44 year old electrolytic capacitor as good as new - Page 1
Forum section: electronics / general

author: VK3DRB
author_rank: Super Contributor
timestamp: March 06, 2020, 07:25:23 am
content: My plug pack for my 1976 scientific calculator died. I have used that calculator and the original plug pack for 44 years. I opened it up and the transformer had gone open. It did not upset me - these linear plug pack power supplies waste power and are much less efficient than a modern SMPS, so I changed it to a 5V SMPS regulated output plug pack and transplanted the DC connector.Out of curiosity, I tested the 1000uF filtering capacitor which was "Bellcon" brand. I could not believe that after 44 years, the cap measured 1269 uF.It was definitely not made in China, because back then China exported nothing. I suspect the capacitor may have been made in Taiwan. I could find nothing on Bellcon brand, except a few rash statements on blogs by people saying Bellcon are rubbish, without any backup evidence.I have seen many crappy electrolytic capacitors in my day - especially in cheapo radios where they are used for DC blocking in audio output stages and in TV sets.But this capacitor was impressive. The body was in perfect condition. Why didn't the electrolyte dry up at least a bit in all those years?

author: Ranayna
author_rank: Super Contributor
timestamp: March 06, 2020, 07:50:54 am
content: Aren't those generally -20/+80% Tolerance?So it could have lost capacity after all.But to be real, in addition to that there are likely many more contributing factors explaining the remaining capacity. Two come to mind: It is a well made part in general. The cap has probably been made before the drive to extreme penny-pinching. And also severe de-rating. Caps last a log longer if kept cool.There are likely many more reasons for the apparently good condition.And, as far as I understand it, capacity is not everything in a capacitor. It could be deteriorated in other ways that a low voltage/power DMM test cannot detect.

author: floobydust
author_rank: Super Contributor
timestamp: March 06, 2020, 08:15:06 am
content: That Bellcon looks like from Japan? A high percentage I encounter are dried out and low capacity.I think it's due to the rubber bung shrinking and turning rock hard. You can poke it and see.Must have been in high humidity or hand soldered.

author: Bud
author_rank: Super Contributor
timestamp: March 06, 2020, 08:19:32 am
content: I replaced a few of these in my Commodore 64 made in 1984. They seemed to measure OK except for one which experienced high ripple current in the power supply. I did not know how much longer they would last so replaced them anyway.

author: VK3DRB
author_rank: Super Contributor
timestamp: March 06, 2020, 08:46:57 am
content: I lived in Wangaratta for 13 years without air conditioning. We had many days over 100 degrees F. Hottest day was 116 deg F (46.7 deg C). That calculator did not have a comfortable life.The output voltage on the linear supply would have been about 5V or so when the calculator was off and maybe 3V or so when it was on (stamped on the plug pack was" 3V 200mA"), so at least they used a cap rated at least double the DC working voltage. The cap was not mounted on a PCB, but soldered between the common anodes of two discrete diodes joined in mid air and the centre tap on the transformer as a full wave rectifier. The rubber grommet seal is sill soft and there is no discolouration on it.One failure mode of RB type electrolytic caps when mounted flush to a PCB is thermal expansion and contraction that eventually causes them to open circuit. Another is dried up electrolyte. Another was using underrated capacitors to save pennies. This cap suffered from none of this.This Bellcom, whoever they were, obviously made a good quality capacitor. Maybe they were Japanese. I would like to meet the engineer who designed and made this cap, but they are probably long retired or dead. But the cap lives on. I will put it in my spares box along with the two diodes.

author: Zero999
author_rank: Super Contributor
timestamp: March 06, 2020, 09:13:02 am
content: You only measured the capacitance. What's the ESR?

author: Electro Detective
author_rank: Super Contributor
timestamp: March 06, 2020, 10:08:49 am
content: Quote from: Zero999 on March 06, 2020, 09:13:02 amBeat me too itThe casing looks exactly like another brand ELNA from wayyy back when

author: bd139
author_rank: Super Contributor
timestamp: March 06, 2020, 10:12:51 am
content: This one is 58 years old...ESR is about right for the value.ESR meter is the one described here:https://www.eevblog.com/forum/projects/5-transistor-esr-meter-design/

author: Zero999
author_rank: Super Contributor
timestamp: March 06, 2020, 12:01:45 pm
content: Quote from: Electro Detective on March 06, 2020, 10:08:49 amIt's also possible for a capacitor to increase its value, as well as ESR, just as it's about to fail, but it applies to capacitor plague, which is a relatively modern phenomenon, so not applicable here, although it does prove that simply measuring the capacitance, isn't a good enough test.

author: bd139
author_rank: Super Contributor
timestamp: March 06, 2020, 12:04:09 pm
content: I wouldn't trust the ESR either necessarily. I recently repaired something which the capacitors were pissing out electrolyte but the ESR and capacitance were fine.

author: VK3DRB
author_rank: Super Contributor
timestamp: March 06, 2020, 12:20:56 pm
content: Quote from: Zero999 on March 06, 2020, 09:13:02 amESR measured at 0.12 ohms. Not bad for its age.

author: amyk
author_rank: Super Contributor
timestamp: March 07, 2020, 01:22:31 am
content: In my experience,leakycapacitors will often read high on a meter. How much leakage current does it have at 5V?Quote from: bd139 on March 06, 2020, 12:04:09 pmYou won't see any change until the plates start drying. Maybe they were very full of electrolyte.

author: all_repair
author_rank: Frequent Contributor
timestamp: March 07, 2020, 01:28:01 am
content: Quote from: VK3DRB on March 06, 2020, 12:20:56 pmThese well made capacitors most probably can go on for additional 5 year or more, where newly made capacitors with all kind of cost cutting likely last for only 2 years.

author: all_repair
author_rank: Frequent Contributor
timestamp: March 07, 2020, 01:36:12 am
content: Quote from: bd139 on March 06, 2020, 12:04:09 pmA good capacitor tester should include a "stink" indicator. Many time the leak is just at the base, and you have to see closely through the seam between the capacitor base and the PCB, or place your nose close for detection.

author: rsjsouza
author_rank: Super Contributor
timestamp: March 07, 2020, 02:25:44 am
content: I also have very ancient capacitors that are still relatively in spec but, as others have said, other parameters will tell how good a capacitor still is. The dissipation factor (which ESR is one of its components) and leakage will be the measurable specs.My largest capacitor is a Siemens 75mF / 25V and it was manufactured in 1980. It currently shows ~82mF and its leakage hovers around 2mA. The oldest still in good shape fits my 50 year old Power Designs 5015A. The absolute oldest ones are a Philips populating a 1946 Radio (Philips BX462A) and two Teslas from the 1950s. All of them are shot (awaiting time for the equipments to be restored).In my experience, all "Computer-grade" capacitors are the all-time kings of longevity.

author: Bark
author_rank: Newbie
timestamp: March 07, 2020, 03:46:27 pm
content: One of the last things I bought at HSC before they went out of business was this giant bag of Sprague's Vitamin Q capacitors. They are in perfect shape, but look very old. I must have 10 pounds of them, various sizes. Apparently these are hermetically sealed with glass ends!

author: wraper
author_rank: Unknown
timestamp: March 07, 2020, 03:54:30 pm
content: Quote from: Ranayna on March 06, 2020, 07:50:54 amWhen capacitor is not powered, insulating oxide layer becomes thinner and thus capacitance rises but voltage it can withstand drops. High capacitance is not a sign of good capacitor health. If you put this capacitor under rated voltage right away and there is high enough supply current, it might even explode.

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 07, 2020, 03:57:16 pm
content: Yes, also, I would re-test the cap after a few hours of operating time under some reasonable stress - which may show that it has actually degraded.But certainly, well built electrolytic caps that are operated for a long time with very little stress - low voltage, low current, normal temperature - will last a lot longer than if they are constantly operated under a lot more stress (which is common in high-power supply sections.)

author: Seekonk
author_rank: Super Contributor
timestamp: March 07, 2020, 08:12:51 pm
content: I think I have HP's first calculator with a CRT screen and time delay memory. It would mechanically lock up the keyboard when it did a calculation. That has a bad power supply cap giving me a wavey screen. And I thought they used to make good stuff!

author: mcovington
author_rank: Regular Contributor
timestamp: March 08, 2020, 12:38:28 am
content: In equipment that is used tolerably often (at least once every 5 years or so), electrolytics can last a very long time. It is certainly not uncommon for them to go 50 or 70 years. They degrade when *not* used.

author: nctnico
author_rank: Super Contributor
timestamp: March 08, 2020, 12:43:55 am
content: Quote from: all_repair on March 07, 2020, 01:28:01 amNo. Nowadays you can buy electrolytics with a wide variety of life expectancies. Sure if you buy the cheapest one it will be crappy but it doesn't mean you can't buy good ones.

author: mcovington
author_rank: Regular Contributor
timestamp: March 08, 2020, 01:42:24 am
content: Quote from: nctnico on March 08, 2020, 12:43:55 amPrecisely. Here is one rated for 10,000 hours (= more than a year) at 105 C. Depending on how you interpret Arrhenius' Law, that might be more than a century at room temperature!https://www.digikey.com/product-detail/en/panasonic-electronic-components/EEU-FR1V222L/P14450-ND/2433584

author: all_repair
author_rank: Frequent Contributor
timestamp: March 08, 2020, 02:11:24 am
content: Quote from: mcovington on March 08, 2020, 01:42:24 amOn paper, you may be right. I only buy the best one affordable for repair. Exclude those that need 1000 MOQ, or at more than USD10 a piece. I have no data to proof right or wrong, but some practical observations. From the construct of old cap especially at the joints compare to the new ones, they are different. The good old cap are much better. And insulation material decomposes over time, when there is any change to these material, only time can tell would the new materials performed as desired. I have seen equipments that came back 2-3 years later with the new replaced capacitors showing aging and needing replacement but the unreplaced old cap still measured well.

author: james_s
author_rank: Super Contributor
timestamp: March 08, 2020, 04:57:42 am
content: Electrolytic capacitors made in the 1970s that are still good are not rare, I have quite a few in various things. Some applications are much harder on capacitors, switchmode power supplies and CRT displays for example. As a 50/60Hz filter in a low power supply a good quality capacitor can last decades.

author: wraper
author_rank: Unknown
timestamp: March 08, 2020, 10:04:33 am
content: Quote from: all_repair on March 08, 2020, 02:11:24 amProbably because those which were not replaced were not under stress to begin with, unlike those which failed. Also capacitors are often replaced with wrong type. You shouldn't simply put anything even of top brand when replacing capacitors in places with high ripple current like in SMPS. And not all LOW ESR series are equal, rated ripple current can vary drastically.

author: all_repair
author_rank: Frequent Contributor
timestamp: March 08, 2020, 10:22:22 am
content: Quote from: wraper on March 08, 2020, 10:04:33 amAgreed. The failed cap that can affect operation are normally the stressed cap. The original old cap that failed lasted longer than my replaced cap. I don't have the data of how long it was running, my guess was it could have been 10+ or so years. Normally these are running 247 outdoor.