How to keep your SX270 caps alive

[Topcat]

I recently bought a shitload of off-lease Dell SX270 systems, all of which had bad caps in them. These little critters are prone to even roasting good caps, I see them all the time with bad Rubycon's and Panasonics in them. The reason is poor heat dissipation. Even good caps will fail if they overheat.

I noticed in this bunch of SX270's, there was a lowly little SX260, which uses the same case, just a different motherboard. It was full of Nichicon HN series caps, that miraculously haven't failed, the system still worked... I was scratching my head wondering why as I recapped it anyway... When I went to test it, I noticed something... The fans in the SX260 blow in reverse of the SX270. The SX260 blows downward, pulling in cool air from the top, through the system, then through the CPU heatsink, and then out of the case through the bottom. The SX270 pulls air in from the bottom, and then passes the already hot air over the northbridge (which makes it even hotter), then over a 5W resistor (which gets miserably hot), and then expels out the top of the case. See the image below:



This made me wonder what drugs the Dell engineers were on when they thought of this... The caps around the resistor are always the first to go, and there's no wonder why... The fix I came up with is insanely simple. Just reverse the fans in the cage, so the cool air is drawn from the top, pulled across the motherboard and CPU, and then expelled from the bottom.

The process for this is extremely easy. Just remove the side of the case, and unsnap the fan cage from the heatsink bracket. Carefully push the rubber fasteners outward, releasing the fan from the bracket.



You now want to grab the rubber fasteners from the base, and give them a tug, they'll pop right out of the fan.




You then want to simply turn the fans around and reinstall the rubber fasteners on the opposite side of the fan, reassembling everything reverse of how you took it apart.





When done, this is how the air will flow though the case:


After doing this, the resistor and caps around it are MUCH cooler. The CPU isn't running any warmer either, and I've abused the test system I initially tried this on, no glitches whatsoever. Those wanting to squeeze a few more years out of their SX270 may want to give this a shot, as it's proven itself very effective on several of mine.

[arneson]

Re: How to keep your SX270 caps alive

It's tips like this that make me think of an old Dylan song,
'The Answer is Blowin in the Wind'
With fans turned the wrong direction it's as if they wanted the system to fail early.
Does it also sound any different?

[sofTest]

Re: How to keep your SX270 caps alive

This made me wonder what drugs the Dell engineers were on when they thought of this...

I can only guess, but they probably thought it would be more effective to drive the natural flow of hot air; up. Inside a small constricted space like a cabinet, that would not be much of a problem to fight, as you have demonstrated. On a bigger scale, in a building, I've seen failed attempt to control natural airflow by zoning failing miserbly. I'm not familiar with those cabinets, but it sounds to me like there is a heat trap under the top, when the fans blows upward. The flaw you have demonstrated might not have appeared if the vents on the top had been better/bigger, releasing hot air faster. Just my 2 cent.

[dood]

Re: How to keep your SX270 caps alive

a very good thought sofTest. They were likely using the old "hot air rises" idea. At least they put fans in the thing and didn't just rely on convection, a la Mac.

[dood]

Re: How to keep your SX270 caps alive

Oh, and I just finished recapping a second one of these systems for a customer. I've sent him the link to this thread advising him to reverse the flow.

[Krankshaft]

Re: How to keep your SX270 caps alive

My brother has a Dell Dimension 4700 P4 with a similar fan setup but instead of two small fans he just had a larger one.

One day I was plugging in a flash drive into the USB port and felt hot air exiting through the front bezel this puzzled me and felt odd.

Upon going into the computer they had the proprietary (special connector ) CPU fan drawing air into the case accross the heatpipe heatsink and forcing it out the front.

Contrary to the power supply that was oriented in a normal fashion (pulling the hot air in the case out through the rear).

So I reversed the CPU fan by flipping it and I don't feel anymore hot air leaving the front now only cool air being drawn in. I'm sure now the case is much cooler inside.

Unfortunately though Speedfan can't find any temp sensors or voltage sensors on this cheap POS board so I couldn't monitor any before and after temp differences.

I remember when my bro bought this PC and it was cheaper then when I built mine from scratch.

I wondered how do they build these comps so cheap with a monitor no less I thought at the time quantity discount?

Now I know why they cut out little things here and there that lead to annoying problems later. Not to mention they manufacture cheap shoddy products just look at Dell's monitors blowing the C5707s left and right.

At least on my Intel manufactured board I have a slew of temperature and voltage sensors and STANDARD onboard fan plugs .

[Krankshaft]

Re: How to keep your SX270 caps alive

This made me wonder what drugs the Dell engineers were on when they thought of this...

They probably drank the bong water before work .

Speaking of which does anyone remember that pot smoker who used to be on their commercials?

Remember "Dude you're getting a Dell!".

If thats not foreshadowing of their quality I don't know what is.

Everytime my brother has problems with his Dell I say that it pisses him off so much .

[Newbie2]

Re: How to keep your SX270 caps alive

Probably DELL planned of putting planned obsolescence on their SX270 computers, since the caps in the SX270 kept failing in a few years. I guess DELL hoped to get more sales on new computers to replace the failed SX270 computers with bad capacitors that some businesses have.

[gdement]

Re: How to keep your SX270 caps alive

Probably DELL planned of putting planned obsolescence on their SX270 computers, since the caps in the SX270 kept failing in a few years. I guess DELL hoped to get more sales on new computers to replace the failed SX270 computers with bad capacitors that some businesses have.

I don't think planned obsolescence is necessary with computers. People regard them as obsolete for performance reasons before very long, and having them break down just ensures that the customer won't buy the same brand when they upgrade.