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Front panel lights

Discussion in 'ASUS AC Routers & Adapters' started by dlandiss, Sep 20, 2019.

  1. dlandiss

    dlandiss Senior Member

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    I have 2 RT-AC68U routers, the second acting as an access point. They were bought several months apart.

    The blue LEDs on the front of both have been getting dimmer, now to the point where they can barely be seen even in a dim room. Has this been observed by others? Any ideas why?

    Thanks!
     
  2. Val D.

    Val D. Senior Member

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    a) mechanical - dust accumulation
    b) electrical - failing LEDs, drivers, resistors, soldering, tracks, etc. on the PCB

    Both are fixable, depending on experience level. I used to play with routers to reduce the brightness on some models. Some manufacturers assume majority of their customers have vision problems and install the brightest LEDs they can find for cheap. :)
     
  3. Grisu

    Grisu Part of the Furniture

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    Looking at your avatar I'm just wondering.
    You should know more than most others how to solve it.
    Now they are already dead and you can only change them, and if you want lasting them forever double the resistor in series to the LEDs or turn them off if not needed.
    This is seen in many devices with LEDs that they are pushed to their limits and dying long before EOL. It is always the same problem. Too bright and dimensioned to the limits.
    And with these routeres even too high temps let them age much faster.
     
    Last edited: Sep 21, 2019
  4. bitsbytes

    bitsbytes Occasional Visitor

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    my beloved 68u's lights can barely be seen in a dark room. it's not a problem i'm worried about thought.
     
  5. dlandiss

    dlandiss Senior Member

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    Yes, especially if I had a schematic for them. Lacking a schematic it seemed prudent to ask here if others had the same issue so I didn't have to spend a week tracing printed circuit paths.

    Since all of the LEDs are displaying the same degree of dimming I doubt that it is aging, since that would not cause exactly the same degradation on 16 LEDs all at the same rate. The front panel of the router right at the LED location is 27C in a 25C ambient, so overheating also seems unlikely.

    I will probably just ignore it since I see no degradation in performance.
     
  6. Grisu

    Grisu Part of the Furniture

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    Yes thats really strange if all LEDs behave same.
    Dont think in this "IT"-forum you will get help with electronics repair.

    But all my best wishes that I am wrong and you get it solved!
    If at all I thought you would be the only one here who could help with such things. ;)
    I cant anymore - sorry, but still curious to it.
     
  7. Val D.

    Val D. Senior Member

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    All LEDs losing brightness in the same time could be indication of voltage regulator failure. There are control points on the PCB, but without electronic diagram and specifications it will be a bit challenging to find what's wrong. I would check the following:

    - power supply voltage first, must be 19V under load.
    - visual inspection of the PCB, any damage signs or something that doesn't look normal, oxidation around voltage regulators.
    - if the LEDs are anode or cathode driven. There is a resistor in series to each LED, could be on the anode or cathode side. One side of the LEDs must be connected to the GND or to VCC. It's easy to find which one it is.
    - measure LED voltage at LEDs. An oscilloscope is needed for blinking LEDs or a digital AV meter with memory. Simple AV meter won't work on a fast switching circuit (blue LEDs need >3.2V to light up). Check the Power LED voltage, it must be on constantly.
    - if voltage at LEDs is too low, find which voltage regulator is responsible for LED's and look closely at this particular one.

    Can't find ASUS repair information anywhere. Top secret products, I guess. With a bit of service information it would be a quick fix. I'm an electronic engineer, used to repair computer PCBs on a component level in the past. I can reverse engineer the router's hardware, but it's not worth the time and efforts. 2h time spend on this already exceeds the unit cost.
     
    Last edited: Sep 21, 2019
    heysoundude and Klueless like this.
  8. wouterv

    wouterv Very Senior Member

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    I have reported ages ago fading blue LED's on my RT-N66U, it seems now that the blue LED's on my RT-AC68U are not as bright as they have been.
    I would not bother at all: replacing those tiny components require at first to find the right replacement components and secondly it requires some soldering skills to actually replace them.
     
  9. dlandiss

    dlandiss Senior Member

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    Probably the path I will take unless I see performance degradation also.
     
  10. dosborne

    dosborne Senior Member

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    My ISP supplied router (SmartRG SR515ac) has a similar issue were any of the LEDs that generally come on, now only have about 15% of their original brightness even though some are always on (internet, power, DSL, etc) and some show actual activity which of course will have less "burn" time. However, some have never been "used" and retain their full brightness if I reconfigure to use that service or LAN port.

    Bottom line, I'd suspect similar scenario in this case. They essentially burn out over time. In my case, only 2 years. Pretty disappointing.

    But, the only time I actually care about the LEDs is when I have to call tech support if my DSL goes down.
     
  11. Val D.

    Val D. Senior Member

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    If some not used very often are still bright, then this is definitely LED only issue.
    If all of them appear equally dimmer though, the issue is somewhere else on the circuit.

    It's actually kind of strange because those LEDs shouldn't be overdriven. Those are indicator only LEDs and with proper current limiting resistors should last a very very long time, much longer than the usable life of the device. But many consumer devices these days are made as cheap as possible, so no wonder some engineer decided to boost the current above the specs to get a bit more brightness. I don't remember seeing dim LEDs on enterprise class products. Some servers, routers and switches work for many years and after some cleaning look like brand new. So, there is obviously a right way to engineer things.
     
  12. a5m

    a5m Occasional Visitor

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    Just happened to notice on my RT-AC68R that was purchased new in May 2016 and run 24/7 ever since that all the LEDs are kind of dim except for the one for LAN Port 3, which is noticeably brighter. I only recently (past couple of weeks) plugged something back into it after it being unused since June 2017.

    Hope this helps.
     

    Attached Files:

  13. Ronald Schwerer

    Ronald Schwerer Senior Member

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    So I guess I'll hit the switch on my 3 68Us. Two of them are in areas where I couldn't see the LEDs if I wanted (on high shelves).
     
    Grisu likes this.