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Old/aging PSUs and reliability: is it just capacitors?

Discussion in 'Power Supplies' started by LuckyBenski, Dec 7, 2018.

  1. LuckyBenski

    Wise Guy

    Joined: Dec 28, 2017

    Posts: 1,633

    Location: London

    So I often turn down older PSUs when shopping for second hand parts. I'm generally of the received opinion that older PSUs are more likely to fail and also tend to lose capacity as they age.

    Is this just the capacitors aging or is it down to everything, the silicon, thermal cycles etc?

    I'm an electronic engineer so more than happy to replace parts if it's down to specific identifiable parts. I'm all for proper maintenance and making things last longer!
     
  2. Acme

    Caporegime

    Joined: Jul 29, 2011

    Posts: 28,434

    Location: Acme's chair

    I've had and used old old psu's before. 10 years old plus. I've used them at their rated power and had no issues.
     
  3. Rroff

    Man of Honour

    Joined: Oct 13, 2006

    Posts: 58,320

    Capacitors are the main one - though there are some resources out there where they do tear downs and you can see the types of capacitors used - a few years back far too many were using cheap far eastern junk caps that 10 years was good going - there are some that use decent Japanese capacitors, etc. where that is far less of a worry.
     
  4. EsaT

    Mobster

    Joined: Jun 6, 2008

    Posts: 4,481

    Location: Finland

    Of course pretty much everything wears at some rate in use.
    But good PSU built from quality components would have lot better reliability expectation even after five years of use than cheap junk fresh from factory.
    (at least if kept in normal environment and without having been filled with dust)

    And capacitors play pretty much the biggest part in that endurance.
    Just like in monitors and TVs.
    Power supply of backlight would usually fail lot before backlight itself thanks to cheap capacitors.
    Underhand Tactics: Planned Obsolescence documentary actually touched that.
    Showing some fine Samsung engineering using C(r)apXons next to semiconductor heatsinks to literally work as timer.
     
  5. tamzzy

    Soldato

    Joined: May 26, 2012

    Posts: 6,426

  6. EsaT

    Mobster

    Joined: Jun 6, 2008

    Posts: 4,481

    Location: Finland

    And from the original review:

    The use of Matsushita (Panasonic)capacitors on the primary side was welcome but there are some points of concern with the build. The secondary is going to suffer from restricted airflow with the design employed in the Olympia 1000w and the secondary is jam packed with CapXon capacitors.

    Cheap CrapXon caps without airflow to keep them cool.
    So what a surprise that ripple supression belly flopped.

    Either higher quality caps, or more airflow for them would have helped to maintain ripple supression...
    Preferably both.
     
  7. LuckyBenski

    Wise Guy

    Joined: Dec 28, 2017

    Posts: 1,633

    Location: London

  8. EsaT

    Mobster

    Joined: Jun 6, 2008

    Posts: 4,481

    Location: Finland