Ubiquiti US-16-150 Help

**shovenose** · 08-20-2021, 12:06 AM

Got this dead Unifi US-16-150W, assuming it was the power supply. Alas the PSU and everything looks perfect and the PSU is outputting a solid 53V.

I noticed that upon disconnecting then reconnecting the 4-pin connector from the PSU to the switch's mainboard it makes quite a spark. More than I would expect. So I got curious, took the mainboard out, and found the bottom to be like this.

Is this water damage? Or something else? Should I try to clean it off? Or is it toast?

**sam_sam_sam** · 08-20-2021, 01:37 AM

Try cleaning up with denatured alcohol and see if you can clean or use a good flux remover spray I have clean a few boards with a flux remover spray

https://www.mpja.com/Flux-Remover-41...info/30364+MG/

It might be water stains but I not completely sure about this

**stj** · 08-20-2021, 03:55 AM

thats residue from water soluable flux,
the factory isnt changing the water often enough.

**shovenose** · 08-20-2021, 09:04 AM

Gotcha, thanks, do you think there is any point in cleaning it? Or is something else wrong with it?

**shovenose** · 08-20-2021, 09:43 AM

Alright, so I did a little testing.

I've attached a couple pictures. I have a solid 24V across the purple caps. This is probably the circuit for the 24V Passive PoE function.

More important, in the other pic across the two points right below the pink dot I have fluctuating 0 to 3.3V. I'm assuming this is a/the problem.

What can I check to see why the 3.3V is fluctuating like that?

**Per Hansson** · 08-21-2021, 12:03 AM

Most likely something is shorted and the power supply is hiccuping: that is it senses the short, powers down and then tries again...
Some times such a short can be found by a thermal camera (or hand) or you can use a very sensitive multimeter in ohms mode.

**shovenose** · 08-21-2021, 12:20 AM

Quote:

Originally Posted by Per Hansson

Most likely something is shorted and the power supply is hiccuping: that is it senses the short, powers down and then tries again...
Some times such a short can be found by a thermal camera (or hand) or you can use a very sensitive multimeter in ohms mode.

Hmm, thing is the power supply is happily at 53.7V with absolutely no fluctuating the entire time.

**Per Hansson** · 08-21-2021, 01:18 AM

I mean on the secondary side, the 3.3v power supply.

**CapLeaker** · 08-21-2021, 04:57 AM

Probably there are no shorts on the 3.3V rail. I think there is something else that gets powered from the 3.3V rail that shorts out when powered up. Check the other buck converters. Power the 3.3V up with a bench power supply and see what happens...

**shovenose** · 08-21-2021, 11:07 AM

Quote:

Originally Posted by CapLeaker

Probably there are no shorts on the 3.3V rail. I think there is something else that gets powered from the 3.3V rail that shorts out when powered up. Check the other buck converters. Power the 3.3V up with a bench power supply and see what happens...

Hmm, OK, I'll have to rig something up.

In the meantime, I found this bubble on one of the BCM59111KMLG chips. It's supposedly a 60W PoE controller. Is this normal? Or bubbles=bad?

**CapLeaker** · 08-21-2021, 11:16 AM

That chip is the problem I’d say.

**shovenose** · 08-22-2021, 08:09 AM

Quote:

Originally Posted by CapLeaker

That chip is the problem I’d say.

Thank you, I will see what I can do. I wonder if it's going to be really hard to remove lol.

**Th3_uN1Qu3** · 08-22-2021, 08:56 AM

Quote:

Originally Posted by shovenose

Hmm, OK, I'll have to rig something up.

In the meantime, I found this bubble on one of the BCM59111KMLG chips. It's supposedly a 60W PoE controller. Is this normal? Or bubbles=bad?

It's dead Jim. That's a burn mark alright. Look also at the discoloration on the PCB around it.

Speaking of removal, depending on the power of your hot air station, you may need to use some sort of preheater or hotplate, that chip is a QFN with a large heat dissipation pad underneath.

**CapLeaker** · 08-22-2021, 01:51 PM

Shouldn’t be that hard to remove. You can always preheat the board, then take it off with hot air gun.

**Th3_uN1Qu3** · 08-22-2021, 01:55 PM

It's easy peasy if you preheat, just don't be surprised if a cheapo chinese SMD rework station alone won't cut it.

**shovenose** · 08-22-2021, 06:57 PM

Quote:

Originally Posted by Th3_uN1Qu3

It's easy peasy if you preheat, just don't be surprised if a cheapo chinese SMD rework station alone won't cut it.

it better be good enough because that's what i ordered haha. i will update once i've tried it.

**shovenose** · 08-27-2021, 10:29 AM

Quote:

Originally Posted by Th3_uN1Qu3

It's easy peasy if you preheat, just don't be surprised if a cheapo chinese SMD rework station alone won't cut it.

so, i got my cheapo smd rework station and it worked perfectly to remove the chip.

i was hoping i'd get at least some sign of life now that the chip is removed and presumably the short is too.

unfortunately its still dead. what can i check now :'(

**stj** · 08-27-2021, 11:45 AM

check for shorted ceramic caps near the dead chip area.

**CapLeaker** · 08-27-2021, 01:45 PM

Check your wonky power rail. See what it does now?

08-20-2021, 01:37 AM	#2
sam_sam_sam Badcaps Veteran Join Date: Jul 2011 City & State: Some times Sunny Jacksonville FL My Country: USA Line Voltage: 120 Volts 60 HZ I'm a: Knowledge Seeker Posts: 2,973	Re: Liquid damage or somethign else? Try cleaning up with denatured alcohol and see if you can clean or use a good flux remover spray I have clean a few boards with a flux remover spray https://www.mpja.com/Flux-Remover-41...info/30364+MG/ It might be water stains but I not completely sure about this __________________ 9 PC LCD Monitor 6 LCD Flat Screen TV 30 Desk Top Switching Power Supply 10 Battery Charger Switching Power Supply for Power Tool 6 18v Lithium Battery Power Boards for Tool Battery Packs 1 XBox 360 Switching Power Supply and M Board 25 Servo Drives 220/460 3 Phase 6 De-soldering Station Switching Power Supply 1 Power Supply 1 Dell Mother Board 15 Computer Power Supply 1 HP Printer Supply & Control Board * lighting finished it * These two repairs where found with a ESR meter...> Temp at 50F then at 90F the ESR reading more than 10% 1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later ) 2 Hem Saw Computer Stack Board All of these had CAPs POOF All of the mosfet that are taken out by bad caps Last edited by sam_sam_sam; 08-20-2021 at 01:41 AM..

08-20-2021, 03:55 AM	#3
stj Great Sage 齊天大聖 Join Date: Dec 2009 City & State: Europe My Country: some shithole run by Israeli agents I'm a: Professional Tech Posts: 25,390	Re: Liquid damage or somethign else? thats residue from water soluable flux, the factory isnt changing the water often enough.

08-20-2021, 09:04 AM	#4
shovenose Send Doge Memes Join Date: Aug 2010 City & State: Vallejo, California My Country: USA I'm a: Forum Junkie Posts: 6,323	Re: Liquid damage or somethign else? Gotcha, thanks, do you think there is any point in cleaning it? Or is something else wrong with it?

08-21-2021, 12:03 AM	#6
Per Hansson Super Moderator Join Date: Jul 2005 City & State: ---- My Country: Sweden Line Voltage: 230v 50Hz I'm a: Knowledge Seeker Posts: 4,842	Re: Ubiquiti US-16-150 Help Most likely something is shorted and the power supply is hiccuping: that is it senses the short, powers down and then tries again... Some times such a short can be found by a thermal camera (or hand) or you can use a very sensitive multimeter in ohms mode. __________________ "The one who says it cannot be done should never interrupt the one who is doing it."

08-21-2021, 01:18 AM	#8
Per Hansson Super Moderator Join Date: Jul 2005 City & State: ---- My Country: Sweden Line Voltage: 230v 50Hz I'm a: Knowledge Seeker Posts: 4,842	Re: Ubiquiti US-16-150 Help I mean on the secondary side, the 3.3v power supply.

08-21-2021, 04:57 AM	#9
CapLeaker Leaking Member Join Date: Dec 2014 City & State: Atlantic Canada My Country: Canada Line Voltage: Ground, 0Hz I'm a: Hobbyist Tech Posts: 4,820	Re: Ubiquiti US-16-150 Help Probably there are no shorts on the 3.3V rail. I think there is something else that gets powered from the 3.3V rail that shorts out when powered up. Check the other buck converters. Power the 3.3V up with a bench power supply and see what happens...

08-21-2021, 11:16 AM	#11
CapLeaker Leaking Member Join Date: Dec 2014 City & State: Atlantic Canada My Country: Canada Line Voltage: Ground, 0Hz I'm a: Hobbyist Tech Posts: 4,820	Re: Ubiquiti US-16-150 Help That chip is the problem I’d say.

08-22-2021, 01:51 PM	#14
CapLeaker Leaking Member Join Date: Dec 2014 City & State: Atlantic Canada My Country: Canada Line Voltage: Ground, 0Hz I'm a: Hobbyist Tech Posts: 4,820	Re: Ubiquiti US-16-150 Help Shouldn’t be that hard to remove. You can always preheat the board, then take it off with hot air gun.

08-22-2021, 01:55 PM	#15
Th3_uN1Qu3 Believe in Join Date: Jul 2010 City & State: Bucharest My Country: Romania Line Voltage: 230VAC 50Hz I'm a: Professional Tech Posts: 5,563	Re: Ubiquiti US-16-150 Help It's easy peasy if you preheat, just don't be surprised if a cheapo chinese SMD rework station alone won't cut it.

08-27-2021, 11:45 AM	#18
stj Great Sage 齊天大聖 Join Date: Dec 2009 City & State: Europe My Country: some shithole run by Israeli agents I'm a: Professional Tech Posts: 25,390	Re: Ubiquiti US-16-150 Help check for shorted ceramic caps near the dead chip area.

08-27-2021, 01:45 PM	#19
CapLeaker Leaking Member Join Date: Dec 2014 City & State: Atlantic Canada My Country: Canada Line Voltage: Ground, 0Hz I'm a: Hobbyist Tech Posts: 4,820	Re: Ubiquiti US-16-150 Help Check your wonky power rail. See what it does now?

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