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fragtion
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Joined: Fri Nov 13, 2009 10:08 pm
Location: Johannesburg, South Africa

Old SXT 5HnD doesn't always boot up

Sat Apr 09, 2022 4:23 pm

Hi

I have an old SXT 5HnD which has served me well over the years

Lately when I plug in the PoE, it's hit-or-miss whether the device boots up

Symptoms:
1) The single initial "beep" doesn't always sound
2) Only LD1600 LED illuminates. On a good boot, the LD600 LED will also glow while the device beeps.

Unplugging and replugging the PoE cable can sort out the problem, after which the device will run normally again

I've tried different PoE voltages and cables.
I also tried a full netinstall, and forcing backup booter, but it doesn't change the issue
The problem seems to be with a component on the PCB ... ?

Device has a history of being on a tower where lightning damage / ESD was a common occurrence, however there are no signs of lightning damage and once it manages to boot everything runs normally.

I removed the PCB from the SXT enclosure and can't see any visible signs of liquid damage, although the enclosure is yellowed and the plastic aged/brittle (I'm looking to replace the enclosure too)

I'd like to try repair the device to make it boot up reliably again. Anyone with Mikrotik & Electronics knowledge maybe know what I should look out for ?

Edit: Could this be the problem? Is this a normal system voltage for SXT powered by 12v PoE ?
[admin@MikroTik] > /system/health/print 
Columns: NAME, VALUE, TYPE
#  NAME         VALUE  TYPE
0  voltage      9.6    V   
1  temperature  29     C   
[admin@MikroTik] > 
Edit#2: So I don't think it's the power supply because with 24v PoE there's enough voltage, but still the device doesn't beep once/boot reliably each time I plug in the PoE:
[admin@MikroTik] > /system/health/print 
Columns: NAME, VALUE, TYPE
#  NAME         VALUE  TYPE
0  voltage      19.4   V   
1  temperature  30     C   
[admin@MikroTik] > 

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