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SOX 135W series capacitor 50% out of spec.

SOX 135W series capacitor 50% out of spec.

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Recently got an ignitor ballast (Philips BSX135 H96) but found it wouldn’t run a lamp correctly. The lamp flickered continually and when the ignitor was removed it would extinguish. When checking each component, the series capacitor read half of its stated value. This was the issue. Dismantling the capacitor shows plate area is missing on both sides of the dielectric. The shading in the picture shows the aluminium coating on both sides of the dielectric. The missing plate area is easy to see and is not uniform throughout the capacitor. The darkest area is where the plates actually overlap on both sides of the dielectric forming the capacitor. There are no visible punctures in the dielectric. The capacitor rating is of the specified voltage and capacitance.

SOX_Sint.jpg plasma_globe.jpg Cap_plates.jpg anti-light.jpg

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Filename:Cap_plates.jpg
Album name:tuopeek / misc
Keywords:Miscellaneous
File Size:111 KB
Date added:Nov 25, 2018
Dimensions:1500 x 929 pixels
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Date Time:2018:11:25 17:35:21
DateTime Original:2018:11:25 17:28:32
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FNumber:f 5.6
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Focal length:36 mm
ISO:400
Make:NIKON CORPORATION
Model:NIKON D3400
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rjluna2
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Robert


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Nov 25, 2018 at 03:01 PM Author: rjluna2
Could this be due to the age of the capacitor?

Pretty, please no more Chinese failure.

tuopeek
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Tuopeek-475652085781113 tuopeek1 77334065@N05/
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Nov 25, 2018 at 03:13 PM Author: tuopeek
Robert, looks like just 4 years old and no signs of external damage.
dor123
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Nov 26, 2018 at 12:15 AM Author: dor123
Capacitors degrades in capacity during life, so if they ends their life in this manner, no visible damage will be seen. External damage will occur only if the case of an internal failure.

I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.

I only working with the European date format (dd.mm.yyyy).

I lives in Israel, which is a 230-240V, 50hz country.

Medved
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Nov 26, 2018 at 03:29 AM Author: Medved
The degradation is exactly what you see on the film from the capacitor: The dielectric breaks down here and there occasionally, activates the defect isolation mechanism (either evaporating the metal film around the defect, or a little fuse disconnecting the affected segment, method depends on the exact technology) and the capacitance what the disconnected area had becomes lost.
The breakdown happen due to either random overvoltage spikes and/or because of the TDDB mechanism (a charge becomes trapped, which then forms a bridge to make other charges to become trapped as well, gradually speeding that up till a chain completes shorting both electrodes; this mechanism is strong when the dielectric is highly loaded and accelerated by high temperature). In most cases both mechanisms are combined (spike kills the spot which already became weaker due to the TDDB). Because these effects are rather normal for the capacitor life, the recovery mechanism is an essential must, sometimes used on both electrodes, to ensure safety (on capacitors rated for direct mains connections without fuse).

No more selfballasted c***

dor123
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Nov 26, 2018 at 03:45 AM Author: dor123
A picture of a dead capacitor that lost most of its capacitance and have no external visible damage.

I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.

I only working with the European date format (dd.mm.yyyy).

I lives in Israel, which is a 230-240V, 50hz country.

tuopeek
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Tuopeek-475652085781113 tuopeek1 77334065@N05/
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Nov 26, 2018 at 01:14 PM Author: tuopeek
Your description explains the isolated rectangular construction of the plates. Each plate on both sides is connected to one end or the other. The small lead in track from the edge forms the safety fuse. If a catastrophic dielectric fail occurs only one section blows out the thin track.

I wondered if the ignitor could cause the capacitor damage if the lamp was missing or open circuit. The ignitor says “self-stopping”, but if the lamp is missing it reduces the pulse energy quickly but continues to produce small pulses. The peak pulse voltage is stated as 1.4kV so perhaps this could do the damage. Applying a high voltage to a small piece of the capacitor I found it started to breakdown at 2kV. This type of breakdown did remove the plate coating but leaves a “tree - like” breakdown pattern in the foil rather than pattern of dissolved plate as shown. However, no holes in the dielectric were observed so that would tie in with what has been seen. I don’t recommend this type of testing as parts of the plate can become isolated and remain charged after a discharge attempt. These tend to find a route home when handling the foil. Ouch!
rjluna2
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Robert


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Nov 27, 2018 at 06:36 AM Author: rjluna2
Indeed, Mark. Ouch

Pretty, please no more Chinese failure.

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