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Netinstall doens't work on RB951 that reboot every 9s

Posted: Mon Jul 08, 2019 6:47 pm
by agpsolutions
Hi everybody,

I have 3 RB951UI with the same problem and can't find the solution on the forum.

All routers were working and suddenly start rebooting, beeping once and blanking led 4 and 3 and than reboot again every 9 sec.

I tried to use Netinstall but even using the procedure correctly it's impossible to see them into netinstall sw because continue to reboot.

Any idea on how to solve the problem?

Thanks in advance

Andrea

Re: Netinstall doens't work on RB951 that reboot every 9s

Posted: Mon Jul 08, 2019 10:53 pm
by mkx
Did you try to replace power adapters?

Re: Netinstall doens't work on RB951 that reboot every 9s

Posted: Tue Jul 09, 2019 3:43 am
by r00t
I suppose you can't RMA them (it's too late), so it's time to open them and look inside:
Inspect all electrolytic capacitors on board, closely (with magnifier). Any signs of bulging, leaking or discoloration of PCB around them means they have to be replaced.
You can also try hooking up TTL UART to get bios console, then you can tweak some settings or at least get error message of what's going on (if it's sw fault).
UART pins are marked on the PCB, just make sure you use 3.3V TTL adapter (look for USB2TTL converter with jumper to select voltage... ones without selection are often 5V only and that will damage your RB). Examples of console access can be found by googling RB951 UART.

Re: Netinstall doens't work on RB951 that reboot every 9s

Posted: Mon Jul 15, 2019 12:56 pm
by agpsolutions
Thank you for your reply.

I have other power supply and tasted more than one (even POE) but that isn't the problem.

For RMA it's too late.

I have controlled all capacitors and seem good. I have disassembled and checked with a digital multimeter. Actually I think that it's a sw problem because happened before last upgrade when there was a system vulnerability and I hade to use netinstall for a lot of routers installed (in these cases didn't work and I changed the router)

As far as hookig TTL UART I haven't found the correct informations on google. Can you please post a link where I can find the informations how to use RB951 UART and console access?

Thanks

Andrea

Re: Netinstall doens't work on RB951 that reboot every 9s

Posted: Mon Jul 15, 2019 11:16 pm
by r00t
Here are the UART pins on the PCB (2x2 in the middle):
.jpg
They are labelled, so you know where to connect what:
You need GND, RX, TX.
Board RX ===> USB2TTL TXD
Board TX ===> USB2TTL RXD
Board GND ===> USB2TTL GND

And you want to use USB 2 TTL adapter like this:
a.jpg
It should have a jumper to select voltage to 3.3V.
Adapters that doesn't have that jumper are 5V and will damage your RB!
Always worth double-checking with a multimeter before connecting the RB...

Re: Netinstall doens't work on RB951 that reboot every 9s

Posted: Mon Jul 22, 2019 3:59 pm
by agpsolutions
Thank you for the detailed informations.

I will buy the adapter and try to solve.

Andrea