • Confirm turret stow pin is extended, turret locked.


SYMPTOM: Subreflector servos not responsive
PROBLEM (SOLUTION)

  • Subreflector not enabled (Check Drives Tab; enable control to Subreflector servos).

  • SCU not in M&C control (Check Drives Tab; SCU should be set to Enabled with NRAO as control source).

  • Subreflector Mode on Antenna Control window not set correctly (Set to to one of the subreflector modes).

  • SCU not enabling properly (Try passing control to the OCU/OCT then back to M&C again. If no response, reboot SCU Interface).

  • A servo axis is in a limit (Check Subr Position Ctrl Tab; command axis out of limit).

  • No power to feed arm servo systems (Check circuit breakers in D1-A (Level 1, Power Substation) and/or D-15 (Level 3, Receiver Room)).

  • M&C Software failure (Verify by trying to complete move using the OCU/OCT. Report M&C problem to computing division if required).

  • Mechanical failure (Report problem to maintenance).


SYMPTOM: Subreflector shows delta limit fault
PROBLEM (SOLUTION)

  • One or more axis exceeded delta limits (If only "limit" or "warning" messages are noted, use OCU, OCT, or M&C to slowly back out the problem axis. If final limit messages are noted, the PMU must be used at the subreflector to slowly back out the problem servos).


SYMPTOM: Prime Focus servos not responsive
PROBLEM (SOLUTION)

  • Prime Focus not enabled (Check Drives Tab; enable control to Prime Focus servos).

  • SCU not in M&C control (Check Drives Tab; SCU should be set to Enabled with NRAO as control source).

  • Subreflector Mode on Antenna Control window not set correctly (Set to Prime mode).

  • SCU not enabling properly (Try passing control to the OCU/OCT then back to M&C again. If no response, reboot SCU Interface).

  • A servo axis is in a limit (Check Prime Focus Ctrl Tab; command axis out of limit).

  • No power to feed arm systems (Check circuit breakers in D1-A (Level 2, Power Substation) and/or D-15 (Level 3, Receiver Room)).

  • M&C Software failure (Verify by trying to complete move using the OCU/OCT. Report M&C problem to computing division if required).

  • Mechanical failure (Report problem to maintenance).


SYMPTOM: Prime Focus boom not retracting/extending (OCT)
PROBLEM (SOLUTION)

  • Subreflector not fully stowed.

  • No power to feed arm systems (Check circuit breakers in D1-A (Level 1, Power Substation) and/or D-15 (Level 3, Receiver Room)).

  • Mechanical failure (Report problem to maintenance).


SYMPTOM: Prime Focus boom not retracting/extending (OCT)
PROBLEM (SOLUTION)

  • Subreflector not fully stowed (Stow it).

  • No power to feed arm systems (Check circuit breakers in D1-A (Level 1, Power Substation) and/or D-15 (Level 3, Receiver Room)).

  • Mechanical failure (Report problem to maintenance).


SYMPTOM: Prime Focus boom not retracting/extending (M&C)
PROBLEM (SOLUTION)

  • M&C does not have control (Check Drives Tab; CCU and SCU should be set to Enabled with NRAO as control source).

  • Oper. Mode not set to ChangeOptics (Set to ChangeOptics).

  • Subreflector not fully stowed (Stow it).

  • No power to feed arm systems (Check circuit breakers in D1-A (Level 1, Power Substation) and/or D-15 (Level 3, Receiver Room)).

  • M&C Software failure (Verify by trying to complete move using the OCU/OCT.).

  • Mechanical failure (Report problem to maintenance).


Receivers and IF


SYMPTOM: LO Power at the receiver is too high/low (red)
PROBLEM (SOLUTION)

  • Incorrect attenuation at LO1 (Adjust Pwr (dbm) value if set manually).

  • Incorrect sky frequency for receiver selected (Select correct frequency_).

  • LO has reset itself back to default values (sky frequency=1234). (Reset with correct parameters. Also check all other parameters).


SYMPTOM: No LO Power at receiver
PROBLEM (SOLUTION)

  • Receiver not selected or routed properly on LO1 (Check for proper selection/routing).

  • Power insufficient due to filter selection (Check or change filter at receiver).

  • Receiver manager in OFF state (Turn ON).


SYMPTOM: Noise source calibration signal not firing
PROBLEM (SOLUTION)

  • Wrong device controlling calibration (Check switch signal selector settings).


SYMPTOM: Cryogenic temperatures (Kelvin) rising
PROBLEM (SOLUTION)

  • Cryogenics set to off (Call maintenance. Set to cooling).

  • Cryogenics compressor failing (Check compressor supply/return readings for nominal values).

  • Helium pressure low (Lines may require recharging; call maintenance).


SYMPTOM: LO1 Manager, Accessor, or Transporter showing fault (red)
PROBLEM (SOLUTION)

  • Loss of YGOR Manager, Accessor, and/or Transporter (Reset via reset box (gbtaio1, gbtaio2) or TaskMaster command).


SYMPTOM: RFI spikes in continuum data every 12 seconds when using L-band
PROBLEM (SOLUTION)

  • Notch Filter is not turned on or malfunctioning (Cycle OFF then ON and recheck data).


SYMPTOM: IF Rack RF power low
PROBLEM (SOLUTION)

  • Wrong filter selected (Check/select filter compatible with receiver).

  • Laser power to optical receiver channel is off (Turn on).


Backends

DCR


SYMPTOM: No values in sampler columns or values not updating/correct
PROBLEM (SOLUTION)

  • Loss of YGOR Manager, Accessor, and/or Transporter (Reset via reset box (gbtdcr) or TaskMaster command).

  • Signals not routed correctly (Check via Device Explorer application).

  • Not set as the switching signals master (Launch Switch Signals Selector and check/set DCR as switching source).

  • Internal software communication failure (Try to correct by changing phase table settings via Scan Coordinator followed by a "prepare").


SYMPTOM: Difficulty connecting with the device
PROBLEM (SOLUTION)

  • Accessor has lost contact with the device's singleboard computer (Reset via reset box, TaskMaster commands, or other current guidance).


SYMPTOM: Hung in state (committing, activating, or running)
PROBLEM (SOLUTION)

  • DCRServer on vortex hung in state shown (Possible fixes: Aborting observation via the Scan Coordinator. Reboot the DCR via the reset box. Stop/restart process via TaskMaster commands).


-- DavidRose - 27 Mar 2007

Topic TroubleShootingGuide . { Edit | Attach | Ref-By | Printable | Diffs | r1.4 | > | r1.3 | > | r1.2 | More }
Revision r1.4 - 27 Mar 2007 - 16:04 GMT - DavidRose
Parents: WebHome > TelescopeOperations
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