Electronics > Beginners
CAPACITOR Checking
Siwastaja:
--- Quote from: Jwillis on July 26, 2019, 11:50:45 pm ---It's not unusual for electrolytic capacitors to go bad after 2 -3 years without reforming . Its depends on the manufacturer.For example Nichicon recommends no more than 2 years at 35C before forming is required.
--- End quote ---
This means they can't guarantee they are within specs, including leakage spec.
It doesn't mean the caps are "bad". They just need reforming to be in spec again. Reforming happens in-situ, when power is applied.
In practice, it means the leakage current is slightly more than specified for a few minutes to hours.
For example, it's completely normal that an assembled unit sits for 2-3 years before power is applied for the first time. You would have a huge epidemic of warranty issues if this timeframe was a problem.
If an elcap has gone bad enough to cause any issue (like excessive enough leakage current at first powerup to cause damage), after just 3 years, it's complete and total crap. No modern Nichicon or Panasonic cap does that.
Never seen that.
OTOH, in 30 (not 3) years old units, the result varies. Most of the time, they are fine, but the risk of caps blowing up or being severely out-of-spec (capacity and ESR), even after in-situ reforming, is considerable and varies a lot depending on manufacturers.
Siwastaja:
--- Quote from: vinlove on July 27, 2019, 08:05:14 am ---Both of newly found caps were near the value of 100uF. This is strange, because these newly found ones are actually a lot older from the manufacturer. They are actually almost 10-20 years old, but never been used. ESR was about 1.9 ohms.
--- End quote ---
Not strange at all - usually "almost 10-20 years old" elcaps are just fine as is, and measure fine. (Although they may show higher leakage current when voltage is first applied.)
The one that failed for you didn't fail because of time, but because it was crap from the beginning.
HighVoltage:
I got bags of electrolytics, all brand new, all originally packed, from a friend who closed a professional repair shop.
By looking at them, I could already see that some of them had leaked badly. I ended up testing all of them and more than 80% were deteriorated, although the brand was not bad.
Shock:
--- Quote from: vinlove on July 27, 2019, 08:05:14 am ---I have searched my component draws, and found a couple of Electrolytic capacitors of the same value = 100uF, but the one gone bad is rated at 16V. The newly found ones are rated at 10V.
Both of newly found caps were near the value of 100uF. This is strange, because these newly found ones are actually a lot older from the manufacturer. They are actually almost 10-20 years old, but never been used. ESR was about 1.9 ohms.
--- End quote ---
No component is impervious to being defective, even it if it brand new. Sometimes it's a bad batch or series, unless it's a quality brand really you shouldn't dwell on it too much. Just buy from a reputable source and stick to superior brands if you want reliable components.
Big difference with a marginal electrolytic capacitor and a bad one, don't waste time on dead ones. If you want to heal marginal caps, you can google reforming capacitors which should improve the capacitor you will need to monitor the ESR or leakage. Once done it will settle back after a period of time elapses if left out of circuit, it's one of those how long is a piece of string things. Not worth it for cheap capacitors.
Electro Detective:
If you haven't sledged it yet :horse:
Charge it up to it's operating voltage and discharge, repeat a few times,
then discharge it and run the tests again
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version