Green Power On Led Does Not Illuminate - Agilent Technologies N9039A Service Manual

Green Power On LED Does Not Illuminate

Control of the green front panel Power On LED comes from the A4 Processor
board assembly. This signal is routed through the A7 Midplane board and is then
buffered on the A8 Motherboard before being sent to the A1A2 Front Panel
Interface board through W1. Of course, the power for this all originates with the
A6 Power Supply Assembly. When the Power On LED does not come on it could
be due to any one of these assemblies. This procedure will help to determine which
one is the cause.
This procedure assumes that the yellow Standby LED does turn on when the AC
power is connected to the rear panel of the instrument. If it doesn't, refer to the
"Yellow Standby LED Does Not Illuminate"
If the instrument turns on and operates properly but the green Power On LED does
not work then all that will need to be done is to trace where the control signal for
the LED is being lost using the routing information in the preceding paragraph.
1. The Power On LED will only turn on when the instrument is connected to an
2. Remove the AC power cord and then remove the instrument cover. Refer to
3. Remove the MP7 Top Brace. Refer to
4. With AC power connected to the rear of the instrument but without turning it
Does the voltage at Test Point 518 measure 5 VDC?
If yes:
If not:
Before replacing the power supply, verify the midplane and motherboard
NOTE
interconnects are mechanically secure.
Chapter 2
AC source that has a voltage level and frequency of that specified for the
instrument and the front panel On/Off button has been pressed. Before
proceeding verify that these requirements are being met. Refer to the
instrument rear panel for these requirements.
Chapter 7, "Assembly Replacement Procedures," on page 161
Procedures," on page 161
on, leaving it in standby mode, measure the voltage at Test Point 518
(POWER_ON) of the A7 Midplane board assembly. See
Point 518 location.
Proceed to step 5.
Replace the A6 Power Supply assembly.
Potential Problems During Boot Process
section before proceeding.
Chapter 7, "Assembly Replacement
in this manual.
Troubleshooting
in this manual.
Figure 2-3 for Test
39