Nokia 7705 SAR power supply failed: Diagnose & Fix
By Sai Kiran Pandrala · reviewed by Sai Kiran Pandrala, Editor Last verified: 2026-05-30
| Vendor | Nokia |
|---|---|
| Operating system | SR OS / SR Linux |
| Category | Hardware Failure |
| Skill level | Intermediate to advanced |
| DIY-able? | Yes with CLI access; some scenarios need Nokia Customer Care + RMA. |
If you have ever stared at a Nokia 7705 SAR that just refused to come up, you know the muscle memory: serial console at 9600 8N1, wait for the BOF> (Boot Options File) line, hope it actually paints. On SR OS / SR Linux the first move is always `show version` and `show chassis environment`. if those return cleanly the box is alive enough to talk to you, which is the difference between a ten-minute fix and an RMA paperwork morning.
I keep a small notebook of Nokia part-numbers next to the rack because the LED legend differs between hardware generations. The SR OS / SR Linux platform tends to tell the truth in `show` output before the front-panel LED catches up, so trust the CLI first.
This guide assumes you have console access and an active Nokia Customer Care entitlement. If the device is out of warranty, skip straight to the recovery section, most of the steps still apply, you just lose the RMA option at the end.
What this guide covers
Diagnose and recover from power supply failed on a Nokia 7705 SAR.
Step-by-step
- Confirm which PSU failed.
- Verify the remaining PSU has enough capacity for the device + line cards + PoE budget.
- Note the failed PSU's part number.
- Replace during a maintenance window: most enterprise PSUs are hot-swappable.
- After replacement, confirm both PSUs show OK.
CLI / commands
# Verify hardware state
show version
show chassis
show chassis environment
# Collect for Nokia Customer Care
admin tech-support
When to RMA
- Repeated failure after re-seat and power-cycle
- Visible burn, scorching, or physical damage
- POST or memory diagnostic failure
- Hardware crashinfo without a software workaround
Frequently asked questions
Will this work on my specific SR OS / SR Linux version?
The procedure reflects current SR OS / SR Linux behaviour. Older releases may need minor syntax adjustments, use the CLI help (? or tab-completion) to verify.
Should I open a Nokia Customer Care case immediately?
Open one if you suspect hardware failure or the symptom persists after a maintenance-window reload. Make sure your support entitlement is active first.
Where can I find the Nokia official documentation?
https://documentation.nokia.com. search the product family + feature name.
Is this procedure safe in production?
Test in a lab or maintenance window first. Capture pre-change state so you can roll back.
Related guides
Related fixes
Related guides worth a look while you sort this one out:
- Nokia 7250 IXR-R6 power supply failed: Diagnose & Fix
- Nokia 7250 IXR-S power supply failed: Diagnose & Fix
- Nokia 7250 IXR-X power supply failed: Diagnose & Fix
- Nokia 7705 SAR fan tray failed: Diagnose & Fix
- Nokia 7705 SAR: How to rollback to the previous image after a failed upgrade
- Nokia 7705 SAR all ports dead: Diagnose & Fix
References
- Nokia support portal: https://customer.nokia.com
- Nokia knowledge base: https://documentation.nokia.com
- Nokia security advisories: https://www.nokia.com/about-us/security/vulnerability-management/
- Open a case: https://customer.nokia.com
Reference material, not professional advice. Validate against your specific SR OS / SR Linux version and test in a non-production environment before applying.
Common patterns we see
When this symptom shows up on a Nokia device, three patterns repeat:
1. Recent firmware update changed behavior, the symptom started within a week of an OTA push. Rollback or wait for the hotfix. 2. Environmental trigger: temperature, humidity, line voltage, network changes. Look at what changed in the environment. 3. Cumulative wear, components like batteries, gaskets, fans degrade over time. Replace the consumable rather than chasing a software fix.
Knowing which pattern applies saves time on the wrong fix.
Safety + preconditions
Before any work on a Nokia device:
- Unplug from mains for any internal-access procedure.
- Discharge stored energy (capacitors in PSUs, residual battery charge) per manufacturer guidance.
- Use ESD-safe handling for boards and modules. no carpet, no wool sleeves.
- Avoid moisture; never apply liquids near vents or connectors.
- If you smell smoke, see scorch marks, or feel uneven heat, stop and escalate.
Quick verification
Before you walk away from a Nokia device fix, run through:
1. Reproduce the original trigger, does the issue reappear? 2. Check the device's status / health screen for any new alerts. 3. Confirm paired devices (app, hub, controller) reconnected. 4. Save / commit any configuration changes per the device's normal workflow. 5. Note the change in your maintenance log with date + firmware version.
When to call Nokia support instead
Escalate if:
- The same symptom returns within 24 hours of a clean fix.
- You see physical damage (burn marks, swollen battery, cracked PCB).
- The device is in warranty and a hardware replacement is the cheaper outcome.
- Repair requires specialised tools you don't own (alignment jigs, calibration software).
- Following the official path keeps the warranty intact, which matters more than the time spent.
More frequently asked questions
Does this affect other devices on my network?
Generally no. The procedure is local to this device. Network-side changes (firmware updates that affect TLS, SMB, or routing) are flagged explicitly in the steps.
What if the fix returns after a reboot?
Persistent fault returns mean either: a hardware fault (escalate), a configuration that's being overwritten by a sync source (check cloud profiles), or a regression in a recent firmware update (rollback).
How long does this fix usually take?
Most users complete the steps in 20-45 minutes the first time, and 5-10 minutes on subsequent runs once the menu paths are familiar.
Will this void my warranty?
Applying official firmware updates and following the user manual will not affect warranty. Opening sealed components, jumping safety circuits, or using third-party parts can void warranty in most jurisdictions.
Is it safe to apply during business hours?
If the device is in production use, apply during a scheduled maintenance window. Most procedures need 2-15 minutes of downtime. Capture pre-change state so you can roll back if needed.