IBM Power775 Service Procedure page 11

Figure 6 UEPO Panel With BPA-A BPCH Bypass Switch in Bypass below highlights the UEPO loop path when the "2 Pole Bypass
Switch" is closed. Note that the "2 Pole Bypass Switch" being closed acts as a short across the UEPO switch. It forces the UEPO
loop to remain closed, the system to be kept running, and the UEPO Panel green LED to stay lit. This allows us to concurrently
remove the UEPO cables without opening the UEPO loop or causing a hard system power down. It is important to remember that
once the new UEPO Panel is installed, we place both BPCH "2 Pole Bypass Switches" back in the normal (or open) position to
allow the UEPO Panel control to function as intended.
Power775 UEPO Cable Service Procedure
PN: 41U8503, EC N44172
BPA-A
BPR
BPE Backplane BPCH
F M F M
M F
M F
F M F M
BPR
M F
M F
BPR
M F
M F
BPR
F M
F M
M F
M F
F M
F M
BPR
M F
M F
BPR
M F
M F
Figure 5 UEPO Normal Operation (One of 4 Loop Paths Highlighted)
BPA-A
BPR BPCH
BPE Backplane
F M F M
M F
M F
F M F M
BPR
M F
M F
BPR
M F
M F
BPR
F M
F M
M F
M F
F M
F M
BPR
M F
M F
BPR
M F
M F
Figure 6 UEPO Panel With BPA-A BPCH Bypass Switch in Bypass
BPA-B
EPO BPCH
BPE Backplane
F M
M F M F M F
F M M F
M F M F
F M M F M F M F
F M M F
M F M F
Logic
BPA-B
EPO
BPCH BPE Backplane
F M
M F M F M F
F M M F
M F M F
F M M F M F M F
F M M F
M F M F
Logic
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BPR
F M
F M
BPR
F M
F M
BPR
F M
F M
BPR
F M
F M
BPR
F M
F M
BPR
F M
F M
BPR
F M
F M
BPR
F M
F M
BPR
F M
F M
BPR
F M
F M
BPR
F M
F M
BPR
F M
F M