• Topic ID: id_13106462
  • Version: 4.1
  • Date: Mar 4, 2020 4:18:32 PM

MNS Troubleshooting

Table 1 Personnel requirements
Required persons Preliminary requirements Procedure Finalization
1 - - -
Table 2 Tools and test equipment
Item Quantity Effectivity Part number Manufacturer
RF Power Measurement Kit (use one of the following): 1 -

5307511-2 or 5307511-3 (Bird wattmeter)

 -

This document applies to both the AMT amplifier and the CPC amplifier.

This document contains possible error messages and faults due to the multi-nuclear spectroscopy (MNS) radio frequency (RF) receive and transmit chains.

Interconnect diagrams for MNS subsystem are available under the System Diagrams folder, Interactive Block Diagrams, then by choosing the RF > MNS Option view.

note:

Remove the multi-nuclear spectroscopy transmit/receive (MNS T/R) module from the system when the spectroscopy scanning is complete. The presence of the module may cause image quality degradation.

Troubleshooting Receive Chain

Problem: No receive signal; no noise on the prescan screen
  1. Verify that the proper center frequency is being used for either carbon or phosphorous nucleus. Check the switch and determine what type of switch it is.
    Table 3 3.0T MNS Frequency Range
    Nucleus Minimum Frequency Maximum Frequency
    13C 32.016 32.227
    31P 51.574 51.941
  2. Confirm that you can perform a TPS reset without MNS receive errors.
    1. If so, check the connection between J4 and the LPCA. If the connection is working properly, connect the narrow band coil to the A-port connector and perform a test scan. If the connection is not working properly, fix the connection.
      1. note:
        If the test scan passes, inspect the MNS quick disconnect box for damage. Confirm with the customer that the coil is in working order or run the MNS Functional Check procedure.

        • If the functional check fails, the MNS T/R switch has failed or the quick disconnect box is faulty.

        • If the functional check passes, but there is no signal, ensure that the 8W8 cable assembly from the LPCA is plugged into J4 of the MNS upconverter

      2. If the test scan fails or the system cannot scan, inspect the A-port connector, ODU egress connector for damage. Also check that the RF amplifier is producing the proper RF output power.
    2. If the TPS reset fails, check these connections at the MNS upconverter and confirm that each is in working order:

      • Upconverter J5 to reroute box (RRB) J8

      • Upconverter J2 to RF control board J11

      • Upconverter J1 to SPW J33

      • SPW J33 to MNS exciter J2

      • SPW J31 to MNS exciter J1

      If the connections are working properly, check the operation of the MNS upconverter. If the connections are faulty, fix the connection that needs repair.

Problem: Multiple spurs in the MNS noise tests, spaced apart about 60 kHz apart
  1. At the PEN wall, check all the cabling coming from the PHPS2. In particular, check the quality of the contacts and shielding.
  2. Check the in-line filters (if any) and toroids (if any).
Problem: Single spur in the 13C MNS noise test
  1. Check that the magnet pressure transducer is properly shielded.
  2. Confirm that the SRI firmware is at the latest revision. Check the SRI cabling for good contact and shielding.

Troubleshooting Transmit Chain

Problem: Transmit is malfunctioning
  1. Measure the amplifier output source by connecting the RF output to the RF power meter.

    For details, see 8kW 3.0T MNS Amplifier Calibration.

    Click here for the Bird 3.0T RF Power Measurement Kit (Wattmeter Kit) 5307511 operator manual. 2043065.pdf

    Figure 1. MNS Output Test Setup Using Bird 3.0T RF Power Measurement Kit

  2. If there is a TR bias issue, check the MNS T/R switch. Use a multimeter in the diode drop mode (open in one direction, 0.4 V in the other direction) to ensure that the MNS T/R switch is working properly.

    Figure 2. MNS T/R Switch Diode Check

    Ensure that the T/R bias path is complete from the bias driver module in the PEN cabinet to the T/R switch on the LPCA cover.

    Locate the switch arrangement on the SPW and ensure that the switches are properly connected.

    Figure 3. SPW Transmit Switch Locations

Problem: There is no signal; transmit signal is out of specification
  1. Ensure that the amplitude of the RF transmit pulse at the input of the RF amplifier by disconnecting the cable at the RF IN port on the amplifier and connecting it to the 50 ohm DC input of an oscilloscope, with a DC block.
  2. Run a test scan. The amplitude of the square pulse should be >0.2 V peak-to-peak at a TG setting of 200.
Problem: Reflected power on RF amplifier is high (>50% of forward power)
  1. Attach the dummy load to the RF output.
  2. If the problem is corrected, check the transmit chain connection and other components (T/R switch, coil).
Problem: UPM sense fault; UPM sense light and/or inhibit light constantly illuminated
  1. Check connections to RF amplifier. Refer to Interactive Block Diagrams.
  2. Systematically swap the circuit boards inside the ASC chassis, noting whether the error follows one particular board.
  3. Swap the connections from the amplifier to the boards in the ASC to see if this indicates a problem coming from the amplifier.
  4. If there is an issue coming from one particular component (UPM RF detector boards, UPM processor boards, RF amplifier, 50 ohm terminators), investigate the issue to ensure that component is working properly with the system.
Problem: Receiving UPM errors at the operator workstation, “spectro amp not ready”
  1. The 50 ohm terminators may not be connected. Check that the 50 ohm loads (BNC male snap-on) are applied to J1, J2, J3, and J6 on UPM RF detector boards 19U and 19L. Ensure UPM cables are connected to J4 and J5 on UPM RF detector boards 19U and 19L.
  2. If the connections are okay, ensure the UPM RF detector boards and 50 ohm terminators are working properly.