Asus RT-AX86U no start - seek troubleshooting help

[e_identity]

I would appreciate any ideas for fixing my Asus RT-AX86U router running Merlin Firmware. It stopped working yesterday and will no longer power up. It is almost four years old and out of warranty. It was working fine until it stopped. There is no visible damage. I did not notice any electrical problems at the time. Now, the router will not start at all. When I plug it in, no LEDs are illuminated and I cannot access it remotely on my local network. I like this router a lot, and would like to fix it. I would appreciate any help. More details below:

I searched this forum and went through the trouble shooting steps on the Asus website at: https://www.asus.com/support/faq/1050634/ No change.

There is a power switch on the back of the router, and I tried it with the switch in both positions without any difference.

At the time it stopped working, the router was attached to a surge protector. Other items on the same surge protector (TV, Roku, Blu-Ray player) still work. No visible damage to surge protector.

Plugging it into a different electrical outlet does not help.

The power supply has no visible damage and is rated at 19.5 volts and 2.31 amps., After this problem occurred, I measured 19.5 volts DC on the original power supply. I also swapped in an alternate power supply (rated 19.5 volts and 1.5 amps) with no change.

I can no longer access the router remotely on my local network.

The reset button has no effect.

Pressing the “LED” and “WPS” buttons has no effect.

I temporarily replaced the Asus router with an old router I had lying around. With the replacement, my internet connection appears to be working fine.

I am in the U.S. I purchased the Asus router from Best Buy in August 2021, and the 2 year warranty is now expired.

Thanks for any help you can offer.

e

 

[L&LD]

Welcome to the forums @e-identity.

Try another power supply of equal Voltage and equal or higher Amperage. The test you did with the weaker 1.5A power supply isn't a valid one.

Unless you or someone you know can take apart the router and assess the circuits, cheaply, you're better off looking for a new router right now.

 

[e_identity]

L&LD,
Thanks for the response. I know the test w/ the lower amp PS didn't have the right amps, but I was what I had available and I was hoping the LEDs would flash if it was a bad PS issue. I will keep looking for a better alternative to test the PS.
I can open the case, but can't assess the circuits.
I understand it may be time for a new router.
Thanks for your advice!
e

 

[ColinTaylor]

I have the same router as you and the maximum power draw without any USB devices plugged in is ~9 Watts. So your 29 Watt (19.5 volts x 1.5 amps) test power supply is way more than is needed. So that's not the problem. Even if your power supply was marginal (which it isn't) it would be sufficient to flash the LEDs momentarily even if it couldn't fully boot up.

To be honest it sounds like the VRM has blown inside the router. So you need somebody to repair it that knows what they're doing. The only other thing I can think of is that the power socket may be broken or not fully connected to the PCB. But that seems unlikely unless there was some recent rough handling, like pulling on the cable or being dropped.

 

[e_identity]

ColinTaylor,
Thanks for your response and the power analysis.
The power socket inside the router is not loose. There is no visible damage and the other connections on the back of the router are flush with the surface. The router had no signs of rough handling--actually looks like new.
Unfortunately, repairing the voltage regulator module is beyond my skills.
I appreciate your suggestions!
e

 

[ColinTaylor]

It might be worth taking it apart anyway and giving it a visual inspection, particularly where the power socket and on/off button are soldered onto the PCB. You could reflow those solder connections just in case there's a dry joint. If you have a multimeter you could also check the continuity of the on/off switch to make sure it's still working and hasn't failed into the "off" state (it's been known to happen with the push button type of switches).

 

[Tech9]

Your test power supply @e_identity was good enough, but no signs of live means some internal issue. Start looking for replacement.

 

[e_identity]

ColinTaylor,
Thanks again. I opened the case, and used my multimeter.
Circuit board looks new w/ no obvious signs of damage.
I verified that the PS connector (end of PS wire) had 19.95 V DC
On back of circuit board, there are three solder spots opposite the power supply connector. All combinations 0 V DC w/ PS connected--tested w/ switch in both positions.
On back of circuit board there are three soldered pins opposite the power switch. All combinations and switch positions, 0 V DC w/ PS connected. With switch on (side of rocker w/ white dot down), continuity b/t bottom and mid pins (0.1 ohms) and all other combinations open (88 k ohms). With switch off (side of rocker w/ white dot up), continuity b/t top and mid pins (0.1 ohms) and all other combinations open (17 k ohms).
I am not sure how to interpret this information.
Thanks again!

 

[e_identity]

I am working on a theory that it is an intermittently bad PS. Sometimes the plug is 19.95VDC, and sometimes 0VDC.
My power supply is an ACBel ADH011 (19.5 V x 2.31 A = 45 W) with 5.5 X 2..5 plug. I am searching for a replacement.
All my old laptop adapters have the wrong plug size.

edited for typo on amperage

 

[L&LD]

I hope your test power supply wasn't good enough then.

(And a new PS powers the router up).

 

[Ola Malmstrom]

Could it be that your surge protector is worn out and didn't really protect anything? You may have been just lucky that the other equipment survived. I have had equipment fried for no apparent reason - but there were traces of something happening on the PCB.

Did you try to re-solder the solder joints where the power enters the PCB?

 

[bbunge]

Time to go to Best Buy. They will give you a 15% discount for your old router.

I had pretty much the same thing happen to an AX86U but it was two weeks out of warranty and Asus replaced it.

 

[e_identity]

To close the loop on this, my best understanding of the reason the power supply was intermittently not working is that it was automatically shutting down due to a short in the router circuit board for my Asus RT-AX86U. I had already removed the circuit board from the case. I tested the router with two old dell laptop chargers that supply 19.5V and over 2.31A (3.34A & 4.62A). The Dell laptop chargers had the wrong size barrel plug on the end of the cable, but I used an adapter to convert them to the same 5.5 X 2.5 mm barrel plug used on my router’s original ADH011 power supply. When plugged in, the barrel plug on both Dell PSs showed 19.5 VDC. When the adapter was connected to the Dell PS, the barrel on the adapter showed 19.5 VDC. When I plugged both Dell PSs with adapters into the router with the router power switch off, I could see a spark inside the plastic housing into which the PS tip is inserted (no change power switch on). I unplugged the Dell chargers and, after a while, they began working again (19.5 VDC). When plugged into the circuit board again, same spark and 0 VDC. I was able to do the same test with the original ADH011 PS with the same result. No visible debris or damage to the plastic housing into which the PS tip is inserted. The solder joints connecting the PS plug to the PCB and the plastic housing itself look very clean. Apparently, all three PSs have some circuitry that cuts out when there is a short and eventually resets on its own.

Also, I discovered that a key reason my first test with a backup PS did not work was that I had read the specifications incorrectly—it was 12V, not 19.5V. Oops!

Sadly, I will be looking for a new router now. Thanks for everyone’s help. I really like the Asus router with Merlin firmware, but I had hoped it would be more reliable!

I really appreciate the advice everyone provided!

e

 

[L&LD]

While unfortunate, 4 years is a good run. This is definitely a 'one-off' type of failure. Particularly for this model.