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Short lived Electrolytic

 
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Short lived Electrolytic

Post by crackle » Wed Oct 07, 2015 4:19 pm

Are these the shortest lived capacitors?

Gill's digital photo frame packed up working this week after less than 2 years constant use. It was powered by a small 5v mains adaptor, which when tested was only giving about 2 volts.

When I cut the adaptor case apart (with a lot of effort using a Stanley knife) there were 2 caps that looked faulty with bulging tops. On removal these both definitely tested as faulty on my ESR meter.
cap1.jpg
cap 2.jpg
cap 2.jpg (35.21 KiB) Viewed 893 times


At first glance I thought the smaller cap which measured over 4 ohms ESR was mounted on a ferrite bead, I had thought to fit it over the leads of the replacement cap but for some reason I didn't bother.
Later, on closer inspection I found what I thought had been ferrite was in fact rubber. The aluminium can had been forced upwards exposing the rubber bung sealing the end of the cap.
Cap 2a.jpg


Mike

 
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Re: Short lived Electrolytic

Post by Cathovisor » Wed Oct 07, 2015 5:11 pm

'fraid so, Mike.

I've had set top boxes brought in to me in the past where the elkos have died within three years. We had a spate of computer motherboards in one of the TC studios where a block replacement was necessary within a couple of years - the computers were on 24/365 as they were part of the control system.

 
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Re: Short lived Electrolytic

Post by Refugee » Wed Oct 07, 2015 5:47 pm

Capacitors are not very reliable unless you buy them from a quality supplier.
Two or three years is about right for cheap capacitors.

 
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Re: Short lived Electrolytic

Post by sideband » Wed Oct 07, 2015 6:43 pm

Refugee wrote:Capacitors are not very reliable unless you buy them from a quality supplier.
Two or three years is about right for cheap capacitors.


That's not to say that your photo frame was cheap! Remember that all manufacturers want to maximise profits and will buy components from the cheapest supplier. Two years is about right for these minuscule capacitors in a hot environment, tightly packed against heatsinks and other hot components with (I'll bet) no ventilation slots.

 
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Re: Short lived Electrolytic

Post by Katie Bush » Wed Oct 07, 2015 8:41 pm

If it's of any comfort, I had 2 x 1800uf caps failed in the PSU of my CCTV recorder.. Replaced them about eighteen months ago - they stiffed out at barely a year's 24/7 use.

I have yet to replace them again, the point being that the CCTV caught the culprit, and the constabulary did the rest..... :aad :aak

Modern caps are a far cry from the 4oz ally cans of yesteryear... :elc:

Marion

 
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Re: Short lived Electrolytic

Post by Marconi_MPT4 » Wed Oct 07, 2015 9:18 pm

Even the better quality manufacturers can get it wrong from time to time and had to do a major recall on several product lines. It cost (50,000+ dud caps), but in the event it was discovered our particular brand had skipped the forming process in one of their HK factories.

As is often the case, just did a search for capacitor data which turned up blank. Says it all.

Pronounced in an 'Engrish' way, it certainly is. :qq1
Cheers
Rich

 
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Re: Short lived Electrolytic

Post by hamid_1 » Wed Oct 07, 2015 9:28 pm

It's not unusual for those switch mode power supplies to fail like that.

(A tip when trying to open a sealed mains adaptor, place it in a vice and squeeze it along the seam where the two halves of the plastic case are stuck together. It should crack open. After repairing it, superglue it back together again. I've repaired quite a lot of them, even though they are designed to be throwaway items.)

Bear in mind that if the power supply has been running for 2 years continuously, it will have accumulated more than 10,000 hours use. That could be the rated life of those capacitors in that situation. Switch mode power supplies are quite tough on electrolytic capacitors. There are pulses of high current, often thousands of times a second. The high current pulses can cause the capacitors to get hot, which decreases their life, and eventually they burst. Ideally, suitable low ESR capacitors should be chosen for switch mode power supplies, but as always, companies are tempted to cut costs and use the cheapest components. Also, the manufacturer of your digital photo frame may not have made the power supply to go with it. They probably bought it as a ready-made unit from another supplier, and again, probably the cheapest supplier. Even big-name companies like Apple have been caught out by buying power supplies and capacitors from cheap, low-quality sources. Just because you buy an expensive branded name product doesn't guarantee it will last longer.

On the plus side, I've been able to get hold of lots of newish broken electronic stuff very cheap or free, and fix it easily by replacing the burst capacitors. The same faulty switch mode power supplies are found inside almost all modern electronics like DVD players, digital TV set top boxes, DAB radios, LCD TVs and monitors. I used to get these from car boot sales (and from the dump before they stopped the public from buying electrical items), fix them and use them myself or sell them for a bit of extra money.


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