HIGH QUALITY, HARD TO GET AND CUSTOM ELECTROLYTIC CAPACITORS FOR POWER SUPPLIES, DISPLAYS, TVs, MOTHERBOARDS AND MORE!

Bad X capacitors?!

Hardware Insights specializes in power supplies. In this part of the forum, you will find detailed information on every aspect of power supplies, including how to repair them and how to judge if a power supply is a good quality unit or not.

Bad X capacitors?!

Postby LongRunner » May 5th, 2015, 9:26 am

Yes, they can fail too. See: http://www.vintage-radio.net/forum/show ... hp?t=59610

To my knowledge, besides self-healing events, internal corona discharge (which progressively eats away at the metallisation) is what eventually does them in. Of course, the only consequence of their failure in EMI filters is an increase in differential-mode interference, making their failure even more covert than typical age-related failures (dried-out electrolytics, etc.). It could be that you have a PSU (maybe several) with an X capacitor that has been practically open circuit for years, without knowing it.

Not having a capacitance meter of my own (yet) I can't personally attest to that experience, but it's something to take notice of. Could we knock points off units with low-quality X caps? There are endurance tests for X and Y caps, but it's not as though the makers of crappy 'lytics don't give endurance spec's.
Information is far more fragile than the HDDs it's stored on.

Smart people don't buy "smart" devices without very carefully weighing up the risks and benefits beforehand.

My PC: Core i3 4130 on GA-H87M-D3H with GT640 OC 2GiB and 2 * 8GiB Kingston HyperX 1600MHz, Kingston SA400S37120G, WD3003FZEX-00Z4SA0 and HDS721010CLA630, Pioneer BDR-209DBKS and Optiarc AD-7200S, Seasonic G-360, Chenbro PC31031, Linux Mint Cinnamon 20.2 (with Windows 7 still accessible if needed).
LongRunner
Moderator
 
Posts: 906
Joined: May 17th, 2013, 5:48 pm
Location: Albany, Western Australia

Re: Bad X capacitors?!

Postby Behemot » May 5th, 2015, 1:37 pm

This happenes for all film/foil caps. Misused foil caps even from Panny or Rubycon will fail. Besides I have no idea what manufacturer is good and what is bad, there are thousands of them. Many times you are not even able to identify.

As for safety caps, they are designed so they only loose their ability to act as capacitors, that means loose the capacity because of metal film evaporization. They should never short.

For measuring these caps you need very low capacity meter, ESR Micro is only able to measure the bigger ones from 0,1 uF.
User avatar
Behemot
Administrator
 
Posts: 408
Joined: November 28th, 2014, 8:57 am
Location: CZ

Re: Bad X capacitors?!

Postby LongRunner » May 5th, 2015, 11:16 pm

To straighten out the terminology: The capacitors in question are metallised film types. Film and foil caps are different – those have thicker aluminium foils, which provide lower ESR, but they are bulkier for the same capacitance/voltage and cannot self-heal. (As I understand the terms, "foil" conventionally refers to a thin sheet of a metal while "film" conventionally refers to a thin non-metallic sheet, most often plastic.)

Anyway, I know that it's an inevitability, more-or-less (although some manufacturers are claimed to be worse than others). For what it's worth, for dropper applications, there is a "high stability" variant with series instead of mono construction. The trade-off is that they are bulkier for the same capacitance and voltage rating.

If surges are the main problem, using X1 capacitors (designed for equipment for fixed installation) instead of X2 might help. (Strangely, Kemet seems to be under the impression that you can't use X1 caps in plug-in devices. :huh:) If it's corona discharge doing most of the damage, failure would be quicker at higher mains voltages (a given make and model of cap might be stable for years on 120V, but not for very long on 230V).

For the time being, I would suggest the "innocent until proven guilty" treatment, as far as scoring deduction goes.
Information is far more fragile than the HDDs it's stored on.

Smart people don't buy "smart" devices without very carefully weighing up the risks and benefits beforehand.

My PC: Core i3 4130 on GA-H87M-D3H with GT640 OC 2GiB and 2 * 8GiB Kingston HyperX 1600MHz, Kingston SA400S37120G, WD3003FZEX-00Z4SA0 and HDS721010CLA630, Pioneer BDR-209DBKS and Optiarc AD-7200S, Seasonic G-360, Chenbro PC31031, Linux Mint Cinnamon 20.2 (with Windows 7 still accessible if needed).
LongRunner
Moderator
 
Posts: 906
Joined: May 17th, 2013, 5:48 pm
Location: Albany, Western Australia

Another problem

Postby LongRunner » May 6th, 2015, 2:02 am

I found this article, which states that in recent times, manufacturers have reduced the thickness of the sealing compound and/or the casing (the article doesn't make it clear which); presumably in a desperate attempt to make capacitors just that bit more compact. Given the increase in moisture susceptibility that resulted, this turned out to be futile.

Until they develop a new dielectric with superior volumetric efficiency and HF performance comparable or superior to polypropylene, I think they'll have to stop there.
Last edited by LongRunner on June 9th, 2018, 7:24 am, edited 1 time in total.
Reason: Original URL died; repaired link to Wayback Machine
Information is far more fragile than the HDDs it's stored on.

Smart people don't buy "smart" devices without very carefully weighing up the risks and benefits beforehand.

My PC: Core i3 4130 on GA-H87M-D3H with GT640 OC 2GiB and 2 * 8GiB Kingston HyperX 1600MHz, Kingston SA400S37120G, WD3003FZEX-00Z4SA0 and HDS721010CLA630, Pioneer BDR-209DBKS and Optiarc AD-7200S, Seasonic G-360, Chenbro PC31031, Linux Mint Cinnamon 20.2 (with Windows 7 still accessible if needed).
LongRunner
Moderator
 
Posts: 906
Joined: May 17th, 2013, 5:48 pm
Location: Albany, Western Australia


Return to POWER SUPPLIES!

Who is online

Users browsing this forum: No registered users and 3 guests