Dump nand content on working ac86u

[Anonymous34]

Check the heatsink placement and the thermal pad underneath. If they look good, turn the router off until fully fixed. You are going to fry it.

Fixed the issue partially, ran the jumper wires for Power Good Indication and Analog Voltage In. Now the temperature is hovering around 80 degrees Celsius instead of 120. Voltage measured at the inductor also fell to 1.46V instead of 1.65V which may be the reason that the CPU had such a high temperature. But I may be downgrading the firmware since I read that it could help with temps.

Anyhow, thank you so much for your help and knowledge thus far. I learned more about microsoldering, and it told me that I need a microscope before I go blind.

Temps still on the high side with ambient temperature around 28 celsius

 

[Tech9]

Temps still on the high side with ambient temperature around 28 celsius

Because the VRM failure is not the only AC86U issue. The pink original thermal transfer pad leaks over time and thermal conductivity properties worsen. The gap between the CPU die and the heatsink is about 2.3mm. Copper shim with thermal paste on both sides will drop the temperatures 20C. Active cooling another 20C. This is a screenshot from my AC86U with shimmed CPU and 12V 120mm fan working on 9V behind the router, on the table:

 

[Anonymous34]

Because the VRM failure is not the only AC86U issue. The pink original thermal transfer pad leaks over time and thermal conductivity properties worsen. The gap between the CPU die and the heatsink is about 2.3mm. Copper shim with thermal paste on both sides will drop the temperatures 20C. Active cooling another 20C. This is a screenshot from my AC86U with shimmed CPU and 12V 120mm fan working on 9V behind the router, on the table:

View attachment 40261

What thickness should I get the cooper shim in? I am afraid that it would crack the die with a shim too thick. Currently having a fan blowing over the heatsink but I still think my sensor is somewhat faulty since the temperature doesn't increase significantly (beyond 2-3 celsius) without a fan. Hopefully I didn't kill the CPU at 120 Celsius if the sensor was reading it correctly.

 

[RAJ]

Because the VRM failure is not the only AC86U issue. The pink original thermal transfer pad leaks over time and thermal conductivity properties worsen. The gap between the CPU die and the heatsink is about 2.3mm. Copper shim with thermal paste on both sides will drop the temperatures 20C. Active cooling another 20C. This is a screenshot from my AC86U with shimmed CPU and 12V 120mm fan working on 9V behind the router, on the table:

View attachment 40261

Nice job Tech9! That is a pretty huge gap. Wish they would have done it right from the factory. 40c it might catch a cold at that temp might want to turn off a fan

Where did you get the copper shim? Might save me some time in case I want to tear mine apart for the fix.
For now my twin usb fans keep it out of scary temps.

 

[Tech9]

40c it might catch a cold

It stays at about 60-65C with no fan. This is one of my usual test routers.

Where did you get the copper shim?

This specific one was cut from an old AMD desktop CPU heat spreader. The thickness was right. Arctic Silver on both sides.

 

[diederik]

Hi, could you please update me if you manage to get a good dump of AC86U? I just took apart mine and I see both a UART connector and a JTAG connector.

Could you open your device non-destructively?
I have a BRT-AC828 and I want to attach an UART to its board, but so far I've only found 2 screws at the bottom back, but that doesn't seem to be enough to open the case. I realize it's a different device, but I guess Asus uses the same method across its boards (or at least similar).

 

[dominik]

Could you open your device non-destructively?
I have a BRT-AC828 and I want to attach an UART to its board, but so far I've only found 2 screws at the bottom back, but that doesn't seem to be enough to open the case. I realize it's a different device, but I guess Asus uses the same method across its boards (or at least similar).

There is plenty of videos on youtube where someone fixes asus routers, check them to see what is best methods.
On AC86 You need to remove back sticker (there are two screws under) then remove front panel (it's on plastic latches).