|
|
Product Numbers: MAS-28M= and MAS-28C=
The primary replacement part for this procedure is the MAS-28 175 watt power supply, and is recommended for use in M and C chassis currently equipped with a MAS-21 power supply. You must determine the power supply you have and use the appropriate documentation for that power supply.
 | Caution This procedure is recommended only for experienced technicians and engineers because access to the chassis interior is required. 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, contact a service representative. |
 | 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. |
The MAS-28 will operate with either 110 volt or 220 volt alternating current (AC) source input (auto-ranging) and provides direct current (DC) output voltages of ± 5 volts and ± 12 volts.
This document is part of a kit which includes all the parts and hardware necessary to replace the MAS-21 power supply with the MAS-28 power supply. This kit is referred to as the MAS-28M= for the M chassis and the MAS-28C= for the C chassis. These two kits differ only by the chassis backplane, which has two slots for the C chassis and four slots for the M chassis. Make certain you have the kit that applies to your chassis-type. Each kit includes the MAS-28 power supply and mounting plate, the appropriate chassis backplane, a new switch assembly, and assorted wiring and hardware.
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, a defective card 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 1 to 10 Mohms.
Refer to the following procedures and accompanying illustrations to access and remove the MAS-21 power supply and to install the new MAS-28 power supply. Before you start the installation procedure, read through this entire document to familiarize yourself with the required tasks.
 | Warning Before accessing the chassis interior and removing any cards, turn off power to the chassis and unplug the power cord. High voltages may exist in or near the power supply. Use extreme caution when working with the power supply. Attach appropriate ESD protection before beginning this procedure. |
Once you have taken the necessary ESD precautions, you can proceed with this upgrade procedure.
The following tools and parts are required for this procedure:
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)
n The MAS-28C upgrade kit for the C chassis or the MAS-28M kit for the M chassis
Each kit should include the following:
Note: The following two procedures differ for M and C chassis. Select the appropriate section depending upon your chassis type.
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 back (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 4.
Proceed to "Removing the MAS-21 Power Supply and Components."
Following is the procedure for accessing the C chassis:
Step 2: Orient the chassis so that the back (the side with the ports) is on your left and the front (which has the LED) of the chassis is on your right. This will place the power supply on the side of the chassis closest to you after you remove the cover.
Step 3: Pull the front of the cover to the right while securing the back of the chassis with your left hand. Pull slowly and carefully; the fit is snug.
 | Caution Several cables are located close to the interior of the C chassis cover. Avoid damage to these cables by ensuring that they do not impede the cover as you remove it. |
Step 4: Pull the cover to the right until the power supply and the card cage are completely exposed, but do not pull the cover completely off.
Step 5: Looking straight down at the power supply, the position of the terminal strips should resemble the wiring diagram in Figure 4.
Proceed to the section, "Removing the MAS-21 Power Supply and Components."
The terminal strips on the MAS-21 power supply use modular connections to the chassis backplane. Because the MAS-28 power supply and switch assembly use individual wires, the chassis backplane and switch assembly (used with the MAS-21) must be replaced with a new components that are capable of connecting to the MAS-28.
Following is the procedure for removing the MAS-21 power supply:
Step 2: Disconnect the two white modular connectors attached to the terminal strips on the MAS-21 power supply. These connectors are located at each end of the power supply.
Step 3: Disconnect the modular connector between the backplane and the LED on the chassis front.
Step 4: Disconnect the modular connector attached between the backplane and the fan. It may be necessary to cut the nylon cable ties (holding the fan/backplane wires) with a small wire cutter, if so, do not cut the fan wires. These wires may be wedged between the fan baffle and the rear of the card cage, so take care when disconnecting these wires.
Note: There are two connectors and two fans in the M chassis and one connector and one fan in the C chassis.
Step 5: Locate and remove the six No. 2 Phillips screws (located around the outside edges of the power supply) that secure the MAS-21 power supply to the chassis base. Use the needle nose pliers to remove any inaccessible power supply screws from inside the chassis.
Step 6: Lift the MAS-21 power supply (and all loose screws) out of the chassis and set it aside. Proceed to the section, "Removing the Old Chassis Backplane."
Following is the procedure for removing the chassis backplane:
Step 2: Disconnect and remove all the cards in the card cage. Note the position of each card in the card cage and the position of the attached cables.
Step 3: Look straight into the front of the card cage and locate the small Phillips screw toward the top of the left mounting bracket holding the left end of the backplane. Use the No. 1 Phillips screwdriver to loosen, but not remove, this screw.
Step 4: Carefully lift the backplane out of its vertical mounting bracket and set it aside.
Note: It also may be necessary to loosen (but not remove) the white nylon alignment screw (using the small flat-blade screwdriver) located on the outside edge of the right backplane mounting bracket, if so, note the number of turns of the screw required to loosen the backplane.
Proceed to the section, "Removing the Old Switch Assembly."
Following is the procedure for removing the switch assembly and wiring:
Step 2: Locate the 5/16'' nut securing the three green and yellow ground wires that attach to the modular connectors of the power supply, the chassis base, and the switch assembly (see Figure 4).
Note: There should be three green and yellow chassis ground wires: one between the switch assembly and the chassis base, a second from the chassis base to the short modular connector, and a third from the chassis base to the long modular connector.
Step 3: Use the 5/16'' nut driver to remove the nuts and wires from the chassis ground bolt attached to the chassis base; set the nuts and washers aside.
Step 4: Locate and remove the two No. 1 Phillips screws that secure the switch assembly to the chassis rear panel(see Figure 4), and set these screws aside.
Step 5: Carefully pull the switch assembly (and all attached wiring) through the hole in the chassis rear panel, and set this assembly aside.
Proceed to the section, "Installing the MAS-28 Power Supply and Components."
Following are the procedures for installing the new switch assembly, chassis backplane, and MAS-28 power supply in the M or C chassis (differences between chassis types are noted as necessary):
Following is the procedure for installing the new switch assembly. For comparison, the old single-pole single-throw (SPST) switch assembly is shown next to the new double-pole double-throw (DPDT) switch in Figure 5. If the DPDT switch you received does not appear as in Figure 5, contact your service representative for information on how to proceed.
Step 2: Use the two No. 1 Phillips screws removed from the old switch to attach the new switch assembly to the chassis rear panel. Do not overtighten these screws.
Step 3: Place the round lug at the end of the short green and yellow wire (attached to the bottom of switch assembly) over the chassis ground bolt on the chassis base (see Figure 6) and install a washer and nut (use the 5/16'' nut driver).
Step 4: Place the round lug at the end of the short green and yellow wire (bundled with the brown and blue wires) over the ground bolt. Do not install a washer and nut.
Step 5: Place the round lug on the long (approximately 15'') green and yellow wire (included with the kit) over the ground bolt and install a washer and nut. The other end of this ground wire will be attached to the long terminal strip on the MAS-28 in a later step.
Proceed to "Installing the New Chassis Backplane."
Following is the procedure for installing the new chassis backplane:
Step 2: Position the backplane over the chassis so that the card slots are toward you, and the backplane wires are at the top of the backplane.
Step 3: Align the left and right edges of the backplane over the vertical mounting bracket slots and carefully insert the backplane into these slots; the bottom of the backplane should be resting on the bottom of the mounting bracket slots.
Step 4: Locate and tighten the small Phillips screw that holds the backplane in place; do not overtighten this screw.
Step 5: The white nylon alignment screw (located on the outside edge of the right backplane mounting bracket) should be adjusted to eliminate any movement in the backplane (use the same number of turns needed to loosen it).
Step 6: Locate the LED connector attached to the backplane (red wire and blue wire) and connect it to the LED at this time.
Step 7: Locate the fan connector attached to the backplane (yellow wire and black wire) and the fan connector attached to the fan (red wire and blue wire).
Note: The backplane wires (that connect to the fan) are yellow and black, while the wires on the fan are red and blue.
Step 8: Orient the connectors so that the yellow wire (from the backplane) aligns with the red wire (from the fan) and connect them at this time.
Proceed to the section, "Installing the MAS-28 Power Supply."
The MAS-28 has a different physical design and layout (than the MAS-21) and is shipped with a mounting plate attached to accommodate the M or C chassis.
Following is the procedure for installing the MAS-28 power supply:
Step 2: Remove the new power supply (with the attached mounting plate) from its packaging.
Step 3: Loosen all of the screws on terminal strips TB1 and TB2 (to which wires will be attached).
Step 4: Place the new power supply in the chassis. Refer to Figure 6 for correct positioning.
Step 5: Use the No. 2 Phillips screwdriver to reinstall the screws that secure the power supply mounting plate (attached to the MAS-28) to the chassis base.
Note: In the C chassis, five screws are used to secure the mounting plate. In the M chassis, four screws are used (the lower right screw hole in Figure 6 is not used in the M chassis).
Step 6: Locate all of the red wires and black wires from the backplane; there are four of each color. Two of each of these colors are shorter than the other two.
Step 7: Group the two short red wires together and then group the two long red wires.
Step 8: Group only the two short black wires together.
Note: These three wire pairs will be attached to specific terminal positions in the following steps.
Step 9: Starting with terminal position TB2-1, attach the wires to TB2 (follow the wiring diagram in Figure 6). Make certain to attach the wire-pairs to TB2-7 through TB2-9 (see Table 1).
Step 10: Attach the long chassis-ground wire (green with yellow stripes), coming from the chassis ground bolt, to TB2-5 (see Figure 6).
Table 1 Connections to Terminal TB2
Step 11: When all wires are secure, double check the color-coding in Figure 6 and Table 1.
Step 12: Follow the wiring diagram in Figure 6 to attach and secure the three wires (brown, blue and green with yellow stripes) to TB1 starting with TB1-1 (Line, brown wire). These wires come from the switch assembly and are shown in Figure 4 and Figure 6.
Step 13: When all three wires are secure, double check the color-coding in Figure 6.
 | Caution Do not install any printed circuit cards or power on the system until all power supply wiring is carefully verified. |
Proceed to the section, "Testing the MAS-28 Power Supply."
After you install the new MAS-28 power supply in your chassis, you can test the installation by measuring the voltages on the new power supply. Testing first will be done with all cards removed from the chassis, and then with one card installed in the chassis.
Following is the procedure for testing the MAS-28 power supply:
 | Caution To avoid overheating the chassis during the following steps, apply power to the chassis only long enough to check the fan and LED operation. |
Step 2: Observe that the chassis fan(s) is (are) operating, which will indicate that the + 12 volt power supply is operational. Also check that the LED on the front panel of the chassis is on, indicating that the +5 volt power supply is operational.
Note: If the front-panel LED flickers, this is a typical condition with no load applied and does not indicate a failure in the power supply.
Step 3: Turn off power to the chassis and unplug the power cord.
Step 4: Re-insert only the processor card (in the top chassis slot) making certain it is properly seated. It is not necessary to attach the console cable. This card will provide a load to the power supply.
 | Caution To avoid overheating the chassis during the following steps, apply power to the chassis only long enough to check the power supply voltages. |
Step 5: Plug in the power cord and turn on power to the chassis.
 | Warning To avoid a short circuit and electrical shock 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 6: Referring to Figure 7, locate position 1 at the far left of the backplane (black wire). Touch this ground reference point with the black probe of the DVM and maintain contact through the following step.
Step 7: Touch the red probe to each wire position (positions 2 through 9), exercising extreme caution, and compare the voltage measurements with those listed in Table 2. If the measured values fall outside the range given in Table 2, confirm your wiring connections and recheck your voltages.
Table 2 Voltage Ranges for Backplane Test Points (TP)
If all measured voltage values are within the specified ranges, turn of the power, disconnect the power cable, and proceed as follows:
n M chassis only—Re-insert all remaining cards and re-attach all cables. Replace the top cover and the card cage cover on the side of the chassis using all removed screws (see Figure 2).
n C chassis only—Re-insert the remaining card and re-attach all cables.Reattach the card clamps at either end of the card cage, and replace the top chassis cover using all removed screws (see Figure 3).
The system is now ready to be installed in the network.
If any measured voltage values are not within the specified ranges, check problematic power supply connections and repeat the tests.
If, after repeating the tests, any measured voltage values are outside the specified ranges, immediately turn off power to the chassis and contact your service representative for further guidance.
Posted: Thu Nov 6 16:18:37 PST 2003
All contents are Copyright © 1992--2003 Cisco Systems, Inc. All rights reserved.
Important Notices and Privacy Statement.
