What Cap size fails most often?

[Bishop]

Last night after watching a car race everything on the Dish Network box was working fine. Before I could turn the Sat box on this morning we lost power for about 5 seconds.
Everything seemed OK until I turned the Sat box on to watch another car race, but the sat box was dead.
I pulled the box and took the motherboard out and found a Jamicon 25v 100uf cap had buldged, I guess during the blackout.
I had spare Rubycons so I replaced the bad Jamicon cap, and the Sat box is working again and Sundays race is on right now.

It made me wonder two things.

Is there a brand that fails most often, and is there a Cap size that fails more often than others?

[Bishop]

Re: What Cap size fails most often?

And is there a brand and size you keep in stock most often?

[Mint Waxed]

Re: What Cap size fails most often?

Last night after watching a car race everything on the Dish Network box was working fine. Before I could turn the Sat box on this morning we lost power for about 5 seconds.
Everything seemed OK until I turned the Sat box on to watch another car race, but the sat box was dead.
I pulled the box and took the motherboard out and found a Jamicon 25v 100uf cap had buldged, I guess during the blackout.
I had spare Rubycons so I replaced the bad Jamicon cap, and the Sat box is working again and Sundays race is on right now.

It made me wonder two things.

Is there a brand that fails most often, and is there a Cap size that fails more often than others?

The Japanese have the best reputation for quality control even though many are manufactured in low wage countries on their behalf. By nature of their construction and materials used, all electrolytic types are prone to failure. A lot depends on quality control during the manufacturing process and the operating conditions of the equipment. That's why most everyone who has been involved in the electronics hobby or repair prefer units rated at 105C. Also capacitor types designed for high temperature are available such as the Panasonic FC series. As for bulging, it has probably been slowly building pressure for quite a length of time. In my opinion, it was not actually caused by your power glitch. That issue would be best addressed by using spike protected outlet strips or if you can justify the cost, a UPS also known as APC for backup power.

[R_J]

Re: What Cap size fails most often?

Had you opened the sat box before the power bump you would have seen the same buldged cap. It was on its way out for some time but as long as there is constant power to the circuit it will usually stay running, once power is removed the power supply won't start up properly. Thats why people always blame the power companies for the failure but its usually not there fault, the same thing would have happened if you unpluged the box and pluged it back in again.

[Pentium4]

Re: What Cap size fails most often?

Seems like D8mm caps...because they're usually the smallest sized filtering caps. The ones smaller aren't in as critical of areas and the ones that are 10mm or bigger are large enough to be able to absorb or handle heat better.

[ChaosLegionnaire]

Re: What Cap size fails most often?

not really. an example are those D10mm 3300uF kzg caps which are also the worst offenders at leaking/bulging. probably something to do with too much water being contained in those large can size caps.

[Pentium4]

Re: What Cap size fails most often?

Well, KZG can't be saved by any scenario, I thought that was implied

[Wester547]

Re: What Cap size fails most often?

Jamicon doesn't fare well with heat as this thread markedly exemplifies.

not really. an example are those D10mm 3300uF kzg caps which are also the worst offenders at leaking/bulging. probably something to do with too much water being contained in those large can size caps.

Nope. Well, higher water content does reduce the boiling point of the electrolyte, but if KZGs lacked the necessary corrosion inhibitors to combat the aggressive H2O base electrolyte, then KZE would have issues too. Not of the same magnitude, but issues nevertheless (KZG is high in water content, KZE medium). Yet it takes a LOT of heat to make a KZE bulge and it's rare for that series to fail. And I would argue that the ratio of KZGs and KZJs that do and don't bulge is very random. Although I do wonder if the faulty run of HMs and HNs had that issue because much more so than KZG and KZJ, they are notorious for failing with very high capacitance readings and high leakage current (high vloss), which either means the aluminum oxide has dissolved into the electrolyte, the electrolyte has broken down and can't provide enough oxygen to correct defects in the oxide film, or the water-base electrolyte is attacking the aluminum oxide and will eventually cause foil corrosion because of missing or insufficient additives and compounds.

It all depends on how stable the electrolyte is. Exceptionally stable electrolyte won't need many depolarizers, hydrogen absorbers, and special additives to reduce the likelihood of failure. Heat does accelerate all chemical reactions, but that's all it does. It is an expeditor of a chemical reaction (the gradual build up of pressure and outgassing as the result of unstable chemistry AKA bad electrolyte, but impurities in the native oxide barrier and porous oxide film can slowly cause it too) that will eventually occur anyway. 8mm capacitors do have less surface area to dissipate heat, thinner dielectrics, and lower ripple ratings, which means that the cathode foil will oxidize (or be formed with a reverse voltage) at a lower current, and that familiar pressure and hydrogen gas we all love will follow. This is why it's a bad idea to use 8mm capacitors from less than esteemed brands on the output of the standby flyback converter in PSUs. (oh Teapo, where art thou? ) Or in Dish Network boxes...