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123T Antenna Control System with 2.4M SMLT Antenna
Field Troubleshooting Guide
1. ACU will not boot or keeps resetting.
Likely problem – Hardware failure inside the ACU
Troubleshooting tips –
1. Verify power input is 90-264VAC, 47-63 Hz.
2. Disconnect all external connections to the ACU except the power input cord.
3. If problem persists, send ACU back for repair.
4. If the ambient temp is below 0 deg C, you will see a “Warm Up” light on the front panel that indicates that the ACU heaters are on and the processor is held in Reset. It can take up to 20 minutes for the system to boot depending upon the ambient temperature.
2. Antenna will not stow.
During STOW, the EL Down limit is overridden.
The control overrides the EL DN limit for STOW, but only if two conditions are reached.
1. AZ Stow Align must occur. This is an external switch the control reads.
2. POL Stowed must occur. This is an external switch (or feed jumper) the control reads.
All Circular feeds have a jumper permanently installed (in the feed) to generate the required POL Stowed interlock.
All Linear feeds generate POL Stowed when the feed is driven to the CCW limit.
If no feed is installed then you have to connect a special plug at the Feed connector. This plug has one wire, and this wire generates the POL Stowed interlock
You can go to the ACU's Messages>Status Messages menu to see if AZ STOW ALIGNED and POL STOWED conditions have occurred.
Troubleshooting tips –
1. Verify AZ is driven to the stow angle and AZ STOW aligned status message occurs.
2. Verify POL is driven to the POL STOWED angle and the POL STOWED status message occurs.
3. Verify EL slows to 1/10th speed about 4 degrees before final stow position. If not, EL Velocity limit switch may need adjustment.
4. If EL Velocity limit occurs too soon, the antenna may stop before it reaches the stow pads – Message “Stow Incomplete” will occur.
5. Replace PDU with known-good unit.
3. Antenna runs faster than normal - AZ or EL - will not hold position.
Symptoms – Antenna runs one direction only. Antenna runs faster than normal. Antenna will not hold position - Runs one direction (continuously) when attempting to hold a preset position.
Usually a problem in the speed control loop -
1. Can be a problem in the PDU.
2. Can be a problem with tachometer scaling (this is a setting stored in the ACU's memory)
3. Can be an external antenna wiring problem - Bad connection to the motor tachometer.
4. Can be a problem with the motor itself - Bad tachometer.
Best way to troubleshoot this type of problem in the field is to:
5. Replace the PDU. - Problem gone, fault was in the PDU.
6. Replace the ACU. - Problem gone, fault was tachometer scaling in the ACU - Edit the ACU parameters to fix.
7. Five and Six above are not the problem, then problem is either 3) or 4) above. Continue troubleshooting antenna/motor with voltmeter.
If problem persists check continuity from PDU connector J8 to the motor tachometer. If continuity looks good then replace the motor.
4. Antenna will not move AZ (EL)
Possible problems:
1. Bad motor
2. Bad PDU.
3. AZ (EL) fault.
4. System-Level Fault.
5. Bad connection to the motor.
6. Band Select Fault
Troubleshooting Tips:
1. Check the ACU’s fault messages – Eliminate all motor disabling faults (ACU E-stop, Antenna E-Stop, Handcrank faults, etc.).
2. Eliminate the “Band Select” fault. This is a disabling fault and occurs when the frequency entered does not match the detected feed type.
3. Replace the PDU with a known-good spare.
4. Continuity check from PDU connector J8 to each motor.
5. Voltage check at the motor.
5. Antenna will not move POL.
Possible problems:
1. Bad motor
2. Bad PDU.
3. POL fault.
4. System-Level Fault.
5. Bad connection to the motor.
6. Band Select Fault
6. ACU - PDU serial link down fault and Compass Link down fault.
Anytime the “ACU-PDU serial link down” fault occurs, the “Compass Link down” fault will also occur. Compass data is passed from the PDU to the ACU over the ACU-PDU serial link.
Fixing the “ACU-PDU serial link down” fault is the correct troubleshooting step.
Possible problems:
1. Bad ACU-PDU serial link cable.
2. Bad ACU.
3. Bad PDU.
Troubleshooting Tips:
1. Run continuity test on the ACU-PDU serial link cable.
2. Replace the ACU with a known-good unit.
3. Replace the PDU with a known-good unit.
7. System will not find satellite.
Possible problems:
1. Antenna is not pointed at the satellite.
2. RF failure in the receive chain.
3. ACU setup problem.
4. ACU tracking receiver problem.
Troubleshooting Tips:
1. Verify the correct beacon frequency setting.
2. Verify the correct satellite longitude.
3. Verify the Low Signal threshold setting ( FREQUENCY menu ) is 4-5 dB above the sky’s noise floor.
4. Check the Box Scan size ( SETUP >TRACK SETUP menu). Increase to 12 degrees if necessary.
5. Apply L-Band signal to the ACU’s tracking receiver input. Verify signal level displayed at the ACU frontpanel equals the signal generator output (dBm) when the ACU signal offset ( FREQUENCY menu) is set to -56 dB.
6. Check the receive signal path back to the feed. Replace the feed pallet if necessary.
7. See “Deployed AZ heading does not make sense” section for additional troubleshooting items (bad pointing angle).
8. Multiple faults occuring at the ACU - AZ CW Prelimit, AZ CCW Prelimit,
EL UP Prelimit and EL DN Prelimit.
The 123T PDU supplies +12VDC to each limit switch. Limit switches are typically wired in groups, sourced from a common +12VDC wire. Loss of this common +12VDC source can cause multiple fault messages.
Symptoms: Multiple AZ/EL/POL limit faults at the ACU preventing most antenna functions.
Possible problems:
1. Bad PDU.
2. Short in external antenna wiring (+12VDC to Gnd).
3. Open in external antenna wiring (+12VDC).
Troubleshooting Tips:
1. Replace PDU with known-good unit.
2. Check antenna wiring harness for short circuit, +12VDC to GND.
3. Check antenna wiring harness for open circuit, +12VDC.
9. ACU displays “Band Conflict” Fault.
Symptoms: Band Conflict fault disables AZ, EL, and POL operation.
"Band Conflict" occurs when the detected feed type does not match the carrier frequency entered at the ACU’s “Frequency” menu.
Example - The system detects Ka feed but the operator has entered a Ku frequency - This will generate a "Band Conflict" fault.
Troubleshooting Tips:
1. Check the frequency entered at the ACU’s menu. Verify this matches the feed type indicated at the menu
2. If the feed type indicated at menu does not match the actual feed installed then the problem might be in the feed itself. There are one to three jumpers in the feed that tell the Antenna control the feed type. One of these jumpers can be missing or have a bad connection. Install the same feed from another trailer. If the problem goes away then there is a feed-type jumper problem inside the feed.
3. If the problem persists then ohm the feed-type connections between the feed and the PDU.
4. If the problem persists then replace the PDU with a known-good spare.
10. Deployed AZ heading does not make sense.
Symptoms: Antenna cannot find the satellite or satellite found with large AZ error.
The 123T control applies AZ pointing angle corrections immediately upon execution of “DEPLOY”. All the sensor data is read – GPS, Tilt, and Compass. Failure of any sensor can lead to AZ pointing angle errors.
NOTE: The electronic compass is a sensitive detector of the earth’s relatively weak magnetic field. As such, this device usually is the largest source of AZ heading errors.
Possible problems:
1. Bad tilt sensor data.
2. Bad Compass data.
3. Bad GPS data.
4. Bad Compass Mark Angle setting.
5. Bad compass environment ( local buildings, trucks, electrical noise, metal near the compass ).
Troubleshooting Tips:
1. Verify GPS Quality is 1 (or greater) before executing DEPLOY mode. You can see this parameter at the SETUP>CALIBRATE menu. GPS Quality less than 1 will generate the “Calibration Fail” fault upon deploy. Lack of correct GPS data can result in a bad MAGNETIC VARIANCE offset.
2. Check GPS antenna – Verify coax connection to the ACU. Verify GPS antenna has clear view of the sky.
3. Using the trailer jacks, level the trailer and cross-check with a bubble level. Go to the SETUP>CALIBRATE menu and read the F/B and R/L tilt data. These should make sense – approx zero with trailer bubble leveled. Bad Tilt data can cause both AZ and EL pointing angle errors.
4. With the antenna stowed, sight the trailer’s centerline with a hand-held “needle” type compass. Compare this against the compass angle data at the SETUP>CALIBRATE menu. If the data does not match, correct with the SETUP>CALIBRATE>COMPASS MARK ANGLE parameter.
5. The Compass Mark Angle is operator selectable and is used to compensate for compass mounting errors and static compass errors. This parameter is normally zero. Any number greater than +/-3 degrees can indicate a bad compass mount or a bad compass calibration.
6. The compass is only accurate when level, +/- 15 degs. After the dish has deployed the compass is no longer level and the compass angle is displayed but not used. All compass accuracy tests should be performed with the dish stowed.
7. With the antenna stowed, monitor the compass output at the SETUP>CALIBRATE menu. Watch the output for 1-2 minutes and note any jumps or stability problems. The compass is an extremely sensitive device and can pick up electrical / magnetic noise from the surrounding environment (any electrical device).
8. With a hand-held “needle” type compass, walk around the trailer to see if the “North” angle makes sense. Objects around the antenna (buildings, trucks, etc.) can bend the earth’s magnetic field, producing local distortions. Locate the hand-held “needle” type compass on top of the antenna’s electronic compass. Any “strange” behavior observed by the hand-held compass will also be seen by the electronic compass.
11. ACU displays "Calibration Fail" fault.
Symptoms: Upon executing DEPLOY mode the "Calibration Fail" fault occurs.
Possible problems:
1. Bad Compass data.
2. Bad GPS data.
Troubleshooting Tips:
1. Verify GPS Quality is 1 (or greater) before executing DEPLOY mode. You can see this parameter at the SETUP>CALIBRATE menu. GPS Quality less than 1 will generate the “Calibration Fail” fault upon deploy. Lack of correct GPS data can result in a bad MAGNETIC VARIANCE offset.
2. If GPS Quality of 1 (or greater) cannot be achieved, check the GPS antenna – Verify coax connection to the ACU. Verify GPS antenna has clear view of the sky.
3. Check for ACU-GPS serial link fault. If present, replace the ACU.
4. Check for COMPASS LINK DOWN fault. If present, fault is caused by bad PDU or bad compass or bad compass wiring. Replace PDU with known-good unit. If problem persists then replace compass. Compass failure may be in the cable connector.
12. AZ (or EL) position feedback will not change or jumps.
Symptoms: AZ (or EL) position feedback does not change when driving the antenna.
Symptoms: AZ (or EL) position feedback is not stable – Position jumps or rolls.
Possible problems:
1. ACU setup problem – Wrong encoder type.
2. PDU failure.
3. Open-circuit or short-circuit on Resolver signals.
4. J9 / J11 resolver connectors are not seated properly at the PDU.
5. Resolver has failed.
Troubleshooting Tips:
1. Re-seat the PDU’s J9 / J11 resolver connectors.
2. Replace the PDU with a known-good unit. If the problem goes away then return the PDU for repair.
3. Replace the ACU with a known-good unit. If the problem goes away then check the encoder type settings at the ACU’s SETUP>AZ SETUP and SETUP>EL SETUP menu’s.
4. Continuity check the AZ and EL resolver reference wiring – Look for open-circuit or short-circuit on Resolver signals.
13. Compass-Link Down Fault.
Possible problems:
1. ACU-PDU serial link fault will also cause the Compass link down fault. Fix the problem by troubleshooting the ACU-PDU serial link fault.
2. Bad PDU.
3. Bad Compass.
4. Bad Compass wiring.
Troubleshooting Tips:
1. See ACU - PDU serial link down fault and Compass Link down fault troubleshooting section.
2. Replace the PDU with known-good unit.
3. Check all connections between the compass and the PDU.
4. Replace the compass.
5. Open the compass connector(s) and inspect for opens / shorts.
14. Compass has 60 to 90 degree error.
The KVH C100 fluxgate compass has internal memory used to store calibration data. If this memory becomes corrupted then the compass can have a large (60-90) degree offset error. This error cannot be removed by executing “Compass Calibrate” mode from the SETUP>CALIBRATE Menu.
Troubleshooting Tips:
1. Try executing “Compass Calibrate” mode from the SETUP>CALIBRATE Menu. (See Compass Calibration procedure).
2. If problem persists then replace the compass.
15. ACU displays “Axis Difference” fault.
The 123T PDU has redundant fault sensing circuitry. Axis difference fault indicates one fault circuit indicates "OK" and the second (redundant) fault circuit indicates "FAULT".
The Axis difference fault (by itself) does not disable motors, but there is (almost) always an associated fault, and usually the associated fault disables some motor or function.
All the redundant fault sensing circuitry is internal to the PDU.
Troubleshooting Tips:
1. Replace the PDU. Field repair is not possible.
16. ACU displays “AZ CW Prelimit” and “AZ CCW Prelimit” faults.
The AZ limits normally occur anytime the dish drives into the EL Down limit. This is by design and is intended to prevent damage to the feed boom.
During STOW, the EL Down limit is overridden.
If (during stow) the EL Dn Limit is not Overridden then you will get EL DN + AZ CW + AZ CCW limits. Driving UP will clear the AZ and EL Limits.
So, the question is, why is the EL DN limit not being overridden (during stow). See troubleshooting procedure “Antenna will not Stow” for more help.
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