HP RP8420 VRM Failure Analysis and Handling

1. Fault Description A) System log: normal B) MP->VFP->0 E 0 OS heartbeat C) MP->CM->PS->c->1 HW status for Cell 1 : FAILURE DETECTED Power status : on, 3.3V Module 0, VRM #8 VOLTAGE FAULT Boot is not blocked PDH memory is shared Processor Compatibility : OK RIO cable status : connected RIO cable connection physical location : PCI Domain 1 Core cell is cell 0 Attention Led is off PDHC status Leds : ***- CPU Module Slot 0 1 2 3 Populated P P P P Local 48V Good * * * * Power Enabled * * * * Power Good * * * * (* - True, P - Processor, T - Terminator) DIMMs populated: 0 . . . 4 . . . 8 . . .12 . . . * * * * * * * * 1 1 1 1 1 1 VRM's 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 Present : * * * * * * * * * * * * * * * Enabled : * * * * * * * * * * * * * * * Pwr Good : * * * * * * * * * * * * * * Front Side Bus Freq. : 200 MHz CPU Core Freq. : 1000 MHz CPU Part Number : PA8800 System Boot Rom (SFW) firmware rev 22.002 PDH controller (PDHC) firmware rev 3.023, built WED FEB 16 14:33:12 2005 MICE revision is 1.0
2. Fault Analysis Consulting the rp8420 user manual shows that 3.3V is a high-voltage VRM, PN: 0950-4123.
3. Spare Part Replacement A cell board has 15 VRMs, which are high-voltage VRMs and low-voltage VRMs. There are three common ways to distinguish them:

• Low-voltage VRMs are marked "0.88-1.9V", high-voltage VRMs are marked "1.75-3.3V".
• Low-voltage VRM main pins are in the middle of the slot, high-voltage VRM main pins are at the edge of the slot. (To be verified)
• Low-voltage VRMs have small heatsinks, high-voltage VRMs have large heatsinks. Through the system firmware, the faulty VRM can be located; LV stands for low-voltage VRM, HV stands for high-voltage VRM.

Steps to remove a VRM:

1. Remove the right-side panel of the machine (see later for details).
2. Power off the cell board to be maintained in the MP command line (MP->CM->PE->c->).
3. Make sure the green LED on the right or left side of the cell board is off before removing the cell board.
4. Pop out each handle, slide the lock to the unlocked position. Pull the handle outward to detach the cell board from the backplane slot.
5. Slide the cell board out of the chassis.
6. Remove the memory and CPU protective covers.
7. Find the VRM to be replaced.
8. Loosen the VRM retaining screw.
9. Pull the VRM out from the cell board.

Replacing the VRM

1. Insert the new VRM into the slot.
   • Note: Make sure the pin orientation is correct before inserting the VRM.
2. Tighten the screw.
3. Put back the memory and CPU protective covers on the cell board.
4. Push the cell board into the chassis.
5. Power on and test the cell board.
6. Install the right-side panel.

Steps to remove the side panel

1. Wear an anti-static wrist strap.
2. Loosen the blue screws that secure the side panel to the chassis.
3. Slide the side panel toward the rear of the host.
4. Place the removed side panel in a safe location.