Also, the large count of failing NAND blocks is not symptomatic of the 
capacitor issue.  On boards with failing caps, they will just start to randomly 
crash/halt, and as the caps continue to lose integrity, it will happen with 
increasing frequency, and eventually the boards will just fail to boot up 
entirely.

I *do* recall that there was a particular NAND chip that MikroTik started using 
in later batches of 4xx boards that people reported high failure rates of.  I 
believe MT eventually worked around the issue in software.  I think there was 
even a large wiki article about it; I'll see if I can dig it up.

On the boards that have "failed", have you tried, out of curiosity, to format 
the NAND in the bootloader and re-Netinstall?

-- Nathan

-----Original Message-----
From: mikrotik-users-boun...@wispa.org 
[mailto:mikrotik-users-boun...@wispa.org] On Behalf Of Scott Lambert via 
Mikrotik-users
Sent: Monday, October 17, 2016 4:22 PM
To: TJ Trout
Cc: Mikrotik Users
Subject: Re: [Mikrotik Users] Is anyone else losing RB493Gs?

On Mon, Oct 17, 2016 at 03:20:19PM -0700, TJ Trout wrote:
> Are you sure it's not capacitor plague? Easy to fix with a smd rework
> station

I don't see any leakage or doming of the three largeish electrolytic
capacitors on each board.  I am not even slightly tempted to attempt
to test all of the SM caps.  But I might try one or two if you have
suspects.  No SMD rework station either.

I'm actually quite happy to have the 4xx series MTU limitations leave
the network.  I just don't like spending more money for similar
performance / port count before we have to.

The affected serial numbers cover a fairly wide range.  I was hoping
to use age as a predictor, but the dead units are scattered from
25E0017443A5 to 25E0017A1420.  Assuming the numbers are actually
sequential, they are seperated by 381,051 units.  Maybe that's one
production batch?  I doubt it.

Off topic, I have one other RB493G in the dead drawer with a SN of
37970127C53D which was killed by lightning.  I'll bet that was a
different batch. :-)
 
> On Oct 17, 2016 12:55 PM, "Scott Lambert via Mikrotik-users" 
>    <mikrotik-users@wispa.org> wrote:
> 
> > We deployed a lot of RB493Gs a few years back.  They are starting show
> > 80 to 95% bad blocks on their flash storage.  I've been losing two to
> > three per month for a few months now.
> >
> > The initial symptom is the automated ssh process which gathers IP pool
> > utilization to feed MRTG starts reporting that it cannot log in.  When I
> > go to look at the problem, all users are gone and I can only log in as
> > admin with no password.  They do not survive a reboot.  But so far, if I
> > don't reboot them, they keep doing what they were supposed to do.  They
> > just allow anyone to login with the default username and password.
> >
> > So far, I've not lost any RB450Gs, but beings from the same family, I
> > half expect them to start going.  I have many fewer of those.
> >
> > I'm not upset about losing these things after 3 to 5 years. I am curious
> > if others are seeing the same thing happen on your networks.
> >
> > If others have left their RB493Gs on older firmware and are not seeing
> > issues, maybe it's a 6.30+ issue on RB493G bug?  Most of my have been
> > brought up to 6.30+ to work around some PPPoE + mangle/queue tree
> > issues.  (The MSS mangle rules don't get inserted before rule 0 leading
> > to PathMTU issues.)
> >
> > If it is happening to others, maybe I need to order 16 to 21
> > replacements and do some preventative swaps.
> >
> > "RouterOS RB493G","6.34.6"
> > "RouterOS RB493G","6.32.3"
> > "RouterOS RB493G","6.34.4"
> > "RouterOS RB493G","6.7"
> > "RouterOS RB493G","6.32.3"
> > "RouterOS RB493G","6.34.6"
> > "RouterOS RB493G","6.34.6"
> > "RouterOS RB493G","6.30.4"
> > "RouterOS RB493G","6.34.4"
> > "RouterOS RB493G","6.30.4"
> > "RouterOS RB493G","6.32.3"
> > "RouterOS RB493G","6.18"
> > "RouterOS RB493G","6.18"
> > "RouterOS RB493G","6.7"
> > "RouterOS RB493G","6.18"
> > "RouterOS RB493G","6.30.4"
> >
> > "RouterOS RB450G","6.7"
> > "RouterOS RB450G","6.32.3"
> > "RouterOS RB450G","6.32.3"
> > "RouterOS RB450G","6.34.6"
> > "RouterOS RB450G","6.34.6"
> > "RouterOS RB450G","6.27"
> > "RouterOS RB450G","6.34.3"
> >
> > --
> > Scott Lambert                    KC5MLE                       Unix SysAdmin
> > lamb...@lambertfam.org
> > _______________________________________________
> > Mikrotik-users mailing list
> > Mikrotik-users@wispa.org
> > http://lists.wispa.org/mailman/listinfo/mikrotik-users
> >

-- 
Scott Lambert                    KC5MLE                       Unix SysAdmin
lamb...@lambertfam.org
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