TP LINK WR9841 weird issue

[Jethro_uk]

Woke up to discover power supply had failed.

After the usual trawl through the 100 or so wallwarts I have, obviously I was never going to have the 9V one I needed, so I resorted to using my universal one.

All good, powered router back up, immediately got connected to internet. All well.

For a few minutes. Then my laptop squealed about a disconnected cable, and SWMBO noted she'd lost the wireless.

For a few seconds.

Then back again.

And off.

And on.

Have tried leaving power off for 30 minutes and a hard reset and reloading config. All to no avail.

Can get a replacement for £15 so, annoyed, but not the end of the world.

But it's an odd failure mode ? Noting in the (rather basic) log file on the router. And when the outages happen, the lights continue flicking merrily showing traffic and wireless - they don't all go on and off as if the router is resetting itself (which the uptime stats also confirm).

[Andy Burns]

is the generic PSU beefy enough for the router, or maybe it's been in the junk drawer for so long its caps have dried out?

[Jethro_uk]

Ah, re-reading the status page it *is* resetting every <x> minutes.

Grrr

[The Natural Philosopher]

internal power supply is prolly dodgy and that's what took out wallwart, Think ethernet runs on different voltages to the CPU etc.

[Jethro_uk]

Just to update - more careful reading shows the router *is* resetting every few minutes looking at the stats.

Getting the magnifier out, the original PSU was 0.6A@9V, and the universal on I dug out was only 300mA (despite being heavy enough to fell an ox ?).

Digging into my setup I found another universal supply that's rated at 1A for 9V. With which the router appears to be back to stability.

If you don't hear from me again in this thread it's fixed :)

Many thanks all.

[Theo]

The old one is likely transformer based and maybe it has a thermal cutout in series with the transformer. You can draw more than 300mA until the transformer gets too warm and the cutout trips. Then it cools, resets, trips, etc.

Theo

[Brian Gaff (Sofa]

Now are you sure the demise of the psu was just random? It could be that something in the router is having current issues and is affecting hardware internally. Also you may be lucky if the universal one you are using is in fact switch mode not analogue. If its a linear one how smooth is the dc output, if it has a lot of 50 or 100 Hz on it due to load, then this to can be an issue. Brian

[Brian Gaff (Sofa]

Yes, another thing to note is that it may be only needing a 9v due to regulation for 5 v in the router so it may well be happy with 12v as long as its not unregulated of course. Brian

[Jethro_uk]

I'd feel happier trying that out if I had a spare :)

[Jethro_uk]

From experience, yes. Over the years I've had a few bits of kit "fail" and it's almost always the cheapest part of the setup - the manufacturer supplied cost-a-few-pennies PSU.

If I was kitting out a grown up server/network infrastructure, I'd source a reliable set of PSUs for all the kit before installation. I have no evidence that Netgear (for example) supply better the PSUs for their commercial kit.

Although that said, it's possible that being on a regular domestic AC supply is a factor ? I have surge protection, but even so, the supply can be a little buzzy ....

[The Natural Philosopher]

mains cap in switched mode psu and the rectifiers that feed it dont last forever

[Fred]

Never had one fail yet and I don?t bother to unplug the wall warts when not using them.

[John Walliker]

I've had plenty of failed wall warts. It is nearly always the output capacitor that dries out due to heating from ripple current, often combined with being next to a hot rectifier diode. Leaving them plugged in when not heavily loaded isn't a problem as there is negligible ripple current in the output capacitor when there is no load. When they fail in this way, the output ripple voltage becomes excessive and the device being powered then misbehaves, sometimes in mysterious ways.

John