PRM-470 NHA-472 Board Replacement

Press and hold the POWER button until instrument powers off.

Use a medium Phillips (PH2) screwdriver. Screws do not need to be completely removed.

Battery connection is labeled 1.

Remove connectors at locations 5, 6, and 7.

Gently pry up each side and lift.

Verify connectors are correctly aligned then press down.

Do not connect location 1.

To access the neutron detector information, remove the moderator from the case and slide the neutron detector out.

Detector information is printed on the detector. There are two (2) common neutron detector manufacturers: GE Reuter-Stokes and LND. RS indicates GE Reuter-Stokes.

Press POWER button until the display turns on.

Use Fluke 80K-40 High Voltage Probe and Fluke 179 DMM. The GND tab should line up with the COM position.

The neutron ground TP38 is located on the NHA-472 neutron board and might not be clearly labeled.

The ground connector for the HV probe may be directly connected to the ground test point.

It may be easier to use a separate test lead (jumper wire) and connect the HV probe ground to the test lead.

The neutron high voltage TP34 is located on the NHA-472 neutron board and might not be clearly labeled.

Contact TP34 (not labeled) with tip of red HV probe.

R10 on the NHA-472 neutron board is used to adjust the high voltage for the neutron detector.

Use precision slotted (tweaker) screwdriver to adjust R10. The voltage should match the manufacturer’s recommendation.

GE Reuter-Stokes: 990 Volts

LND: 1075 Volts

The number indicated on the DMM must be multiplied by 1000 if the Fluke 80K-40 probe is being used.

R17 on the NHA-472 neutron board is used to adjust the stage 2 gain.

Use precision slotted (tweaker) screwdriver to rotate R17 10 full turns clockwise.

Use a medium Phillips (PH2) screwdriver.

Record observations, times, and results for the maintenance report.

As specified by management or contractual obligations.