Green Power On Led Does Not Illuminate - Keysight N8973B Service Manual

Boot Up and Initialization Troubleshooting
Potential Problems During Boot Process

Green Power On LED Does Not Illuminate

Control of the green front panel Power On LED comes from the A4 CPU 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
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
2. Remove the AC power cord and then remove the instrument cover. Refer
3. Remove the MP7 Top Brace. Refer to
4. With AC power connected to the rear of the instrument but without
Does the voltage at R867 measure 5 VDC?
If yes:
If no:
Before replacing the power supply, verify the midplane and motherboard
interconnects are mechanically secure.
54
"Yellow Standby LED Does Not Illuminate"
an 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.
to Chapter 15, "Assembly Replacement Procedures", on page 389
manual.
Procedures", on page 389
turning it on, leaving it in standby mode, measure the voltage at the top
side of R867 of the A7 Midplane board assembly. See
location.
Proceed to step 5.
Replace the A6 Power Supply assembly.
section before proceeding.
Chapter 15, "Assembly Replacement
in this manual.
Keysight NFA Series Noise Figure Analyzers Service Guide
in this
Figure 2-4 for R867