When Doves Cry

Rubycon

Madame President
Aug 10, 2005
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Server power supply fault light glowing with alarm sounding. :Q

It's OK as there are three 300W modules and it can run even on 1 in a pinch so it's down to 2. :)

The nameplate for sake of familiarity:

Text

Some inside pics:

wide angle shot

cute little fan and quite the powerhouse at the expense of some noise :)

Backside of the mainboard - lots of components onboard!

Big toroids!

More toroid action!

Iron core transformer

Heatsink mounted MOSFETs with another toroid

control board

caps beneath the power heatsinks

The culprit - BAD CAPS! :| Look at the domed tops. :(

This IS (or was) a good power supply module. But failures can/do/will happen hence the need for redundancy when availability is important. It's not a matter of if it will happen but when. This supply is about 3 years old and has been in use 24/7 right up to failure a few weeks ago. In our biz we use the term "ship happens". That's why we keep spares onhand. :)
 

MarcVenice

Moderator Emeritus <br>
Apr 2, 2007
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so the 'domed' tops mean they've burst or something ?

Mind me asking some questions ? What are mosfets ? And are servers really that different then personal desktops? I'm guessing everything revolves around stability, but what else is different? And are there 3 psu's in 1 single case/mount, and when 1 goes down the second one will simply take over ?
 

JEDIYoda

Lifer
Jul 13, 2005
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Originally posted by: MarcVenice
so the 'domed' tops mean they've burst or something ?

Mind me asking some questions ? What are mosfets ? And are servers really that different then personal desktops? I'm guessing everything revolves around stability, but what else is different? And are there 3 psu's in 1 single case/mount, and when 1 goes down the second one will simply take over ?

all good questions...

I also would like to know from somebody who has on hands experience as opposed to somebody who maybe knows....

Waiting for your answers Rubycon :)

Thank You!! ahead of time...
 

Mark R

Diamond Member
Oct 9, 1999
8,513
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Originally posted by: MarcVenice
so the 'domed' tops mean they've burst or something ?

Mind me asking some questions ? What are mosfets ? And are servers really that different then personal desktops? I'm guessing everything revolves around stability, but what else is different? And are there 3 psu's in 1 single case/mount, and when 1 goes down the second one will simply take over ?

The domed tops mean that gas (usually hydrogen) has formed inside the capacitors because of some form of malfunction (damage, manufacturing fault, excessive stress or temperature) - it's often a symptom of the capacitor malfunctioning rather than the cause.

MOSFETs are a type of transistor, an electronic switch, capable of switching large amounts of power on and off hundreds of thousands of times per second. They are used to make 'switching' power supply units, which are a technology that allows high efficiency, light and compact power supply units to be made. The advantages of switching power technology means it is now the foremost technology for making PSUs for computers, cell phones, TVs and pretty much any other electronic device you care to name.

In servers, reliability is key. Equipment is designed so that it can be swapped out 'hot' while the server is still running, with no need for reboot. In just the same way as servers have 'hot-swappable' redundant hard drives (in the interim, the spare copy of the data on the other hard drives keeps the server running, until the replacement is installed and running), you can get hot-swappable PSUs. Under normal conditions, the PSUs share the load. If one malfunctions, or loses mains power, then the load will end up shared over the other PSU(s), meanwhile the faulty PSU can be swapped out with a replacement. For even higher reliability, the individual PSUs can be connected to separate UPSs or separate power circuits.



 

Mark R

Diamond Member
Oct 9, 1999
8,513
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81
Yup - certainly a lot of stuff packed into there.

Looks like a standard aPFC front end - RFI filter chokes on the right, NTC thermistor in the middle and aPFC storage inductor on the left.

Iron? Soft, high permeability ferrite hopefully. I'm not sure that even iron powder is a good idea for SMPS transformers.

Fairly standard 3.3V post regulator running off 5V. Nice big output filter inductor there.

Unusual to see lots of LM324s and LM339s these days. Still, they're old workhorses. You don't normally see such extensive analog circuitry in a typical home PC PSU - I guess that some of it is involved with the redundancy, protection and care in ensuring good regulation and stability.


Yup - bulging caps - never a good sign. Looks like the input reservoir caps too, I'm surprised they didn't pop.

 

Rubycon

Madame President
Aug 10, 2005
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The redundant module allows load splitting between power supply units. It does not, however mean you can get 900W out of it! The power supply is rated at 600W continuous. When a supply goes offline it will send an alert to the hardware sentinel, which is just a watchdog to alert the user that this particular box needs attention. Much in the way when a disk fails in a RAID array.

This particular supply features over temperature monitoring and alerting and the logs do not show any anomalous condition.

Server equipment is built around availability. Comfort is not really a factor with this type of equipment so it tends to run much louder than a desktop PC equivalent.

MOSFET = Metal Oxide Field Effect Transistor

plain English explanation here

Iron core transformer
Iron? Soft, high permeability ferrite hopefully. I'm not sure that even iron powder is a good idea for SMPS transformers.

I'm still waiting for the OK to pull it down further. Probably is a ferrite though. Good catch. :)