Tantalum or Electrolytic for PSU?

Discussion in 'General Electronics Chat' started by Still Learning, Aug 11, 2010.

  1. Still Learning

    Thread Starter New Member

    Jul 19, 2010
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    Sourcing components for this PSU:

    http://www.qsl.net/yo5ofh/projects/vps/vps.htm

    It has been mentioned to use solid Tantalum caps for C1 + C3 at least, but would a Electrolytic cover it? The schematic also calls for C1 to be 2200uF @ 64V, but all I can source (so far) is a 2200uF 50V Electrolytic - should I be concerned of the voltage rating if I only use a 25VAC transformer?
     
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
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    50V will be fine, and ignore any references to tantalum caps. At one time they were praised due to tolerance, low ESR & stabiltity but with the modern common electrolyics being so good the tantalums have just fallen inrto a high $$ niche spot.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Tantalums tend to go off like firecrackers if left un-powered for an extended period of time.

    Use fresh electrolytic caps. You can help the response time if you parallel the large electrolytics with some much smaller low-ESR caps.
     
  4. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Another thing I keep forgetting to mention is that it's definitely worth the few extra pennies to buy 105*C electrolytics as opposed to the ones only rated for 85*C, the life at room temperature or not much above it can be anywhere from 5 - 20x as good.
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,766
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    While tantalums are better than average caps I have to agree with Wookie on this one. Never had one go off like firecrackers, more like match heads. More than one too. I remember working on a test fixture that had an intermittent noise problem with cold spray when one went up. It was in the middle of a board I would have to fix (no options) and I had the cold spray in my hands, so it made an impromptu fire extinguisher. Even with the cold spray continuously dousing it it still burned to the ground. These are not flame proof components.
     
  6. Still Learning

    Thread Starter New Member

    Jul 19, 2010
    25
    0
    Thanks,
    I've got a good assortment of Low ESR Caps, and I'll have a look for some 105deg ones too!

    Thanks guys
     
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