reform old electrolytic capacitor

[tiago1986]

Please can any specialist help me I've read a lot about the subject but I still have doubts electrolytic capacitors of any brand, manufactured in the early 90's (31 years old) and mounted in electronic circuit, need reform after what maximum interval of time? the only reform I do doesn't use a resistor, just connect the device to the power with the plug

[Shock]

They mean by reforming, limiting the current on purpose to allow the capacitor to gracefully lower it's internal leakage value back into tolerance.

Switching the device on from cold when it's been left unused for a decade is not reforming but if you use the device every 6 to 12 months it should reduce the chance of failure soon after power up.

What it won't stop is poor quality caps physically leaking, falling out of tolerance or attrition due to the natural end of life of that capacitor series. So often it's easier and more cost effective just to replace old capacitors if you plan to keep the device rather than checking them one by one.

The other way is look up if the device is being recapped by others or mentions of problems with that brand/series and age of cap.

[tiago1986]

why some electrolytic capacitor manufacturers say 2 years and others 3 years? their suggestion is for new unused electrolytic capacitors and were from the electronic circuit and a reputable brand? is my case different?

[Shock]

The storage period before reforming doesn't indicate quality or reliability, different brands and series will have different specifications. The capacitor might not outright fail if used past that 2-3 year point, just a greater chance of it degrading in performance if not reformed first.

When the device is used in normal operation the capacitors self heal. So as I said use the device periodically or replace the capacitors outright you are worried. Reform capacitors you have had sitting around before using them in a circuit/device (if you want to get the best life possible).

[Faringdon]

Please can any specialist help me I've read a lot about the subject but I still have doubts electrolytic capacitors of any brand, manufactured in the early 90's (31 years old) and mounted in electronic circuit, need reform after what maximum interval of time? the only reform I do doesn't use a resistor, just connect the device to the power with the plug

Yes, reform after  2 years.

If you dont know, get one cap thats been in store for 3 years...put a small current sensor in series with it.......suddenly connect it to 0.9* rated vout...........note the leakage current, and its duration, if its too big, then reform them with the  1k(?) resistor.

But yes, i always wonder how anyone can tell how old a capacitor is...the manufacture data is not printed on them.

[tiago1986]

their suggestion 2 years is for new unused electrolytic capacitors and were from the electronic circuit and a reputable brand? is my case different?

[Shock]

The manufacturer is not going to recommend you remove old capacitors from devices to reform them. But they develop the same problem over time if left unused.

[tiago1986]

if they say 2 years for new electrolytic capacitor then my devices is less than 2 years because the capacitors were made in the early 90's?

[Shock]

1. Unused (old or new, in or out of device) electrolytic capacitors - reforming may prevent damage prior to using. Test for capacitance and leakage after reforming.

2. Capacitors made in 1990s are becoming end of life. Best to test and replace small and medium sized capacitors especially if used under high stress (smps, near heat sources, high hours).

Understand?

[james_s]

The only time I have ever reformed an old electrolytic capacitor was in a ~70 year old radio, and I only did that for some initial testing before I could get a proper replacement. I have powered on equipment that has sat for a decade or more on numerous occasions and never did anything special, I just plugged it in and turned it on. Never had an issue.

[Shock]

The more money it costs to replace the more I care.

[tiago1986]

I thought that two years indicated by the manufacturer was only for new electrolytic capacitors out of circuit

[Shock]

The leakage in electrolytic caps will increase over time if no voltage is applied. As I said the manufacturer will not recommend you remove old capacitors from devices to reform them.

You can use this crude and very slow method to measure leakage and reform. The 10M impedance of the digital multimeters voltage function does the current limiting. Take the measurement and calculate current using ohms law. Don't exceed the voltage rating of the capacitor with your power source.

It will take quite a while to charge (especially if already leaky) so use a switch or short the wires if you want to fast charge an already recently used capacitor (wear safety glasses).

[tiago1986]

I don't use this method of reform because it's complicated the electrolytic capacitors are inside the electronics devices 90s  I just connect the device to the electrical network in my house but I need the maximum interval allowed to turn them on without damaging the electrolytic capacitors

[Shock]

As I suggested, if you are concerned about the capacitors in a 30 year old device then power it on every 6-12 months (for a few hours while being in the room). I do this to my expensive tube amps, I'm not worried about losing a capacitor, but losing a tube or transformer unnecessarily is painful.

[f4eru]

it's complicated the electrolytic capacitors are inside the electronics devices

Yep, the simplest way in this case to lower the risk significantly is to power up very very slowly using a variac.

[Shock]

Yep, the simplest way in this case to lower the risk significantly is to power up very very slowly using a variac.

As was pointed out to me a while back and a fair comment, an exception is switching power supplies can fail on variacs. Some at low voltage and some with pfc, some auto line detection switching. Even if you had a low voltage robust smps with a wide line input voltage, it's not switching until approx 80-90V and then once it starts the circuit draws full load.

Variacs are more useful instead for soft starting linear transformer powered devices like old radios, amps. As well as testing power supplies, ironically including smps for over/under voltage robustness.

Another point is capacitors don't fail immediately. I recently had some fail after 10 hours on an aging amp that had been unused for about 5-10 years prior to me owning it. So for your own equipment it makes more sense to power them on periodically, and proactively replace as needed before damaging other components.

[BrokenYugo]

Once a year is probably adequate, you aren't going to find any hard data for this sort of thing.

[tiago1986]

manufacturers say 2 years but 6-12 months is more reliable? do you have any study on this issue?

[Shock]

The manufacturers specification is for proper reforming out of circuit and near new capacitors. There is no data for some unknown capacitor brand/series specifications in unknown condition operating in an unknown device at an unknown temperature after 30 years.

It's reasonable to assume that if the device has capacitors in spec (without prior damage) after 30 years that every 6 (paranoid) to 12 (acceptable) months for a few hours, the capacitors will continue to have enough time to self heal. Assuming you don't do something stupid like place maximum operational stress on the device immediately after turning it on as well as addressing things like renewing thermal grease, conductive glues, tin whiskers (name your age related problem here) and keeping the device in dust and vermin free environment with good humidity and temperature control.

So yeah 6-12 months I reckon, but I have the sneaking suspicion you are a 6 months or never type of guy.

[Shock]

You already asked the same question months ago and got a similar answer. I noticed that thread has been locked. Restarting the conversation of a moderator locked thread is a forum crime against humanity similar to cross posting.

Now that I see you own vintage collectables I think you are a 6 months type of guy. I'll also warn you that smd electrolytics, batteries have a high chance of physical leakage and don't forget to investigate the cartridges and accessories. The 80s gear has a lot of problems with aging roms, regulators, physical leakage causing board corrosion, capacitors failing causing damage to sensitive circuits. I'd also pickup some broken spare console boards as you can assume some parts will be hard to obtain in the future as the price increases.

https://www.eevblog.com/forum/renewable-energy/electronics-devices-1990-store-for-not-failed-electrolytic-capacitors/msg3554983/#msg3554983

Probably the best way to store anything with electrolytics in it for a long time would be to power them up occasionally to prevent the electrolytic caps from deforming.  (Once every six months?) Other than that, keep it in a DRY environment and as cool (non-condensation) temperature as possible. Lower temperatures will slow down any chemical reactions that could degrade the caps. It would probably help if you could store it in a vacuum or in some sort of inert gas or nitrogen but that's probably not practical. Oh, and put desiccant in the container too, and take out any batteries that are in the equipment!

I recently bought a big military automotive electrical system tester that has been in storage since it was refurbished (by the GOV) in 1978. I don't know how it was stored originally but it still has bags of desiccant still inside of the aluminum shipping/storage case and it is in excellent condition.

That example Stray Electron gives was military grade and over engineered. Smd electrolytic capacitors from around the 90s are way more likely to ruin your day than a through hole with internal leakage.

[tiago1986]

Has any test shown how stored non-new electrolytic capacitors of any brand and in electronic circuit behave?

indeed some say 6 months or 1 year but how did you come to this conclusion?

I will follow your advice thank you

can be 1 hour the connected device working for total reform?

[Shock]

I'd do a few hours initially if not been powered on in while and an hour every 6 months should be fine. If you get one that heaves it's guts and corrodes the pcb refer back to my warning about old capacitors and testing them properly. It doesn't hurt leaving devices on, just don't leave them unattended.

Your other questions have been already answered, both threads have good advice. I'm done here.

[tiago1986]

using electronic devices every 12 months for 1 hour is good or bad for prevent fail electrolytic capacitors?

[f4eru]

yes it is.

The variac killing a PSU is unlikely: every properly designed PSU can cope with low voltages without failure.
Modern PSUs all have UVLO and current limits.