Gradient Filter Replacement

Prerequisites

Table 1 Personnel requirements
Required persons	Preliminary requirements	Procedure	Finalization
1	Not Applicable	30 minutes	Not Applicable

Table 2 Tools and test equipment
Item	Quantity	Effectivity	Part number	Manufacturer
Digital volt meter (DVM) with alligator clip leads	1	-	-	-
Non-ferrous tool kit	1	-		-

Table 3 Replacement parts
Item	Quantity	Effectivity	Part number	Manufacturer
Gradient Filter Assembly	1	-	See FRU manual	-

Table 4 Safety

FATAL ELECTRIC SHOCK HAZARD!
THE GRADIENT Amplifiers ARE CONSTANT CURRENT SOURCES AND WILL SEND maximum CURRENT TO ANY LOAD including any person touching the gradient filter connectors.
TO PREVENT FATAL ELECTRIC SHOCK, ENSURE THAT POWER IS OFF TO the gradient subsystem before CONTINUING WITH THIS PROCEDURE.

Potential Projectile Hazard!
ferrous materials can become dangerous projectiles in the presence of the magnetic field produced by the magnet.
Do not bring any ferromagnetic tools or equipment into the magnet room.

Overview

The gradient filter attaches to the secondary pen wall (SPW) from the equipment room. The thumbscrews on the filter attach to PEM nuts on the SPW.

FATAL ELECTRIC SHOCK HAZARD!
THE GRADIENT Amplifiers ARE CONSTANT CURRENT SOURCES AND WILL SEND maximum CURRENT TO ANY LOAD, including any person touching the gradient filter connectors.
TO PREVENT FATAL ELECTRIC SHOCK, ENSURE THAT POWER IS OFF TO the gradient subsystem before CONTINUING WITH THIS PROCEDURE.

Potential Projectile Hazard!
ferrous materials can become dangerous projectiles in the presence of the magnetic field produced by the magnet.
Do not bring any ferromagnetic tools or equipment into the magnet room.

From the scan room side of the gradient filter, remove the plastic gradient filter terminal covers.

Figure 1. XRMB Gradient Filter

note:
Two wrench technique: Use two wrenches when removing the cables from the gradient input/output connectors on each side of the SPW. One wrench prevents the post from turning, while the other loosens the nut. If you try to loosen the nut with only one wrench, the post itself could turn and damage the gradient filter.
Remove the cables attached to the terminals in the scan room.
From the equipment room side of the gradient filter, remove the plastic gradient filter terminal covers and remove the terminal cables. Use the two wrench technique to remove the cables.
While in the equipment room at the SPW, remove the screws securing the gradient filter assembly to the SPW panel.

Remove the gradient filter and set aside.

Figure 2. Gradient Filter Thumbscrews

Lift the gradient filter onto the guide pins on the SPW and tighten the thumb screws. When done, use a screwdriver to tighten.
Attach the cables to the gradient filter connections on both sides of the filter. Start with the GND, Z-axis, Y-axis, and X-axis cables and ground wires. Snugly tighten each cap nut to attach the correct axis cable to the correct gradient filter connection. The lug connections between axis and polarities should not be touching.

Figure 3. Gradient Terminals

note:
Red cable indicates positive (+) wires, black cables indicate negative (-) wires.

Two wrench technique: Use two wrenches when attaching the cables from the gradient input/output connectors on each side of the SPW. One wrench prevents the post from turning, while the other tightens the nut. If you try to tighten the nut with only one wrench, the post itself could turn and damage the gradient filter.

note:
Make sure to tighten each cable as you attach it, because you cannot reach all cables after attaching them.
Tighten the cap nuts and verify that nuts are not loose.

Verify that all connections are tight, correct, and not touching each other. Make sure each screw is fixed, each nut is tight, and each cable is not detached from terminal.

Figure 4. Cables Connected
Replace the plastic gradient filter terminal covers.
Remove LOTO from the PGR cabinet. See the MR Service Safety Manual, PN 5452735.

Run the DQA II tool to verify proper gradient polarities. See DQA II Tool and Troubleshooting.