Doubt electrolytic capacitors

[cloudff7]

I have electronic devices from the early 90s in storage, turning them on for 1 hour (60 minutes) Is it good or bad to prevent all electrolytic capacitor failures due to disuse?

 

[TonyTecson]

capacitor seals are the weak points, cause dry-ups over a long time...

 

[rayma]

If the devices are not expensive, Bring them up slowly on a fused Variac, over perhaps 30-60 minutes.
Then cook them for a couple of hours. Watch them the entire time though.

If they are expensive, it's best to just replace the caps.

 

[TonyTecson]

if no electrolytic caps pop within a 1 hour power soak, chances are they are good...

just like your car that you need to run your car engine for a short time everyday, that can help...

but then again, caps fail in time, nothing you can do to prevent that eventual failing..

 

[cloudff7]

I have kept store devices from the early 90s (snes, crt tv) and devices from the early 2000s (crt tv ps2 slim) and some recent devices, they all have electrolytic capacitors and work well

Is there any reliable study showing whether turning on these electronic devices for 1 hour (60 minutes) is enough to avoid problems with electrolytic capacitors due to disuse?

Is there another study indicating a safe time interval for turning on these devices to preserve the electrolytic capacitors?

 

[jan.didden]

Those caps deteriorate due to dry-out. It happens over time.
I don't think it makes a difference whether they are on or off any time.
Since the failure occurs at the moment they are powered on again, to extend the life don't power them on until you really have to.

Jan

 

[AjohnL]

If you want you could read this
https://digital.library.unt.edu/ark:/67531/metadc3104/m2/1/high_res_d/thesis.pdf
What it mostly boils down to is similar to use - degradation of the cap's characteristics that may recover in use,

Fact is there is always the possibility of a cap going AWOL when it is in use. Even going pop.

The paper's comment about a manufacturer's shelf life statements are correct - it's rather odd. In one case many many years in use and a lot less on a shelf.

 

[cloudff7]

I read that turning these devices on from time to time prevents some problems with the electrolytic capacitors caused by disuse

But I have two doubts and I wanted to know if there is any study proving this information

1) turning on electronic devices for 1 hour (60 minutes) is it sufficient or not to reform all electrolytic capacitors and minimize damage due to disuse, some people say several hours, other people say 1 hour, other people say 30 minutes

2) what is the recommended time interval for turning on all devices that have electrolytic capacitors to avoid failures due to disuse

 

[TonyTecson]

if your cap will sit on the shelf for a long time, make it a point to short out the terminals to prevent charge build ups, safe practice too...

 

[cloudff7]

1) turning on electronic devices for 1 hour (60 minutes) is it sufficient or not to reform all electrolytic capacitors and minimize damage due to disuse, some people say several hours, other people say 1 hour, other people say 30 minutes

2) what is the recommended time interval for turning on all devices that have electrolytic capacitors to avoid failures due to disuse

 

[benb]

I think a minute every six months will keep the electrolytics formed. The one-hour recommendation warms things up and help drive moisture out of the power transformer.

If it's been unplugged for several years, there's the risk that the large capacitors in the power supply are un-formed, and the sudden application of operating voltage could make them overheat and explode. They should be brought up to rated voltage slowly with a low current such a 10mA. You have to take them out of the circuit to do this.

Here's a good video on reforming:

 

[cloudff7]

One minute is too little to reform the electrolytic capacitors in the circuit of the electronic device, is there any study on this question? electrolytic capacitors were in the circuit with resistor for many hours

 

[TonyTecson]

when reforming caps, what is important is that the leakage current is decreasing over time, below 1mA is a good number....when the ecap reforming voltage has reached the working voltage on the label..

 

[cloudff7]

this is for single electrolytic capacitors outside the circuit in my case they are electrolytic capacitors mounted on the PCB circuit of electronic devices

 

[AjohnL]

1) turning on electronic devices for 1 hour (60 minutes) is it sufficient or not to reform all electrolytic capacitors and minimize damage due to disuse, some people say several hours, other people say 1 hour, other people say 30 minutes

The video points out that there isn't one. Also refers to sources about how it should be done. It also mentions that they may not be fully recovered to as new specification. I'd say they are unlikely to be. It's rather like trying to recover an over discharged car battery. The chemistry is messed up.

The main reason someone might choose to just power up some old equipment is to check to see if there are problems. If it was an amp they might also run it fully loaded for a while perhaps with a resistive load. So all looks ok - they are still old capacitors.

So all looks ok so time to open up to see what is going on in electronic terms. If concerned take precaution allthough I would expect an electrolytic case to just split if it has this sort of problem not explode. This could happen when ever kit is opened up. How many people do take precautions?

I have had direct experience of a film type capacitor literally exploding. The lamp brightness control in an old microscope. Rather small part, 240v main. A failure could result in it taking kw's. Good job the board it was on was within the casing.

 

[cloudff7]

So if an electrolytic capacitor spends years without being energized, it won't fail due to disuse?

 

[mdpaudio]

They dry out with time used or unused. Running them once in a while keeps them formed to maintain value and voltage rating but they can still dry out. Once dried out the material inside collapses often shorting the cap out. When this happens the cap can heat up and even pop when it is used again. Nasty smell and a bug gooey mess to deal with. Quality caps will often last 20+ years if not stored in hot places. An attic will kill a cap faster than a hall closet. If the equipment is all analog with no switching supplies or digital circuitry you can bring it up slowly on a variac over an hour to full voltage. That will help reform the caps if they are not dried out. Bottom line is if the equipment is valuable just change out the caps and you’re good for another 20+ years. If you are just doing this for fun, go for it!

 

[cloudff7]

In my case, the devices work normally when they are devices from the early 90s and early 2000s, but it is very difficult for me to remove all the electrolytic capacitors to renovate them, so I asked if I could turn on all the devices for 1 hour (60 minutes) is it sufficient or not to completely reform all electrolytic capacitors

 

[Mark Tillotson]

if your cap will sit on the shelf for a long time, make it a point to short out the terminals to prevent charge build ups, safe practice too...

That's only useful for high voltage capacitors where the voltage creep-back might become dangerous - low voltage caps not an issue.

1) turning on electronic devices for 1 hour (60 minutes) is it sufficient or not to reform all electrolytic capacitors and minimize damage due to disuse, some people say several hours, other people say 1 hour, other people say 30 minutes

2) what is the recommended time interval for turning on all devices that have electrolytic capacitors to avoid failures due to disuse

More complicated than that - for low voltages its less crucial as the power dissipated in leaky parts of the cap won't cause much heating. For high voltage capacitors leakage during reforming can involve a fair amount of power dissipation - which is why high voltage caps are typically reformed by gradually increasing the voltage while monitoring the leakage current.

I'd personally not both with any precautions for say +/-15V equipment - just turn it on, it'll reform itself without drama. Well, if its a massive bank of giant caps perhaps reconsider...

For valve equipment that's been idle for decades, definitely bring up gradually with a variac.

For high voltage caps (say 50V or more) in long term storage, again worth bringing up gradually and monitoring the leakage current - though high voltage variable DC supplies aren't a commonplace thing. You can simply use a series resistor to limit leakage current to somewhat more than the datasheet nominal leakage current and apply full voltage - that will limit leakage to a safe value and let the voltage rise as it reforms, just monitor the cap voltage, as it gets close to full voltage you may have to reduce the resistance. Be sure to check the resistor wattage is sufficient, and definitely get the cap polarity right or it may burst!

Or simply buy new electrolytics which will thus have a longer more predictable life and probably be more compact...

 

[Ian Finch]

It should be clear from the several replies and video already, that whatever approach is used, reforming can't replace dried-out electrolyte and typically doesn't help with solid state power amplifiers at all. Anyway, if you want to try to reform all the power supply caps at the same time, you need to use a variac or perhaps a lower AC power source to do this safely, by allowing you to raise the mains power (i.e. the AC supply) gradually. Don't simply apply full power to the power amplifier though - unless you are prepared to clean up a likely mess of burst caps and corrosive debris.

Otherwise, a dried-out cap can't be repaired by any means. It's dead - replace it or just listen to the buzz of AC power instead of audio.