Dell PowerConnect 2716 and ADP-40VP PSU recap

[Per Hansson]

This switch power LED was lit red and some ports with cables not even in them where lit yellow after a power outage, not a good sign...

I checked the caps and they visually looked ok and even tested good in circuit.
The startup and bulk caps where replaced in it some years ago.

I first desoldered all 1000uF 6.3v Taicon HD 8x16mm capacitors on the switch and tested them out of circuit and then it became obvious what the problem was:
Their ESR ranged from 0.11 > 0.98!
So I replaced them with Rubycon ZLJ 1000uF 10v 8x20mm caps (10000 hours lifetime!)

Next I checked the ADP-40VP PSU where the caps also had measured ok in circuit.
Not so out of circuit: The Ltec LZG 2200uF 10v 12.5x20mm ranged in ESR from 0.05 to 0.80 & the lone Ltec LZG 1500uF 10v 10x23mm measured 0.05.
They got replaced with Panasonic FR 2200uF 16v caps in matching dimensions and the lone 1500uF cap got replaced with a Samxon GT 1000uF 25v cap in matching dimensions.
I checked ripple before and after the recap and it was an improvement at idle.
Though with a load the ripple is around 80mV which is not so great... (Did not check the load ripple before the recap).

I can't really fault the original caps, the switch is 10 years old now and has been running pretty much 24/7, but with the new caps rated for 10000 hours I'd be surprised if they fail within my lifetime
I also saw when Googling this PSU that there exists a direct replacement from Artesyn: NLP40-7605J which RS, Farnell, Mouser and Digikey stocks.

[TechGeek]

Re: Dell PowerConnect 2716 and ADP-40VP PSU recap

Is it working now?

[momaka]

Re: Dell PowerConnect 2716 and ADP-40VP PSU recap

Nice job, Per!

That PSU should indeed last a very long time. The only thing I am concerned about is the heat/burn marks under the primary bulk cap. Does the PSU run hot, especially in that area? If yes, I wonder why only the primary side and nowhere else. SMD snubber network on the solder side, perhaps?

Is it working now?

I'm guessing so. If he was able to test it and all.

[diif]

Re: Dell PowerConnect 2716 and ADP-40VP PSU recap

I have an identical PSU in a Dell PowerConnect 2724.
It also has a heat mark in the same place, a bit worse.
The big primary cap on mine was visibly bulging, so i wonder if that would cause the resistor to heat up ?

[TechGeek]

Re: Dell PowerConnect 2716 and ADP-40VP PSU recap

Maybe. That capacitor may slowly be turning from a capacitor into a resistor into a virtual piece of 0-gauge wire bridged across the 2 capacitor terminals.

[Per Hansson]

Re: Dell PowerConnect 2716 and ADP-40VP PSU recap

momaka: Yea the heating on the primary side was caused by the primary capacitor failing, which is a very common failure mode in this PSU.
There even exists "rebuild kits" on eBay for it...

TechGeek: Heh, left that part out didn't I? Yea it's working fine after the recap
I was a little skeptical at first because I know from Linksys routers that when ports are lit randomly without a cable plugged in it's usually CPU damage...

diif: I think the failing bulk capacitor causes the diodes to work too hard with resulting overheating.

Edit: would have been nice to replace the two SMD caps as well but have no idea what their ratings are. (Anybody have some idea bar the obvious 16v 100uF?)
For sure they can't have had an easy life when all the other caps around failed...

[Per Hansson]

Re: Dell PowerConnect 2716 and ADP-40VP PSU recap

would have been nice to replace the two SMD caps as well but have no idea what their ratings are. (Anybody have some idea bar the obvious 16v 100uF?)
For sure they can't have had an easy life when all the other caps around failed...

Curiosity took the better of me:
Looking in the datasheet for the AMS1505 voltage regulator it seemed like the lower the ESR the better.
So I bought some with 0.45Ω ESR & 197mA ripple. (Elfa artno: 110-49-914)
They even have 2000h endurance at 125°C.
Switch seems happy enough with them

Anyway the old ones where the shocker:
Bop parker ESR meter does not see a cap at all.
My "component tester" says one has 200uF capacitance and the other 300uF.
The ESR is listed as 0.14K or 140!
And the leakage is at around 10%
Dear god, poor switch, how did it survive this abuse?!

[momaka]

Re: Dell PowerConnect 2716 and ADP-40VP PSU recap

Anyway the old ones where the shocker:
Bop parker ESR meter does not see a cap at all.
My "component tester" says one has 200uF capacitance and the other 300uF.
The ESR is listed as 0.14K or 140!
And the leakage is at around 10%
Dear god, poor switch, how did it survive this abuse?!

Nice work, Per!

Wow, those SMD caps for sure are dead. My component tester typically shows caps 0.15k for near open-circuit caps... with the occasional Sacon FZ being interpreted as a film/ceramic cap with just a few picoFarads of capacitance. And the truly open-circuit caps show as "no, unknown, or damaged component".

That said, it is indeed interesting how the switch managed to survive with those caps, considering they appear to be connected to a buck regulator. After all, we know what happens to those LinkSys WRT54G routers when they have really bad caps.

However, it seems that not all buck regulator circuits are intolerant of bad caps. Case-in-point, your switch. But I've also had a lot of XFX video cards with completely open-circuited Sacon FZ filter caps and both the RAM and GPU survived.

[katiekate]

Re: Dell PowerConnect 2716 and ADP-40VP PSU recap

Thank you everyone for the great advise on this thread. I was able to resurrect an old Netgear switch I bought used by replacing the C3 cap as suggested.

One strange thing on my board was that the cap was labeled C3 on the parts side, but C5 on the underside. Either way, it was a 47uF 25V which I replaced with a 35V equivalent, and now it works.

Kate

[nastysimon]

Re: Dell PowerConnect 2716 and ADP-40VP PSU recap

I have the same switch and replacing the 47uF 25V cap brought it back to life. Thanks for saving me the hassle and cost of getting a new switch.

[Per Hansson]

Re: Dell PowerConnect 2716 and ADP-40VP PSU recap

Welcome to Badcaps and congrats on the successful repair!
Might be worth reading this thread in full though incase some more caps are near failing like in mine...

[matszal]

Re: Dell PowerConnect 2716 and ADP-40VP PSU recap

Hi everyone. Big thank you for support and dedication. I was able to bring back to life my friends old netgear switch after replacing C3 capacitor. Thank you!

[qman777]

Re: Dell PowerConnect 2716 and ADP-40VP PSU recap

Ditto! Bought a couple of $0.10 caps to replace the C3 in two switches and brought them back to life! Saved two pieces of electronics from going to eWaste. Thanks!