The article suggests one more diligent check of power input before confirming PSM hardware issue against chassis alarms.

PSM failed alarm set in the chassis, and log messages report the same:
 

user@MX2020> show chassis alarms no-forwarding

3 alarms currently active
Alarm time              Class Description
2023-11-07 14:47:23 CST Major PSM 14 Output 5V Fail
2023-11-07 14:47:23 CST Major PSM 14 Output Failure
2023-11-07 14:47:23 CST Major PSM 14 Not OK

user@MX2020> show chassis power | no-more
......
PSM 14:
 State:    Present
 Capacity: 3400 W (maximum 3400 W)
 DC output: 0.00 W (Upper Zone, 0.00 A at 51.25 V, 0.00% of capacity)
......

user@MX2020> show log messages | match PSM
Oct 27 17:53:34 2023 MX2020 alarmd[80180]: %DAEMON-4: Alarm set: PSM color=RED, class=CHASSIS,reason=PSM 14 Not OK
Oct 27 17:53:34 2023 MX2020 craftd[23510]: %DAEMON-4: Major alarm set, PSM 14 Not OK
Oct 27 17:53:34 2023 MX2020 chassisd[23505]: %DAEMON-4-CHASSISD_PEM_VOLTAGE: Power supply 14 reports problem; check output voltage
Oct 27 17:53:34 2023 MX2020 alarmd[80180]: %DAEMON-4: Alarm set: PSM color=RED, class=CHASSIS, reason=PSM 14 INP1 Failure
Oct 27 17:53:34 2023 MX2020 craftd[23510]: %DAEMON-4: Major alarm set, PSM 14 INP1 Failure
Oct 27 17:53:34 2023 MX2020 chassisd[23505]: %DAEMON-4-CHASSISD_PEM_INPUT_BAD: Input 1 failure for power supply 14 (status bits: 0x0); check circuit breaker

user@MX2020> test chassis psm slot 14 read status |no-more | match INP
INP0 voltage out-of-range : 0
INP DC(1) or AC(0) : 0
INP1 present : 1
INP0 present : 1
Active INP at the time : 0
INP1 voltage out-of-range : 0
INP1 voltage Too-High : 0
INP1 voltage Too-Low : 0
INP1 voltage Too-Too-Low : 0
INP0 voltage Too-High : 0
INP0 voltage Too-Low : 0
INP0 voltage Too-Too-Low : 0

Root Cause

• The alarm can occur due to loose or faulty power input connection to the PSM.

• If the input voltage reading is normal (0) but the alarm persists, the PSM itself may be faulty (hardware issue).

Solution

• Run the command below to verify input status:

   

  test chassis psm slot <slot-number> read status | no-more | match INP

• Check the field “INP voltage out-of-range”.

  • If the value is 1, it indicates a real input power problem.
    → Ask customer to verify power input source (cables, connectors, and power feed stability).

  • If the value is 0 but the PSM alarm still persists, this usually points to a hardware fault.
    → Proceed with PSM replacement and RMA.