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 | Caution This procedure is recommended for experienced technicians and engineers only. Before beginning this procedure, it is strongly advised that you read through the entire document. If you have any doubts about your ability to perform any part of this procedure, please contact your nearest service representative for further guidance. |
 | Warning Turn off power to the chassis and unplug the power cord before accessing the chassis interior and removing any cards. Use extreme caution around the chassis since potentially harmful voltages are present. |
The replacement part for this procedure is the MAS-26 175 watt power supply. The MAS-26 is recommended for use in the M chassis.
This power supply must operate with 240 volt alternating current (VAC) source input, and provides direct current (DC) output voltages of +/- 5 volts and +/- 12 volts.
Electrostatic discharge damage (ESD) occurs when electronic printed circuit cards are improperly handled and can result in complete or intermittent failures. ESD can impair electronic circuitry and equipment. Always follow ESD prevention procedures when removing and replacing cards.
Following are steps for handling printed circuit cards:
Step 2: Connect the strap to an unpainted chassis frame surface or another proper grounding point or surface to safely channel unwanted ESD voltages to ground (see Figure 1).
Step 3: Use the ejectors to remove the card. Handle the card by its sides. Place the card on an antistatic surface or in a static shielding bag. To prevent further damage to the card by ESD voltages, defective cards must remain in the static shielding bag when returned for repair or replacement.
Step 4: Handling the new card by its edges only, insert it into the chassis. Avoid contact between the card and clothing. The wrist strap only protects the card from ESD voltages on the body; ESD voltages on clothing can still damage the card.
Use an ohmmeter to check the ESD wrist strap to ensure that the resistor is providing proper ESD protection. For safety, the measurement should be in the range of 1 to 10 Mohms.
Refer to the following procedures and accompanying illustrations to access and remove the suspect power supply and to install the new MAS-26 power supply. Before you start the installation procedure, read through this entire document to familiarize yourself with the required tasks.
 | Warning Turn off power to the chassis, and unplug the power cord, before gaining access to the chassis interior and removing any cards. High voltages may exist in or near the power supply. Use extreme caution when working with the power supply. Attach appropriate ESD protection at this time. |
The following items are required for installing the MAS-26 power supply:
n Two Phillips screwdrivers, No.1 and 2
n One medium flat-blade screwdriver
n One pair of medium size needle nose pliers
n Digital Multimeter (DMM) or Digital Voltmeter (DVM)
Following is the procedure for accessing the M chassis:
Step 2: Locate the three screws that secure the card cage access panel. Use the flat-blade screwdriver to turn each of these screws 1/4 to 1/2 turn counterclockwise until the screws pop up.
Step 3: Loosen the three screws at the bottom edge of the card cage cover (do not remove these screws completely). Carefully remove the cover and set it aside.
Step 4: Orient the chassis so that the rear (the side with the ports) is to your left, the front of the chassis (the side with the LED) is to your right, and the card cage opening is on the side of the chassis facing away from you. This will place the power supply on the side of the chassis closest to you. Looking straight down at the power supply, the position of the terminal strips and wires attached to them should resemble the wiring diagram in Figure 3.
Proceed to "Removing the Suspect Power Supply."
Following is the procedure for removing the suspect power supply from the M chassis:
Step 2: Use the medium flat-blade screwdriver to loosen (but not remove) the screws on the long terminal strip to which wires are attached. Pull the wires from beneath the screws.
Note: The wires from the two terminal strips may need to be routed across the top of the power supply depending upon the length of the wires in your chassis.
Step 3: Locate and remove the small angled plate covering the short terminal strip. This plate is attached with a No. 2 Phillips screw.
Step 4: Use the medium flat-blade screwdriver to loosen (but not remove) all three screws on the short terminal strip. Pull the wires from beneath the screws.
Step 5: Locate the Phillips screws (one in each corner) securing the mounting plate to the chassis base (see Figure 3).
Step 6: Remove the screws from the power supply mounting plate.
Step 7: Lift the suspect power supply (and plate) out of the chassis and set it aside.
Proceed to "Verifying the Correct AC Input Voltage of the New Power Supply."
The U.K. power supply in your M chassis must operate at 240VAC. Before installing the new power supply, verify the voltage configuration. The power supply shipped to you should have an orange sticker (attached to its case or to the box in which it was shipped) that will say 240VAC.
If this sticker is not present on the power supply or shipping box, locate the Input Voltage Link jumper on the power supply. This jumper is adjacent to the short terminal strip beneath the small angled plate. Look straight down at the jumper (see Figure 3) and verify that it is set for 230VAC.
Note: Although the jumper indicates 230VAC, the nominal AC input rating of 240VAC is used throughout this document.
 | Warning The AC input voltage rating of the power supply must be equal to the AC source voltage supplied at the site. If the AC source voltage is too high, the MAS-26 will be permanently damaged. If the AC source voltage is too low, the MAS-26 will not operate correctly (if at all). A 240VAC source should only be connected to a MAS-26 power supply rated at 240VAC. |
Following is the procedure for installing the new power supply in the M chassis:
Step 2: Place the power supply in the chassis so that the side with the terminal strips is toward you. Refer to Figure 3 for correct positioning.
Step 3: Use the No. 2 Phillips screwdriver to install the screws that secure the power supply mounting plate (attached to the MAS-26) to the chassis base.
Step 4: Remove the small angled plate that covers the short terminal strip.
Step 5: Locate the AC input cable (three wires: blue, green (with yellow stripes), and brown wires wrapped in a black insulator).
Step 6: Attach the individual AC input wires to the short terminal strip using the correct orientation and color coding for each (see Figure 3).
Step 7: Replace the small angled plate that covers the short terminal strip.
Note: After the AC input cables are in place, examine the relative lengths of the four red wires that will attach to the long terminal strip; there are two short red wires and two that are longer. The two longer red wires will attach to the first +V1 terminal position (the leftmost position on the terminal strip), and the two shorter red wires will attach to the second +V1 (the second position from the left on the terminal strip).
Step 8: Refer to Figure 3 and attach all of the wires to the long terminal strip starting with terminal position +V1 (the leftmost position on the terminal strip); use the correct orientation and color coding for each wire. Terminal positions +V4 and -V4 have no connection (NC).
Step 9: Attach the long green wire (with yellow stripes) from chassis ground to terminal position +V5.
Step 10: Carefully check all power supply wiring at this time (see Figure 3). Make certain all color coding and wire positions are correct before continuing with these procedures.
 | Caution Only after all the wiring has been correctly verified should you proceed with the following section. There should be no loose wires or parts on or near the power supply. |
Proceed to "Testing the New Power Supply."
In normal operation, the chassis will run with all cards installed; however, the power supply installation must first be checked with only one card installed to prevent possible damage to the cards. This test will require the DVM.
 | Warning Before accessing the chassis interior, turn off power to the chassis and unplug the power cord. Use extreme caution around the chassis since potentially harmful voltages are present within. Attach appropriate ESD protection at this time. |
 | Caution To avoid overheating the chassis during the following steps, apply power to the chassis only long enough to check the power supply voltages. |
Following is the procedure for testing the new power supply in the M chassis:
Step 2: Locate the edge ejectors on the cards inside the card cage. (See Figure 4.) Partially remove all cards in the card cage, except the processor card (located in the top slot in the card cage), by sliding them approximately one inch out of the backplane slots. Do not completely remove them from the card cage. The processor card will provide a load on the power supply.
Step 3: Disconnect cables only as necessary to partially remove the cards and carefully note the positions of any cables disconnected.
Note: Partially removing the cards breaks the power supply contact and protects the cards while testing for a possible bad connection.
Step 4: Plug in the chassis, power it on, and set the DVM for "DC voltage" operation.
 | Warning To avoid short circuit hazard, exercise great care with the DVM probes. Do not touch more than one wire with one probe. A short circuit could cause damage to all cards and the power supply. |
Step 5: Refer to Figure 5 and locate position 1 at the far left of the backplane (black wire, 0V) Touch this point with the black (negative or ground) probe of the DVM and maintain contact through the following step.
Step 6: Touch the red probe to each wire position on the back plane (positions 2 through 9) and compare the voltage measurements with those listed in
Table 1. If a measured value falls outside the voltage range given, confirm your wiring connections and recheck your voltages.
Table 1 Voltage Ranges for Backplane Test Points (TP)
If all measured voltage values are within the specified ranges, this completes Configuring and Installing the U.K. Power Supply in the M Chassis."
Turn of the power, disconnect the power cable, and proceed as follows:
n Reconnect all cards to the backplane.
n Replace the top cover and the card cage cover on the side of the chassis using all removed screws (see Figure 2).
If any measured voltage values are not within the specified ranges, proceed as follows;
n Check problematic power supply connections and repeat Steps 4-6 completely.
If measured voltage values still vary from the specified ranges, immediately turn off the power to the chassis and contact your service representative for further guidance.
When the system tests successfully, turn off power to the system. Reinstall any other hardware that you may have removed or loosened during the installation procedure, replace the top panel, and then reboot the system.
The system is now ready to be installed in the network.
Posted: Thu Nov 6 16:19:33 PST 2003
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