General Failure Code Descriptions (Upper Two Bits Fail Indicators) - HP 400 Series Servicing Manual

Test LEDs are mounted vertically on the system unit's front upper right-hand corner.
The front panel must be opened to see all of them.
Table 4-7. General Failure Code Descriptions (Upper Two Bits Fail Indicators)
Upper 2 Bits Fail Indicator
State indications only.
Required device missing or
data acknowledge failure.
Failing device.
Special codes.
(Special case highest priority codes)
4-42 Fault Isolation
LED Code and Failure Description
A
B
C
D
LEDs indicate power-up state.
E
F
G
H
A
B
C
D
LEDs indicate device.
E
F
G
H
A
B
C
D
LEDs indicate device.
E
F
G
H
A
LEDs
B
C never
D
accessed.
E
F
G
H
LEDs CPU
failed board
to timer
acknowledge failed or
data. missing.