Need help with 24V power supply

[Heyun]

Hi,
We have tried to use 24V power supply to the RS board but it failed to
start up. There is no problems when use 12V power supply.
The error messages are as following:
Looks like the RESET button is malfunctioning when the input voltage is 24V!

.+
ADM6996FC PHY found on MAC0
ADM6996FC PHY found on MAC1
Ethernet eth0: MAC address 00:15:6d:c1:2a:8d
IP: 192.168.1.20/255.255.255.0, Gateway: 0.0.0.0
Default server: 192.168.1.42

RedBoot(tm) bootstrap and debug environment [ROMRAM]
Ubiquiti Networks certified release, version 0.9.8.04 - built 15:47:39, Dec 15 2008

Copyright (C) 2000, 2001, 2002, 2003, 2004 Red Hat, Inc.

Board: Ubiquiti AR71xx-based board
RAM: 0x80000000-0x84000000, [0x00000000-0x00000000] available
FLASH: 0xbf000000 - 0xc0000000, 256 blocks of 0x00010000 bytes each.

RESET button pressed, starting rescue mode...
TFTPD initialized on 192.168.1.20/255.255.255.0 port: 69 (Memory: [0x8006cc00-0x83fe1000])
TFTPD: waiting for connection...
TFTPD: waiting for connection...
TFTPD: waiting for connection...
TFTPD: waiting for connection...
TFTPD: waiting for connection...
TFTPD: waiting for connection...
TFTPD: waiting for connection...
TFTPD: waiting for connection...
TFTPD: waiting for connection...
TFTPD: waiting for connection...
TFTPD: waiting for connection...
TFTPD: waiting for connection...
TFTPD: waiting for connection...
TFTPD: waiting for connection...
'cfg' not found - nothing to reset!
TFTPD: waiting for connection...
'cfg' not found - nothing to reset!
TFTPD: waiting for connection...
'cfg' not found - nothing to reset!
TFTPD: waiting for connection...
'cfg' not found - nothing to reset!
TFTPD: waiting for connection...
'cfg' not found - nothing to reset!
TFTPD: waiting for connection...
'cfg' not found - nothing to reset!
TFTPD: waiting for connection...
'cfg' not found - nothing to reset!
TFTPD: waiting for connection...
'cfg' not found - nothing to reset!
TFTPD: waiting for connection...
'cfg' not found - nothing to reset!
TFTPD: waiting for connection...
'cfg' not found - nothing to reset!
TFTPD: waiting for connection...
'cfg' not found - nothing to reset!
TFTPD: waiting for connection...
'cfg' not found - nothing to reset!
TFTPD: waiting for connection...
'cfg' not found - nothing to reset!
TFTPD: waiting for connection...

[freezer2k]

Do you have a multimeter?

Try to measure the actual output voltage of your power supply, maybe you overvoltage?

[UBNT-Mike.Ford]

Hello,

Please measure the output votlage of your power supply and post the exact value.

Thanks,

Mike

[blueandwhiteg3]

I've never had any power issues when I am within the proper voltage range, and even a little bit outside it. I agree you should take a voltage measurement with a good multimeter and go from there.

Also, remember that it may be possible for other factors not easily seen on a basic multimeter to cause problems. I would suggest you try another power adapter if the multimeter results look good but it still won't behave.

[WHT]

This is why we use a simple $40 analog VOM meter with a meter movement. Far more reliable accuracy, over a digital multimeter.

[Heyun]

Thanks for the helps.
We have found the root cause of the failed startup under 24V. It was the Ethernet cable used between POE and board. When we changed that 15 meter cable and the board worked fine both under 12V and 24V.

[UBNT-Mike.Ford]

Thanks for the update.

Mike