IBM iSeries 270 Service Manual page 137

Table 2. Check LGA-ST for the ability to detect passing conditions
MCM
Rocker switch green
position LED
Forward ON
MCM/L3
PWR/GND
Backward OFF
L3
PWR/PWR
This ends this procedure.
Test method 1: Testing MCM and passthru modules for a short circuit
1. After ensuring that the LGA-ST is functioning properly in the procedure above, install the capacitor
book in the system, connecting the LGA-ST test box onto the capacitor book 9 pin D-shell connector.
2. Power down the system. See Power on/off the system and logical partitions.
3. Ensure the UEPO is off.
4. Disengage all DCAs from the backplane.
5. Install an MCM/passthru module.
6. Press the Rocker switch forward to the MCM/L3 PWR/GND position. This checks the MCM passthru
for power to ground shorts. It also checks the L3s for power to ground shorts with the switch in this
position.
Note the following:
v The green MCM LED must be lit for a pass condition. If the amber MCM LED is lit, there is a
short across the MCM/passthru. Perform the following:
a. Inspect the interposer for shorts.
b. Replace the MCM/passthru in the system, and repeat this step.
c. If the short remains, replace the MCM/passthru.
v The green L3 LED must be lit for a pass condition. If the amber L3 LED is lit, there may be a
short between one of the two L3 voltages and GND which is a fail state, or the combination of
memory books, I/O books, and L3 in parallel are creating a low resistance. Before powering on,
perform Test method 1: Testing L3 cache modules for a short circuit (See page 125) to ensure that
no shorts are present on the L3 modules.
7. Repeat steps 5 (See page 125) and 6 (See page 125) until all required MCMs/passthrus are installed.
This ends this procedure.
Test method 1: Testing L3 cache modules for a short circuit
1. After ensuring that the LGA-ST is functioning properly, install the Capacitor book in the system by
connecting LGA-ST test head onto the Capacitor book 9 pin D-Shell connector.
2. Power down the system. See Power on/off the system and logical partitions.
3. Ensure the UEPO is off.
4. Disengage all DCAs from the backplane.
MCM L3 L3
amber green amber
LED LED LED
OFF ON OFF
OFF ON OFF
Battery low
amber LED Note
OFF
1. If Battery Low LED is ON, or if no LEDs are
lit, replace the battery before proceeding.
2. If the MCM and L3 LEDs are not as defined
here, disengage the capacitor book from the
system. If the LED state is not as shown after
disengaging the capacitor book, the LGA-ST
is defective. Replace it before proceeding.
OFF
1. If Battery Low LED is ON, or if no LEDs are
lit, replace the battery before proceeding.
2. If the MCM and L3 LEDs are not as defined
here, disengage the capacitor book from the
system. If the LED state is not as shown after
disengaging the capacitor book, the LGA-ST
is defective. Replace it before proceeding.
Analyze hardware problems
125