Discovery MR750 3.0T System Service Methods
5690009-2EN Revision 4
Object ID: 00000018WIA30FBD030GYZ
Topic ID: id_12374006 Version: 1.5
Date: Jul 5, 2019 10:24:08 PM

eXtreme Gradient Amplifier Replacement

Prerequisites

Table 1. Personnel requirements
Required persons	Preliminary requirements	Procedure	Finalization
1	5 minutes	75 minutes	5 minutes

Table 2. Tools and test equipment
Item	Quantity	Effectivity	Part number	Manufacturer
Hoist Service Kit	1	-	5196226	-
Non-Magnetic Tool Kit (or equivalent)	1	-	5113258	-

Table 3. Consumables
Item	Quantity	Effectivity	Part number	Manufacturer
Towels	N/A	-	-	-
Nitrile Gloves	As needed	-	-	-

Table 4. Replacement parts
Item	Quantity	Effectivity	Part number	Manufacturer
XGA unit	1	systems with XGA units	See FRU manual.	-
XG2 unit	1	systems with XG2 units	See FRU manual.	-

Table 5. Safety

DANGER

Electric Shock Hazard!

High voltages are present in the PGR cabinet.

Perform LOTO on the PGR cabinet. See the “mr service safety Manual,” PN 5452735.

Warning

possible personal injury or equipment damage!

the module could fall when using the lift tool.

before putting weight on the hoist chain, be sure that the links are aligned properly. this helps keep the chain from binding up, or becoming kinked, which is nearly impossible to correct when the chain is under tension.

Warning

Laser Radiation Hazard!

Invisible laser radiation can be emitted from disconnected fiber-optic cables or connectors.

Do not stare into the beam, point the cable or connector ends at your eyes, or view through optical instruments.

Notice

Electrostatic discharge (ESD) can cause permanent damage to electronic components. Observe the following ESD precautions:

Wear a static wrist strap to ensure that any accumulated electrostatic charge is discharged from your body to the ground.
Create a common ground for the equipment being worked on by connecting the static-free mat, static wrist strap, and peripheral units to that piece of equipment.

Notice

The SFP optical transceiver is very sensitive to ESD. SFP latent failures can occur, in dry climates or low relative humidity, surpassing their ESD protection.

Contaminant failures can occur in SFP optics and exposed glass Rx and Tx cable ends. Do not touch the exposed ends on fiber connectors. Leave the dust caps in place until you are ready to install the SFP module. Use the Fiber Optics Cleaning Kit to clean both the SFP and cable end every time they are replaced or swapped from one port to another, or when using a loopback.

For more information on handling and cleaning the SFP transceiver refer to Fiber Optic Cable Devices Installation and Replacement.

Notice

When working with the SFP optical transceiver or SFP Loopback, also observe the following precautions:

Always use ESD protection when handling the SFP optical transceiver to prevent early failure.
Always keep a protective cap on unplugged fiber connections.
The SFP must be shipped in antistatic packaging. Discard any SFP shipped or stored without proper ESD protection.

Table 6. Required conditions
Condition	Reference	Effectivity
The power in the cabinet needs to be off. Perform LOTO on the PGR cabinet before the XGA unit is replaced. See the MR Service Safety Manual, PN 5452735.	-	-
Before disconnecting any cables on the front of the XGA unit, shut down the PPMP at the HEC. Press `▲ F3` simultaneously to stop the pump. Then switch the PPMP circuit breaker to OFF.	-	-

About this task

Overview

This procedure explains how to replace an eXtreme Gradient Amplifier (XGA) unit in the PGR cabinet. This unit weighs about 200 pounds so a hoist kit is required. This procedure details the correct way to safely use a hoist kit to remove the XGA unit and replace it with a new XGA.

Note:

The system contains either XGA or XG2. These units have the same form factors, but are not interchangeable (a system has either all XGA or all XG2 units). Make sure you order the correct FRU for the system.

This procedure refers to both units as XGA units (except where a distinction needs to be made).

Procedure

DANGER

Electric Shock Hazard!

High voltages are present in the PGR cabinet.

Perform LOTO on the PGR cabinet. See the “mr service safety Manual,” PN 5452735.

Perform LOTO on the PGR cabinet before the XGA unit is replaced. See the MR Service Safety Manual, PN 5452735.

Before setting up the hoist kit, remove the XPS J9 connector to properly remove the main lifting beam.

Figure 1. Lifting Beam and Connector in PGR Cabinet
See Hoist Service Kit and Lifting Accessories to set up and secure the hoist.
Turn off the pump according to directions in Required Conditions above.

When the pump is off, the drive display will show “- - -”.
Note:
For the next step, wear nitrile gloves. Be prepared to absorb any leakage from the coolant lines with a towel in hand as the line is disconnected.

Turn off the pump breaker, and then disconnect the cables and hoses from the front of the XGA unit. This includes the XPS to XGA power cables, the coolant lines, and the fiber optic cables.

Note:
Do not bend the fiber optic cables. These are very delicate cables and can break easily.

Figure 2. Front of XGA Unit: Cables Connected
Unscrew the two screws from the bottom module retaining bracket of the XGA unit. They are captive screws and do not fully detach from the bracket.
When the XGA is extended out and you have access to the three screws, remove the module retaining bracket and set it aside. You will need this module retaining bracket for the FRU.

Figure 3. Module Retaining Bracket

Note:
If replacing the X-axis XGA unit, you may need to remove the PGR cabinet door and lean it to the side of the cabinet. Use tape to secure the free end of the green/yellow ground wire detached from the upper part of left door to the PGR cabinet frame, so it cannot inadvertently contact any of the incoming L1, L2, or L3 AC mains power connections in the terminal strip in the upper left PGR cabinet.
Remove the nuts on the plus and minus connectors of the gradient amplifier. Slide it out partially, if necessary. Use two wrenches to disconnect the cables.

Figure 4. PGR Cabinet - Plus and Minus Connectors
Place the lifting bracket from the FRU crate on top of the XGA. The attachment screws are stored on the bracket. Match the four openings and screw in the lifting bracket.

Use a washer with each attachment screw.

Figure 5. Lifting Bracket
Hook the winch from the hoist kit to the lifting bracket. Ratchet the winch to tighten the chain.

Figure 6. XGA Unit Connected to Hoist Kit

Note:
Make sure the hook is seated in the lifting bracket. If not, the weight can shift and cause harm to the equipment or the engineer.
With the XGA unit being held by the slide rails and the hoist kit, it is now secure enough to extend the unit until the slide rails lock. Press the release tabs in on each side as you pull the unit out further.

Figure 7. XGA Unit Extended out of Cabinet
Push the release mechanism on the back end of the outer slide rail to release the outer rail. The cabinet rails are a reverse image of each other.

You may want to use a screwdriver to release the outer slide rail.

Figure 8. Slide Rail Latch Release
After the unit is removed from the outer rails, slide the outer rails into the cabinet.
The FRU is packaged in a wooden crate. Remove the top of the wooden crate and turn it on its wheels. The XGA unit being removed can be placed into the top. Roll the top under the XGA unit. Lock the wheels so that the container does not move.

Figure 9. FRU Package
Ratchet the winch to lower the XGA unit into the package.
After it is lowered, unscrew side rails from both sides of the XGA unit.
Remove the hook from the lifting bracket.
Unscrew the lifting bracket from the top of the unit. Roll the removed XGA unit to the side.

Note:
The old XGA must be purged of water coolant before being returned to prevent freeze damage during shipment. Do not seal the box before purging XGA coolant as described in Finalization.
Remove the center section of the FRU crate and set it aside. This is used to package the old XGA unit.
Bring the new unit to the front of the cabinet. Connect the slide rails to the new unit.

Figure 10. XGA FRU
Screw the lifting bracket to the top of the new unit.
Hook the new XGA unit to the hoist kit.

Note:
Make sure the hook is seated in the lifting bracket. If not, the weight can shift causing harm to the equipment or the engineer.
Ratchet the winch to tighten the chains and begin lifting the unit. Slide out the rail a short amount to see how high to lift the new XGA unit. The slide rails of the XGA unit and cabinet must align for correct insertion.
When the slide rails are aligned, pull the slide rails out a short distance to get each side started. After both of the slide rails are attached, pull the slide rails on to the FRU until you hear a click, indicating that the unit is docked in the rails.
Attach the module retaining bracket to the XGA unit.
Ensure the XGA unit is secure on the rails and slightly loosen the chains with the winch to allow some freedom of movement. Press in both release tabs and begin to slide the XGA unit in until only the top of the unit is exposed.
Unhook the hoist kit from the lifting bracket. Remove the lifting bracket from the top of the new XGA unit.

Place the lifting bracket into the XGA FRU crate with the four screws attached to the lifting bracket.
Attach the J17 minus cable and the J18 plus cable using two wrenches. (See Figure 4.)
Tighten the module retaining bracket to the PGR cabinet.
Connect cables and hose connections to the new unit.

Note:
If you are installing a new XGA unit (not an XG2), the dual fiber optic cable may be difficult to reinsert into the new XGA unit. (The connector for the XG2 has been designed to eliminate this issue.)

Do not remove the SPF module from the XGA unit.

To connect the fiber optic cable, insert the dual fiber optic cable into the SPF module in the XGA by gripping either side of the hard plastic connector housing at the black section and then firmly pushing the connector into the SPF module until the connector clicks into place. Do not grip the molded plastic boot sections where the fiber optic cables enter the connector.

If the cable is inserted backwards, it will not go in all the way.
Disassemble the hoist kit (see Hoist Service Kit and Lifting Accessories).
Return the main lifting beam to the PGR cabinet. After the beam is secure, reconnect the XPS J9 connector. Return the support tube to the HEC.

Finalization

Remove LOTO from the PGR cabinet. See the MR Service Safety Manual, PN 5452735.
Turn on the PPMP circuit breaker at the HEC. Start the pump by pressing ▲ F3 simultaneously.
Verify that the pump has started by checking that the drive frequency display shows a value.
Run the DQA II tool to verify proper gradient polarities and adjust gradient calibration. (See DQA II Tool and Troubleshooting.)
Recommended: Perform a SaveInfo to capture new gradient calibration values.
Remove coolant from the XGA unit being returned using the manual coolant removal kit included with the HEC. (See Coolant Draining.)
Dispose of used towels according to local disposal standards.
Attach the center of the FRU package to the removed FRU unit base. Then attach the top of the FRU crate to prepare the FRU for return.