Antec Aria AR300 PSU Repair

Page 3 of 17:

Top Side

Since the top usually hosts a majority of the components we might be interested in, let's start there. Given how the two heat sinks cover nearly everything of interest, I decided to go with an angled shot. Most of the 5VSB and auxiliary components, the main points of interest, are along the board's front edge anyway.

Hidden under the primary side heat sink on the right, there is a substantial pileup of EMI filtering components, one input filter inductor, a chunky toroidal inductor for active power factor correction, the APFC and main converter MOSFETs in TO-247 packages, the APFC diode in TO-220 packaging and the 400V 220µF Fuhjyyu main input cap poking out in the top-right corner.

On the primary side of the 5VSB/auxiliary transformer, we find a 50V 100µF capacitor that appears to be the main auxiliary output filter cap, a 50V 22µF cap next to it that's presumably part of the primary side's feedback loop based on its proximity to the photocoupler, along with a handful of diodes and resistors.

The secondary side offers little worth noting. Aside from the usual crop of output filter inductors and rectifiers, we do have the following list of visibly strained capacitors:

a weepy 10V 4700µF Fuhjyyu TMR on the 3.3V rail – the tall blue one on the left
a pair of slightly bulged 10V 2200µF Teapo SEK for the main 5V output hidden under the heat sink, one of them partially visible just above the TMR capacitor with a blob of brown-orange adhesive on top of it
a pair of 10V 1000µF Teapo SEK for the 5VSB output near the bottom edge

Does anything else stand out on the top side? Yes, there is one fairly clear sign of something gone wrong if you look closely enough.

While looking around for capacitors that show an obvious need for replacement or other obvious issues, I noticed a discolored area around the diode next to the 5VSB transformer labeled ZD4. The device in question is a 1N4746, a 18V 1W zener diode. Does it get that hot by design? Did it get that hot due to a failure elsewhere? Did it fail? I powered up the unit for a few minutes, turned it off and felt around but could not find anything that appeared to warm up significantly apart from the 5VSB dummy-load resistor, which was getting scalding hot from having four times the power it is supposed to draw going through it due to the 5VSB rail rising to twice what it should be. This is one of those situations where a thermal imaging camera would come in really handy: watching the whole board warm up in real time makes finding unexpected hot spots orders of magnitude faster, safer and easier.

Considering how hot a printed circuit board must get before it starts darkening like this, everything in the vicinity becomes a likely suspect. Even the printed circuit board itself might be in question if the charring got bad enough to start conducting enough to interfere with normal circuit operation.

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15 Comments Comment from the forums

iam2thecrowe

That was a good read. I have a lot of custom power supplies (not PC atx) that i would like to fix at work instead of replace, would be a lot cheaper (there's some high wattage power supplies that cost $5000 to replace). Need to convince the boss to buy a good oscilloscope.
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Rookie_MIB

I have several of those cases - they make nice little machines for office use but the PSUs tend to flake. I've had to replace several...
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Daniel Sauvageau

All the standby power supplies I remember looking at are of the good old flyback design and one particularity of the flyback topology is that it has the worst ripple current on the output capacitors of all converter topologies or in other words: it is the harshest on output capacitors. Until I saw the waveforms while poking around the SL300, one little yet important detail skipped my mind: the harsh current waveform behavior applies to ALL outputs.

Any flyback supply with sub-par output capacitors on any of its outputs will inevitably fail in relatively short order.

After that 'oops' moment, I decided to pop the lid on my LG 204WT which I thought had dying CCFL tubes, popped three of its auxiliary supply capacitors off the board, measured them at 5-20 ohms of ESR, replaced them, no more flicker or random turn-on issues.
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gnyff

I love it when stuff is repaired! It's so sad that almost every consumer device today is made to fail and be replaced. Even in the cases where the designer did not specifically design for failure most commonly it's definitely not cost-effective for the user to have it repaired. :-(

Anyways, I've also replaced one of those lousy non-standard PSU. Hard to find and depressingly expensive. Thus, I am avoiding non-standard parts as much as possible now! ;-)
By the way, in one of my systems the standby power was around 12W (!) even after shutting off 5VSB functions (wake on LAN, keyboard etc) in the BIOS. I did on bother to investigate further (thinking "lousy supply"!) and simply added a proper "full off" power switch. Probably other owners should think of doing the same ;-)
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Rookie_MIB

16509494 said:
Anyways, I've also replaced one of those lousy non-standard PSU. Hard to find and depressingly expensive. Thus, I am avoiding non-standard parts as much as possible now! ;-)
By the way, in one of my systems the standby power was around 12W (!) even after shutting off 5VSB functions (wake on LAN, keyboard etc) in the BIOS. I did on bother to investigate further (thinking "lousy supply"!) and simply added a proper "full off" power switch. Probably other owners should think of doing the same ;-)

I wonder if a SFX PSU could be mounted in those cases. Might be a viable solution...
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nukemaster

Another great one!

I actually was interested in that case back when it was released, but just kept rocking the Sonata and Sonata II. While my power supplies did not fail. caps leaked after a while(power supplies still worked)and I took the power supplies out of service forever.

Rookie_MIB,
SFX would be an interesting idea to see for sure. My SFX is still going after 5 years of 24/7 operation(not bad for a case included 300 watt unit).
Reply
Daniel Sauvageau

16509868 said:
I wonder if a SFX PSU could be mounted in those cases. Might be a viable solution...
The dimensions might fit but mounting holes would be on the wrong side (for mounting in a way that might fit internally) and the IEC socket would face either the motherboard or the top cover. Nothing some drill-and-tapping with some wire splicing cannot fix for people who would favor this route instead of a repair of the existing unit where that is possible.

BTW, the total repair cost for the 5VSB side is about $1.50 for the caps and resistor. The rest is basically free since I scavenged the SCs from a dead (catastrophic primary-side failure) PSU and would have cost around $2.50 otherwise. If Asus had specified higher quality parts from Channel Well though, the PSU may have cost less than $0.50 extra to get right on the first try. Evem doing as little as specifying Teapo SC as the minimum requirement would have easily doubled the trouble-free service life over using SEK..

It always bugs me when only a few pennies worth in parts and materials can spell the difference between a product that might only last 2-3 years and a product that should easily last 10+ years.
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nukemaster

That small cost per unit adds up.

I can not count the number of times I say, gee a xx cent part would have solved this damn issue and yet no one does it.

Drilling and making it fit is no issue. :)

I still get my small system fix with an SG05 case.

Where do you get your parts from? Digikey is not too expensive, but many times the shipping cost more than the parts(especially with resistors that are cheap to begin with.).
Reply
Daniel Sauvageau

16511613 said:
That small cost per unit adds up.

Where do you get your parts from? Digikey is not too expensive, but many times the shipping cost more than the parts(especially with resistors that are cheap to begin with.).
The "small cost" may add up but if you charge $1 to put the $0.50 worth of better quality parts in, you still make a 100% profit on that extra cost and you score points in the quality/reliability column. For the most part, those better quality parts are the same physical size, so no fitting or PCB layout concerns there.

As for where I get my parts, they are mostly Digikey. I either lump my order with parts I need to repair something for someone else (and pass the shipping cost to them) or build my order for multiple non-urgent projects until it qualifies for free shipping.

Edit: and for things like 0805 resistors and capacitors, I usually order in cut-tapes of 100 since we're still only talking $1-2 there. If I had more storage space, I would order whole reels for $10-15 (2000-3000 units) and likely never have to worry about ordering more of that resistor or capacitor value (for personal use) for the rest of my life.
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pjmelect

I often repair computer power supplies and I enjoyed reading this article. One comment, that may help others and may explain some things in the article such as the power reduction of the fixed power supply.
Capacitors with high ESR always have a very high leakage current near their rated voltage. The leakage current at low multi-meter voltage levels is not normally measurable, but increasing the voltage across the capacitor dramatically increases the leakage. Circuits with capacitors with high ESR in them normally fail not due to the ESR or the reduction of capacitance, but due to the high leakage current. If you do not have a ESR meter you can simply put a suspect capacitor across a power supply at its rated voltage and check the leakage current. A high leakage current is a good indication of a high ESR value.
I use a in-circuit ESR meter to test all of the electrolytic capacitors (even the small ones) before I even start trying to fault find a power supply.
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