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jacobalberty
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Bricked RB751U-2HnD?

Fri Sep 30, 2011 12:23 am

I had this item shipped to work, I picked it up today and tested it briefly at work. Item worked fine I then brought it home and when I plugged it in all 5 Ethernet interface lights (but not the wireless interface light), the power light and possibly the ACT light were blinking in Unison. I attempted to use the reset button as indicated in the quick setup guide to initiate a configuration reset, then I attempted to do a netinstall, both did not work. Plugging it into another device either ethernet card on a laptop or network switch on a laptop result in the other device not detecting the routerboard and no change in the lights blinking.

Is my routerboard bricked already? I emailed the supplier I purchased it from already but It's already pretty late in the day so I'll wait till tomorrow to try calling them. But I was hoping someone here might have seen this in another routerboard and have some idea what happened.
 
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Re: Bricked RB751U-2HnD?

Fri Sep 30, 2011 9:07 am

Well, that was fast. Probably, you're the first with a bricked RB751.

Did you actually modified something in the config, while you tested it at work, or just plugged in, logged in, logged out, pulled out the power supply? Maybe the RB751 was saving something into the flash, while you unplugged it.
 
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Re: Bricked RB751U-2HnD?

Fri Sep 30, 2011 5:09 pm

I also had one of my first pair of RB751U-2HnD die within the first 3 hours of receiving it on Wednesday.

Did a full config, was running fine for about 2 hours, then everything dropped. All the lights on the device were blinking in unison, about 3-4 blinks per second. No amount of adding or removing power, waiting for the device to discharge/cooldown, or use of the reset/netinstall mechanisms got any response.

On the plus side, its partner has been running without incident for almost 48 hours now. My RMA unit is on its way from my reseller, so hopefully, it's just a normal incident of a bad unit. Time will tell.
 
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Re: Bricked RB751U-2HnD?

Tue Oct 11, 2011 1:48 pm

That's quite sad if the 751 has some kind of series / product failure, because I've just ordered some days ago my unit online.

Hopefully I won't face this problem.
 
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Re: Bricked RB751U-2HnD?

Wed Oct 12, 2011 2:33 am

Here's another power oddity with the RB751U.

Connect ethernet port 2, 3, 4, or 5 to an 802.3af POE switch. Then connect an 802.3af POE device like a VoIP phone to one of other ethernet ports 2, 3, 4 or 5 on the same RB751U. You'll notice that the POE device will start into a loop of power cycling. I did this test with a Dell 3548P and a Polycom IP331 phone. This doesn't occur with an RB750GL.

This might or might not have anything to do with the other power issues on the device, but there is clearly some oddities here. I don't think power should be leaking between ethernet ports.
 
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Re: Bricked RB751U-2HnD?

Mon Oct 17, 2011 1:21 pm

Please contact the seller for RMA repair/replacement if you run into any issues, just like with any other device. Changing the PSU is not recommended, as it doesn't completely solve the issue, the unit still needs repair.
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Re: Bricked RB751U-2HnD?

Mon Oct 17, 2011 7:46 pm

The new AC adapter arrived on Friday, but I didn't get a chance to test it until today. The good news is everything is working again!

Thanks again to Tom at http://roc-noc.com for addressing the problem so quickly!

I came here to share my results and saw this post from normis:
Please contact the seller for RMA repair/replacement if you run into any issues, just like with any other device. Changing the PSU is not recommended, as it doesn't completely solve the issue, the unit still needs repair.
So now I am confused about what to do with my device. I am also curious if the device comes with a warranty. I could not seem to find this information at the http://routerboard.com/ site.

I was hoping to get some feedback from others who have experienced the same problem and fixed it by using a different AC adapter. Are you planning to keep the device or request an RMA? Also what AC adapter are you using day-to-day, the supplied one or a different one?

I feel bad now asking Tom for an RMA after he went through the trouble of sending out a new AC adapter which fixed the problem. But I also don't want to have a problem 6 months down the road and not be able to get a replacement.
 
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Re: Bricked RB751U-2HnD?

Mon Oct 17, 2011 7:54 pm

Hey Normis, are you able to confirm if the problem means there is something wrong with those boards or can it simply be resolved for good by using a higher voltage power supply?
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Re: Bricked RB751U-2HnD?

Tue Oct 18, 2011 12:25 am

Yes could you expand upon what not completely resolving the problem means?

After getting mine functional again it has been running fine on the factory adapter since.
It's had lots of configuration time and reboots since then as well and no more blinking lights
yet.
 
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normis
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Re: Bricked RB751U-2HnD?

Tue Oct 18, 2011 8:05 am

The high power adapter will not solve the issue. We are working on making a procedure for this case, please contact the seller for more details. They will be informed in the next few days.
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Re: Bricked RB751U-2HnD?

Tue Oct 18, 2011 9:08 pm

please contact the seller for more details
Does that mean, that you found the source of this problem, and it require hw modification to solve it?
 
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Re: Bricked RB751U-2HnD?

Tue Oct 18, 2011 9:30 pm

00:00:15 system,error,critical router was rebooted without proper shutdown (cause 1) 
Mine has been acting up occasionally too, but I won't look a gift horse in the mouth :-)

Normis: should we send in supout's or do you have all the information you need?
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Re: Bricked RB751U-2HnD?

Wed Oct 19, 2011 8:20 am

and it require hw modification to solve it?
yes, like I said, RMA repair is needed, and power supply changing is not fixing anything
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Re: Bricked RB751U-2HnD?

Wed Oct 19, 2011 8:21 am

Normis: should we send in supout's or do you have all the information you need?
not sure about this one, send some supout.rif files please
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Re: Bricked RB751U-2HnD?

Wed Oct 19, 2011 10:33 pm

and it require hw modification to solve it?
yes, like I said, RMA repair is needed, and power supply changing is not fixing anything
So, you already know the root of the problem? Can this be repaired at home with the necessary tools?

I've just received my RB751, after a lot of waiting, and I don't really want to spend time with waiting another one month for a spare unit. Also, this information will be handy, if we face this failure after warranty.
 
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Re: Bricked RB751U-2HnD?

Thu Oct 20, 2011 8:31 am

So, you already know the root of the problem? Can this be repaired at home with the necessary tools?
I'm sorry but it's not possible to repair at home.
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Re: Bricked RB751U-2HnD?

Thu Oct 20, 2011 11:12 pm

Then let me ask this an another way.

Do you know the root cause of the problem? You did not answered this.
What if I will send back my bricked 751, and after ~ 1 month, I will get an another one with the same defect?
 
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Re: Bricked RB751U-2HnD?

Fri Oct 21, 2011 1:35 am

Then let me ask this an another way.

Do you know the root cause of the problem? You did not answered this.
What if I will send back my bricked 751, and after ~ 1 month, I will get an another one with the same defect?
We cover the warranty for 1 year as do most other distributors, so yes you would get a replacement. No, it should not have the same defect.

Mikrotik is working on a way for distributors to easily identify the bad units. We are still waiting for this information. Yes they have identified the cause of the problem.

This is a new product and there is always risk of bugs or defects with new products. Please be patient with them.

Tom
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Re: Bricked RB751U-2HnD?

Fri Oct 21, 2011 7:17 am

Thank you for the detailed answer!
 
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Re: Bricked RB751U-2HnD?

Mon Oct 24, 2011 2:08 am

I received one of these at MUM and it is doing the same thing (Blinking lights). How do I get an RMA for it?
Thanks
 
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Re: Bricked RB751U-2HnD?

Tue Oct 25, 2011 4:12 pm

Any update on how to identify the bad units?
 
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Re: Bricked RB751U-2HnD?

Thu Oct 27, 2011 12:29 pm

Please email support if you received such bad device at the MUM! support@mikrotik.com
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Re: Bricked RB751U-2HnD?

Thu Jan 12, 2012 9:12 am

Then let me ask this an another way.

Do you know the root cause of the problem? You did not answered this.
What if I will send back my bricked 751, and after ~ 1 month, I will get an another one with the same defect?
We cover the warranty for 1 year as do most other distributors, so yes you would get a replacement. No, it should not have the same defect.

Mikrotik is working on a way for distributors to easily identify the bad units. We are still waiting for this information. Yes they have identified the cause of the problem.

This is a new product and there is always risk of bugs or defects with new products. Please be patient with them.

Tom
That is some great information. If Mikrotik is working on a way (or hopefully by now, has come up with a way) for distributors to easily identify the bad units, I would love to be able to test my other (9) RB751's to make sure they are ok before putting them out for retail clients where one of mine bricked in less than a week just using it at my own office. Any documentation on that would be much appreciated!

Thank you for your time and assistance.
 
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Re: Bricked RB751U-2HnD?

Thu Jan 12, 2012 9:25 am

turn them on. if there is no blinking - they are fine. that's it.
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Re: Bricked RB751U-2HnD?

Sat Jan 14, 2012 6:05 pm

The problem with your reply Normis is the issue will start not necessarily the first boot.
We use these for commercial sales so so far, not a good thing to happen but the product is good.

I bought 60 for my customers because it works very good with the IPAD.
 
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Re: Bricked RB751U-2HnD?

Mon Jan 16, 2012 8:17 am

This is a very limited issue, it only affects the very first devices. Our of all manufactured RB751s, the affected percentage is miniscule. You should stop worrying about it. We fixed the issue already in October! That's around the time they started shipping!
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Re: Bricked RB751U-2HnD?

Mon Sep 10, 2012 4:38 am

3 of my last 4 bricked. One out of the box first boot, one in two days uptime, third in two weeks.
Any serial numbers for bad boards?
 
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Re: Bricked RB751U-2HnD?

Fri Sep 14, 2012 4:39 pm

Application of 24v to the board seemed to bring them back from the dead.
 
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Re: Bricked RB751U-2HnD?

Sun Sep 23, 2012 5:02 pm

...but only temporarily, unfortunately. Went into seizure mode after 2 days in service.
 
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Re: Bricked RB751U-2HnD?

Mon Sep 24, 2012 4:44 pm

...but only temporarily, unfortunately. Went into seizure mode after 2 days in service.
please contact support@mikrotik.com and write the Serial numbers of thos board so we could check if they could be affected by that problem.
 
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Re: Bricked RB751U-2HnD?

Mon Sep 24, 2012 5:44 pm

...but only temporarily, unfortunately. Went into seizure mode after 2 days in service.
please contact support@mikrotik.com and write the Serial numbers of thos board so we could check if they could be affected by that problem.
Done. Thank you
 
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Re: Bricked RB751U-2HnD?

Fri Oct 05, 2012 1:15 am

This is a very limited issue, it only affects the very first devices. Our of all manufactured RB751s, the affected percentage is miniscule. You should stop worrying about it. We fixed the issue already in October! That's around the time they started shipping!
Normis, i doubt that. We just bought 5 of the RB751 devices and one of them is having this blinking and not coming up (it worked for 2 minutes after first powering it and then it crashed and since then its dead). The other devices all have 5.16 installed which was released in May 2012 and i dont think that the distributor updated them before shipping.

Is this (known) issue always a DOA or can it happen anytime? :(

Regards,
Joerg
 
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Re: Bricked RB751U-2HnD?

Fri Oct 05, 2012 1:49 am

This is a very limited issue, it only affects the very first devices. Our of all manufactured RB751s, the affected percentage is miniscule. You should stop worrying about it. We fixed the issue already in October! That's around the time they started shipping!
Normis, i doubt that. We just bought 5 of the RB751 devices and one of them is having this blinking and not coming up (it worked for 2 minutes after first powering it and then it crashed and since then its dead). The other devices all have 5.16 installed which was released in May 2012 and i dont think that the distributor updated them before shipping.

Is this (known) issue always a DOA or can it happen anytime? :(

Regards,
Joerg
As far as I can tell, it can happen anytime. I had two boards ready to RMA back to my vendor (on MT's advice). One was DOA with flashing LEDs, the other was programmed and put into service but developed flashing light syndrome after one day-no reboot or power cycle involved.
I decided to power them back up one last time before I dropped them in the mail. Used a 24v POE. They both booted up normally. I switched to the shipped 12v power supply and they both rebooted normally.
I find it very hard to believe that all the 751U's I've bought over the last year are all part of "the very first devices". According to MT support, they do not have a serial number list of affected boards. It's a very annoying and random problem it seems. The easy answer is "stuff breaks-send them back". But in my experience they can develop this problem at random and anytime. The answer Normis gave that if you power them up and they boot normally, don't worry, they are fine is not correct.
 
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Re: Bricked RB751U-2HnD?

Thu Oct 11, 2012 2:53 am

I received one today and opened it, updated it to 5.20 run for about 3 hours and BOOM lights blinking. Should i get another type router.
 
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Re: Bricked RB751U-2HnD?

Thu Oct 11, 2012 3:24 am

I received one today and opened it, updated it to 5.20 run for about 3 hours and BOOM lights blinking. Should i get another type router.
Probably about time for an MT staff comment...
 
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Re: Bricked RB751U-2HnD?

Thu Oct 18, 2012 4:20 pm

Reveived 5 pcs yesterday, all dead, all leds blinking. Sent mail to support.

So it is not correct that this issue was solved!
 
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Re: Bricked RB751U-2HnD?

Thu Oct 18, 2012 4:26 pm

100% broken????? WOW!!

It seems that there is no real quality control :(
 
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Re: Bricked RB751U-2HnD?

Thu Oct 18, 2012 4:27 pm

100% broken????? WOW!!

It seems that there is no real quality control :(
sounds highly unlikely, maybe something else was wrong. will check that ticket
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Re: Bricked RB751U-2HnD?

Thu Oct 18, 2012 4:50 pm

well.. what "something else" should it be??
 
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Re: Bricked RB751U-2HnD?

Thu Oct 18, 2012 5:08 pm

Reflashed the fw by netinstall on 4 units with 24V connected power supply and now working OK with shipped power supply.

The worst thing Mikrotik can do is not to tell anyone what is the problem and just say RMA.

You need to understand that we are not just buying/selling, but we are installing and this costs us money because we send technicians and also reputation is not good.

I'm leaving these 4 pcs for internal use and not buying anymore. 1 pcs was allready sent for RMA and they report they will reflash it.

These units were working OK, configured by quick-set, updated FW do 5.21, after they were taken to customers site, the did not start anymore.
 
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Re: Bricked RB751U-2HnD?

Thu Oct 18, 2012 5:12 pm

It would be nice if a MT guy (normis?) could let us know WHY that "workaround" with a 24V powersupply is helping?! My guess is that some of the hardware-components are really bad?!
 
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Re: Bricked RB751U-2HnD?

Thu Oct 18, 2012 5:16 pm

Just got confirmed from the distributor doing RMA, that they only reflashed it and I can pick it up today.

So, I'm really confused.

This is the behaviour.

http://www.youtube.com/watch?v=_2fHNR8s1BM
 
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Re: Bricked RB751U-2HnD?

Thu Oct 18, 2012 11:21 pm

Got an RB751U-2HnD in the mail today. Guess what? It worked for approximately 2 minutes before it died.
 
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Re: Bricked RB751U-2HnD?

Fri Oct 19, 2012 8:12 am

All of you, please send serial numbers to support
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Re: Bricked RB751U-2HnD?

Mon Nov 12, 2012 1:09 am

Hello all,
I just had the same incident during routine configuration - all the LEDs started flashing.
However, there's a little twist to it: I noticed that there was a slight smell of overheated plastic and chemicals, which later disappeared.

The funny thing is that it revived spontaneously after a couple of minutes when I reconnected the PSU (the original one). It does seem to function properly now, but any confidence in its reliability is lost.

Normis, could you please confirm where should we send the serial numbers? I have 5 new 751s and would like to RMA them before deployment, as well as try and avoid getting the faulty ones again since I plan to get 30 more.

Also, I think that MT owes us an explanation! Is this a fire hazard? Any hazardous emissions in that suspicious smelling smoke?

best regards,
Djordje
 
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Re: Bricked RB751U-2HnD?

Fri Jan 25, 2013 1:53 am

Hello, I see the last post on this was back in November 2012 and I am wondering if there was anymore updates from MT on this? I just bought an RB751, updated it to router os 6.07 and firmware of 3.12. Wireless was working great, unplugged the unit, plugged back in with ethernet cables connected and unit started flashing lights and then died. Is it worth doing an RMA, or should I just get a refund?

Thanks

Jeremy
 
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Re: Bricked RB751U-2HnD?

Fri Jan 25, 2013 2:09 am

Apparently the defective ones are still out there waiting to bite you. I'd return it to your vendor or RMA to MT.
 
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Re: Bricked RB751U-2HnD?

Tue Apr 30, 2013 3:20 pm

Well we bought 17 RB751 on the company, and 9 of them are bricked, but we needed all for a project so we look for a solution, apparently when its powered for 6 mins, something burnout (we dont open it, we smell something burned on the inside) all the leds start to blink, so we have tryied another thing to make react it, we take a PoE adaptor from an SXT and try to powerup with that, the first one didnt work, when we put the 2 powers (Jack and PoE) the RB start to work, really strange, we have a Laptop with PoE,(done by ourselves) the 8 after the first one where fixed with the PoE from the laptop only, strange thing, now we are doing some tests to see how much time they can work, because we think the brick can happen again.

If u are on despair, you can try this solution, like we were and tried.

BR
Requium
 
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Re: Bricked RB751U-2HnD?

Tue Apr 30, 2013 4:40 pm

Requium
Please return RB751 to RMA, that are not working properly with the standard power adapter (that is included in the box).
 
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Re: Bricked RB751U-2HnD?

Tue Apr 30, 2013 4:44 pm

sergejs,

can you confirm that it is only an issue with the "default"-powersupply that is included and can be fixed with another one?

- Joerg
 
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Re: Bricked RB751U-2HnD?

Sat May 04, 2013 9:02 pm

So, does this mean that even though "the issue was fixed in October 2011", that if we buy these units today (May 2013), that they STILL could have this problem???

How can this issue still be around 18 months after it was "fixed" ???
 
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Re: Bricked RB751U-2HnD?

Tue May 07, 2013 3:34 pm

Already tested for more than a week an they are wor toakwking well with the power adaptor which they come dunno what happen but they react with after i used the poe, I can't sent 15 RB to RMA I will lose my client in the time, I justuse the poe to make it react nothing more after that I'm using they're own power adaptor.

BR
 
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Re: Bricked RB751U-2HnD?

Fri May 10, 2013 12:12 pm

Back during the 2011 Las Vegas MUM, I received an RB751U that did the same thing: worked for about 24 hours, then did the "blinking lights" thing. I hooked up a different power supply to it, and then it started working again. So I hooked the original power supply back up, and it still worked with that! After hooking up the different power supply to it (also 12V, but more amperage), I also noticed the burning smell that others here have commented about, and even noticed a small puff of smoke escape from the device! After that happened, the "blinking lights" problem stopped and it seemed to act normally.

I mentioned this to Normis at MUM, and he told me that they didn't know yet what caused it but they had one back at headquarters in Latvia that was doing the same thing that they were studying. I guess I should have asked for them to swap out my 751U, but I did not. Amazingly, it is still working to this day; I am posting this message to the forums while connected to it!

Normis has made two claims in this thread:

1) Switching power supplies is not a fix. The routers with this problem still need to be repaired.
2) This problem only occurred in early batches, and was fixed very quickly in newer batches.

#1 makes sense. The "puff of smoke" suggests that something in the router is burning up and was probably defective to begin with. Interestingly, though, we have run into a few 751U routers that had the exact same thing happen to them, and in each case, after the "puff of smoke", the router starts working normally again and continues to do so indefinitely!

#2, though, is unfortunately not true. We have run into several 751U routers that do this, even recent ones. I know that some of the routers we received with this problem more recently are newly-manufactured ones that came out after MikroTik claims they fixed the problem, and I know this for the following reasons:

1) The MAC address begins with D4:CA:6D, not 00:0C:42
2) The MMCX connector on the front sticks out like the new ones, instead of being flush with the case like the old ones

So there are still RB751U being manufactured that have this problem. Fortunately it does seem to be a small percentage.

The question that still remains is, what exactly is going on with these routers? There must be a defective component that is perhaps drawing too much power, and eventually burning itself out (?).

The last time we ran into a router with the "blinking lights", I decided to take it apart before I plugged a different power supply into it, so that I could see where the smoke was coming from. When I plugged the new power supply in with the plastic case off, I saw that the smoke came from underneath the wireless RF shield. Unfortunately, I did not think to remove the RF shield before applying power to the board, so I was not able to see what burned up underneath the shield. I removed the shield after the smoke was gone, but I didn't see any burn marks or charring. The next time I run across one doing the "blinking lights" dance, I will tear it apart AND remove the RF shield before applying power, and be careful to observe exactly what is burning up.

Whatever it is, though, it apparently has something to do with the wireless part of the RouterBOARD. Is it the amplifier?

-- Nathan

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