AC86U sometimes powers completely off during reboot

[Val D.]

What exact power supply are you testing?

It's from an old ACER laptop, HIPRO something. I just found it in my spare parts box. Had to change the plug only to match the ASUS router. It's actually rated 19V 3.43A, 65W. In theory it can hold double the load compared to original power supply.

 

[madfusker]

Interesting.... Waiting patently over the next few weeks to see what you find.

 

[Val D.]

Interesting.... Waiting patently over the next few weeks to see what you find.

Well, in theory 19V 1.75A should be more than enough to power RT-AC86U. The router power consumption during normal operation is about 11W. Not sure what power consumption it has during the boot process though. One way to find out is to power the router off a lab power supply with current and voltage memory. It will show if the current spikes go close to 1.75A. I don't have a lab power supply at home though. I'll use the 65W power supply from now on and see if the issue continues. Again, I don't reboot very often and i don't use the reboot scheduler.

 

[ASadani]

what a pain in the a#$ the RT-AC86U is - more issues with it on this forum than its worth. Im so glad I have the RT-AC5300. Would never upgrade to the RT-AC86U - ever.

5300 is limited to about 85 Mbps on VPN whereas the 86u can take you up to 220 Mbps.

 

[Val D.]

5300 is limited to about 85 Mbps on VPN whereas the 86u can take you up to 220 Mbps.

Yes, and this spider from another planet RT-AC5300 is much more expensive and takes a lot more space than RT-AC86U for absolutely no other than marketing reasons. Bigger is not always better. Dual 5GHz band is easily achievable for free using the ISP provided router (Main Router) and another ASUS router (VPN Router). ISP router transmits 1 x 5GHz, VPN router transmits 1 x 2.4GHz + 1 x 5GHz on a different channel. Very common setup.

 

[Grisu]

This no boot after reboot issue may be power supply related. The standard RT-AC86U power supply is rated 19V 1.75A and I start to believe in some cases it may not provide enough power during the boot process. I'm testing now with a different power supply rated 19V 4A.

After 15 reboots in a row the router starts every time with no issues.
Interesting find, but the issue is very intermittent and I still can't be sure this is the solution.

Maybe thats the reason, but I dont believe that it is.
The power adapters are multi-voltage 110-240V, so in US you should have this problem much more likely than rest of world with 230V where caps will be loaded much faster du to higher voltage with half current.
Personally I truly never thought about that to be a possible issue.

Your tests will be very interesting for all of us!

 

[Val D.]

The power block is a switching power supply, no big capacitors inside. Also, a software reboot doesn't cycle the power supply, so no change in capacitors charge. My suspicions are at some point during the boot process the power supply is "on the edge" and sometimes the router fails to boot. I need some time and equipment to prove the theory though. So far the router runs perfectly fine with the 65W power supply and I did about 25 reboots already with no issues whatsoever. Good thing is I have a backup router to hold the network during my experiments.

 

[Grisu]

On output of switching power supply there are always Elkos to stabilize voltage, those I meant.
And a reboot could bring them down some ms below secure supply voltage caused by somehow more needed current which let it hang.
But still should be much more often seen in US but this phenomen is seen worldwide by some an not by others - strange world.

We should ask somone who has an already once opended RT-AC86U with this symptom to place a 1000µF/35V Elko on PCB near 19V power plug.
Could be a usable solution to the problem if it works or we will know its something else.

 

[shark]

The power block is a switching power supply, no big capacitors inside. Also, a software reboot doesn't cycle the power supply, so no change in capacitors charge. My suspicions are at some point during the boot process the power supply is "on the edge" and sometimes the router fails to boot. I need some time and equipment to prove the theory though. So far the router runs perfectly fine with the 65W power supply and I did about 25 reboots already with no issues whatsoever. Good thing is I have a backup router to hold the network during my experiments.

You will need to test a lot, since this problem is so freaking random! I have this problem as well and there was a time that i had to do lot of reboots here to setup somethings and the problem did not appear at all, but one another time it happened on the first reboot...

Another issue that i have and that might be related, is that if i disable and enable again the Ethernet adapter on my pc(the only device connect using a cable on to the router) sometimes my router reboots

I am from Brazil and here its 110v! Now that 384.12 stable got released i am going to try a nuclear reset of the router to see if it changes anything related to the two issues that i have.

 

[Salles]

Might as well add that my RT-AC86U suffers from the same issue. However it has been a while since it occured now.

I have read opinions in this thread that the reboot scheduler is not really necessary to use. I thought a router worked best if it was rebooted once in a while. I did use the reboot scheduler before, but now I am not sure if it works anymore.
At the moment I am on firmware 384.11_2. The reboot scheduler is set on Mondays 4 am. When I looked at the uptime under Tools this morning and the week before it had not reset. Is the uptime not suppose to reset?

 

[guho]

I have the reboot problem with my ac86u. I did a remote reboot recently and had to wait for someone to get home to power cycle this router.

Could I use my ac3200's AC adapter on the Ac86u? Has DC Output : 19 V with max. 2.37 A current, which is greated than ac86u's 19 V with max. 1.75 A current. My ac3200 is unused at the moment.

 

[Val D.]

On output of switching power supply there are always Elkos to stabilize voltage, those I meant.

Yes, but on the output circuit 19V only. Input circuit 110V or 240V doesn't matter. So far I did 40 soft reboots in total and the router still boots with no issues every single time. Could it be that simple? The power supply? Some of us may have slightly "worse" power supply, still in manufacturing specs tolerances causing the issue. Very interesting if ASUS never investigated this possibility.

 

[Val D.]

Could I use my ac3200's AC adapter on the Ac86u? Has DC Output : 19 V with max. 2.37 A current, which is greated than ac86u's 19 V with max. 1.75 A current. My ac3200 is unused at the moment.

If the power plug is the same - yes.

 

[Grisu]

AFAIK they all use the same plug, polarity and voltage, only ampere differs, you can allway use an adapter with more current, less will be a problem if everything is connected or on (USB, LAN, WLAN).

 

[Val D.]

AFAIK they all use the same plug, polarity and voltage, only ampere differs

Probably. More interesting fact for me is that RT-AC3200 uses about 14W and comes with 2.37A power supply, but RT-AC86U with its 11W comes with 1.75A power supply. Really? I'm going go test some reboots with the stock ASUS power supply and 2 x USB drives in USB ports, one of them portable mechanical HDD. Let's see if I can trigger the issue by further increasing the load during the boot process.

 

[miroco]

If it's the power supply, why would a start be different to a restart? The power surge can't really be different. If the power supply is poorly filtered and you happen to have a brownout or some other kind of disturbance on the power grid at boot. A start should really be more disadvantages to a restart, since the capacitors of the ac86u at start are flat. Does anyone have the ac86u connected to a UPS?

 

[Asad Ali]

Does anyone have the ac86u connected to a UPS?

Me and I’ve seen that issue to many random times now. I don’t think it’s something power supply related, we just need to figure out a way to reproduce it accurately and making a fix won’t be an issue afterwards.

 

[Val D.]

If it's the power supply, why would a start be different to a restart?

It is not, but the problem is so intermittent we can't really do any statistics. Most of the time routers get software rebooted and this is when we see the issue. My RT-AC86U is connected to APC Back-UPS 550.

 

[CaptainSTX]

I personally don't think the power supply is the issue.

My AC86 was having the problem of not being able to either reboot from the GUI or when I held the WPS button and then connected the power cord the router would partially reset but would not reboot. I was having some other strange issues with the router so I did an RMA with ASUS.

ASUS sent me a new router and after getting it setup I had an issue with Skynet (cron failed, Ipsets failed, IPtables failed ) the replacement router got to be in the same state. I tried both the new power supply and the old power supply and the results were the same in that the router would not reboot or would shut down during the reboot.

After resetting the router, putting it into recovery mode, factory resetting, NVRAM erase, etc I got it working again so it reboots and does not power off during a reboot.

 

[miroco]

In a scenario where you have an old refrigerator with a mechanical thermostat kicking in now and then and the house is powered via overhead lines, then sensitive electronics will suffer.