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I had some contact with PSU designers at a name brand server company and learned some things: 1. Electrolytic capacitors: Only Japanese brands can be trusted (

I had some contact with PSU designers at a name brand server company and learned some things: 1. Electrolytic capacitors: Only Japanese brands can be trusted (this sounds racist or something, but it's an actual requirement). They all should be de-rated for reliability (have 2x the voltage rating). Only exception is the main bulk filter capacitors, where your only reasonable choice is 450V, but these should be 105C. Tantalum capacitors: not allowed. 2. Main switch MOSFETs: only Infineon can be trusted. Single active clamp / single switch topology is a no-no due to bad experience. (I think the one in the article uses a diode clamp, so should be OK). 3. Standby supply needs its own fuse. The problem is that the main fuse is too big for the standby supply. If there is a standby supply fault, you will fill the machine room with smoke and your brand will be mentioned in the news when machine room is shut down. This destroys shareholder value. The current limit for any exposed 12V rail is only 20A or something line that (240VA UL limit), so you must not have exposed 12V when the server cover is open. There was basically a 100 page requirements document all along these lines.

indigomm 5y ago
Japanese brands are renowned for having a very reliable electrolyte formula. Dell sourced some capacitors made in Taiwan using a stolen copy of the formulae and it cost them massively. https://www.theguardian.com/technology/blog/2010/jun/29/dell-problems-capacitors https://www.theguardian.com/technology/blog/2010/jun/29/dell...
- goldcd 5y ago
  Wasn't just Dell - https://en.wikipedia.org/wiki/Capacitor_plague#:~:text=The%20capacitor%20plague%20was%20a,generation%2C%20often%20rupturing%20the%20case https://en.wikipedia.org/wiki/Capacitor_plague#:~:text=The%2... Although even putting this aside, capacitors don't seem to age well - anybody interested in 80s/90s electronics and gaming, will be aware that they should check boards before plugging them in, and if in doubt, but a 're-capping' kit
  - galangalalgol 5y ago
    An old school RF engineer told me you can put an incandescent light bulb in the enclosure for a few hours periodically to bake out the moisture and they are fine again. I was going to re-cap a 60s heathkit tube stereo and he asked me why I thought they had been fine for half a century but suddenly might blow any second? If you used the tube amps regularly the heat from the tubes kept the caps good.
    - zokier 5y ago
      That's... not how things work. Generally electrolytic capacitor lifetime halves for every 10°C temperature increase. Ref: http://www.rubycon.co.jp/en/products/alumi/pdf/life.pdf http://www.rubycon.co.jp/en/products/alumi/pdf/life.pdf https://www.digikey.dk/Web%20Export/Supplier%20Content/CDE_338/PDF/CDE_PredictingLifeTemp.pdf https://www.digikey.dk/Web%20Export/Supplier%20Content/CDE_3... https://jianghai-europe.com/wp-content/uploads/Jianghai-Europe-E-Cap-Lifetime-Estimation-long-AAL-2018-09-18.pdf https://jianghai-europe.com/wp-content/uploads/Jianghai-Euro... (page 9)
      - deleted 5y ago
        [deleted]
      - galangalalgol 5y ago
        Is it possible those old caps used something else? He said the electrolyte was hygroscopic.
        formerly_proven 5y ago
        Yes. Capacitors before around ~1990 used organic solvents and were, generally speaking, very reliable. Capacitors since then switched to water-based electrolytes, which are 1) much more aggressive which 2) leads to circuit board damage if they leak and 3) if done improperly has very bad longevity. Capacitor plague is basically all of these downsides combined in one sweet package: capacitors that fail quickly, and do so while leaking acid all over your circuit boards, acid which is strong enough to eat through solder resist, copper, fiberglass and even goes into IC packages, damaging them invisibly. Old-timey capacitors with organic electrolytes are still available for applications that need reliability more than the best ESR or highest density, but they're kinda rare and expensive.
geocrasher 5y ago
I can't tell you how many computers I replaced the mainboard for because of blown capacitors. Or the number of monitors I re-capped and brought back to life. It's a known thing in the LCD TV industry as well. Some industrial espionage went wrong and a bad electrolyte formula was stolen, and of that's of course what manufacturers who were trying to save a buck (all of them for the most part) got. Source: https://en.wikipedia.org/wiki/Capacitor_plague https://en.wikipedia.org/wiki/Capacitor_plague
kwdc 5y ago
Can't speak for the other aspects, but the capacitors issue was/is definitely a real thing. I know plenty of techs who spent weeks removing equipment due to faulty capacitors. Some of that equipment was worth having component swaps performed others were just junked / returned etc. Nothing like "we're spending this whole month dealing with bulging or otherwise faulty capacitors" to raise eyebrows. As I recall it was a rolling wave of work done to mitigate multiple supply chain failures. "Just" because of capacitors.

indigomm 5y ago

Japanese brands are renowned for having a very reliable electrolyte formula. Dell sourced some capacitors made in Taiwan using a stolen copy of the formulae and it cost them massively. https://www.theguardian.com/technology/blog/2010/jun/29/dell-problems-capacitors https://www.theguardian.com/technology/blog/2010/jun/29/dell...

goldcd 5y ago
Wasn't just Dell - https://en.wikipedia.org/wiki/Capacitor_plague#:~:text=The%20capacitor%20plague%20was%20a,generation%2C%20often%20rupturing%20the%20case https://en.wikipedia.org/wiki/Capacitor_plague#:~:text=The%2... Although even putting this aside, capacitors don't seem to age well - anybody interested in 80s/90s electronics and gaming, will be aware that they should check boards before plugging them in, and if in doubt, but a 're-capping' kit
- galangalalgol 5y ago
  An old school RF engineer told me you can put an incandescent light bulb in the enclosure for a few hours periodically to bake out the moisture and they are fine again. I was going to re-cap a 60s heathkit tube stereo and he asked me why I thought they had been fine for half a century but suddenly might blow any second? If you used the tube amps regularly the heat from the tubes kept the caps good.
  - zokier 5y ago
    That's... not how things work. Generally electrolytic capacitor lifetime halves for every 10°C temperature increase. Ref: http://www.rubycon.co.jp/en/products/alumi/pdf/life.pdf http://www.rubycon.co.jp/en/products/alumi/pdf/life.pdf https://www.digikey.dk/Web%20Export/Supplier%20Content/CDE_338/PDF/CDE_PredictingLifeTemp.pdf https://www.digikey.dk/Web%20Export/Supplier%20Content/CDE_3... https://jianghai-europe.com/wp-content/uploads/Jianghai-Europe-E-Cap-Lifetime-Estimation-long-AAL-2018-09-18.pdf https://jianghai-europe.com/wp-content/uploads/Jianghai-Euro... (page 9)
    - deleted 5y ago
      [deleted]
    - galangalalgol 5y ago
      Is it possible those old caps used something else? He said the electrolyte was hygroscopic.
      - formerly_proven 5y ago
        Yes. Capacitors before around ~1990 used organic solvents and were, generally speaking, very reliable. Capacitors since then switched to water-based electrolytes, which are 1) much more aggressive which 2) leads to circuit board damage if they leak and 3) if done improperly has very bad longevity. Capacitor plague is basically all of these downsides combined in one sweet package: capacitors that fail quickly, and do so while leaking acid all over your circuit boards, acid which is strong enough to eat through solder resist, copper, fiberglass and even goes into IC packages, damaging them invisibly. Old-timey capacitors with organic electrolytes are still available for applications that need reliability more than the best ESR or highest density, but they're kinda rare and expensive.

geocrasher 5y ago

I can't tell you how many computers I replaced the mainboard for because of blown capacitors. Or the number of monitors I re-capped and brought back to life. It's a known thing in the LCD TV industry as well. Some industrial espionage went wrong and a bad electrolyte formula was stolen, and of that's of course what manufacturers who were trying to save a buck (all of them for the most part) got. Source: https://en.wikipedia.org/wiki/Capacitor_plague https://en.wikipedia.org/wiki/Capacitor_plague

kwdc 5y ago

Can't speak for the other aspects, but the capacitors issue was/is definitely a real thing. I know plenty of techs who spent weeks removing equipment due to faulty capacitors. Some of that equipment was worth having component swaps performed others were just junked / returned etc. Nothing like "we're spending this whole month dealing with bulging or otherwise faulty capacitors" to raise eyebrows. As I recall it was a rolling wave of work done to mitigate multiple supply chain failures. "Just" because of capacitors.