How to Recondition (Reform) Electrolytic Capacitors and Why

[Behemot]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

If its fed from the same line, of course it has high current draw. You need some which has independent power supply and only measures. I only know about digital panel voltmeters.

[Per Hansson]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Hi, posting a question here as it's related to the topic.
I built my reformer and used two nice voltage meter LCD's that I got for almost nothing on eBay.
The first one sits before the pot and checks the input voltage from my variable transformer, this works fine.
The second one measures the voltage across the caps being charged, so if I have 6v input it will slowly rise so I know when they are reformed.
The problem is that the input impedance is listed as just 100K, this puts a too big load on the circuit so the caps can't actually be brought to full voltage.
So I'm curious if anyone has seen any voltage monitors like this but with 1M or even ideally 10M input impedance like a real multimeter has?

[eccerr0r]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

See first page.

You absolutely DO need a series resistor for each capacitor. Recommended resistance is 1000 Ohms minimum, as per Panasonic datasheets. I typically use 1 - 15 KOhms, depending on the capacity (lower capacity -> higher series resistance and vice versa).

A 10V supply at 10mA (worst case, as said 10mA is already too high) = 1K ohms.

Just commenting that the heatsink isn't even needed on the design and you could possibly get away with a LM317L or something like that if a constant voltage is even needed ... it just needs to be close enough.

[momaka]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Also if you get an amp of leakage current, or hundreds of milliamps of leakage current, throw it out... make sure you design your LM317T to be current limiting, and for the most part you shouldn't need a heatsink, I'd imagine you don't want to go over 10mA or so when reforming...

...If that even.

See first page.

You absolutely DO need a series resistor for each capacitor. Recommended resistance is 1000 Ohms minimum, as per Panasonic datasheets. I typically use 1 - 15 KOhms, depending on the capacity (lower capacity -> higher series resistance and vice versa).

The 317 regulator should only be used as a constant voltage source and nothing more.

If you see the capacitance much higher than the nominal one, immediately throw it out

Agreed. But we need to quantify that.

From my experiments here, as long as the cap's capacitance is NOT over 30-40% of the rated, then you can try to reform it to see if that restores or improves its specs. And if the cap's capacitance is NOT over 20%, then the cap should still be acceptable to use/reform, provided ESR and leakage current are not reading out of spec too.

[eccerr0r]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Also if you get an amp of leakage current, or hundreds of milliamps of leakage current, throw it out... make sure you design your LM317T to be current limiting, and for the most part you shouldn't need a heatsink, I'd imagine you don't want to go over 10mA or so when reforming...

...If that even.

[watchmaker]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

To avoid this, check the capacitance of the cap. If it is higher than 20% of its specified capacitance, it is likely leaky and it is time to reform it.

If you see the capacitance much higher than the nominal one, immediately throw it out, it will pop in several hours or days of operation. Especially if its production date is between mid-2004 and 2010.

[mockingbird]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Was the pot rated to handle more than 1/2 Watt. If not, that's one reason it could have burned out. Also, if you connect the power source between the pin with variable resistance and one of the fixed resistance pins, turning the pot one way will cause the resistance to decrease and thus possibly allow a lot of current to flow through it and burn out.

Yes, I think this is what I did. Doh! Oh well, it was only a few bucks.

In fact, that is a brilliant idea! The only reason I didn't suggest it is I was trying to keep the circuit simple. Simply wasn't aware you could find a kit for that for such a cheap price. $2 is well worth it, considering a LM317 regulator from Digikey/Mouser is typically at least $1.

Thanks

Yup, the regulators go for between 50 cents to a dollar, depending on the brand and package type. I'm aware that I'm getting a counterfeit one, but who cares, this isn't going to handle more than an amp... Nothing that some backroom Chinese semiconductor lithography couldn't handle.

Nice! Mind posting a link where you found this kit?

Sure. It was this one in particular:
http://www.ebay.ca/itm/301777278859

I'd say DO use their PCB, but only install the components you need for your circuit.

Ok, will do. Thanks again. Can't wait to get started on these caps and start measuring their leakage current.

[momaka]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Is it safe to test these pots without no current limiting load on them?

Yes, but only if you connect it right and don't exceed its current/power handling capability.

By connecting it right, I mean connect the power source between the pot's fixed resistance pins. A 1 KOhm pot with a 24V power source will dissipate 0.576 Watts and 0.024 mA of current.

Because when I was testing it, it burned itself out inside. There's a swiper inside that touches a long, helically-wrapped metal wire. After it burned itself out, there was no constant resistance anymore betwwen one of the pins and the middle, only the variable resistance worked.

Was the pot rated to handle more than 1/2 Watt. If not, that's one reason it could have burned out. Also, if you connect the power source between the pin with variable resistance and one of the fixed resistance pins, turning the pot one way will cause the resistance to decrease and thus possibly allow a lot of current to flow through it and burn out.

edit: momaka - is there any reason why something like an LM317 wouldn't work here?

Not at all.

In fact, that is a brilliant idea! The only reason I didn't suggest it is I was trying to keep the circuit simple. Simply wasn't aware you could find a kit for that for such a cheap price. $2 is well worth it, considering a LM317 regulator from Digikey/Mouser is typically at least $1.

Well, I ordered this kit for about $2... A lot better than experimenting with shoddy POTs, and it can pass a whole lot more current through.

https://www.badcaps.net/forum/attach...1&d=1464282735

Nice! Mind posting a link where you found this kit?

... but I don't think I'm going to be using their PCB, but rather I'll be integrating it on the prototype PCB.

I'd say DO use their PCB, but only install the components you need for your circuit.

I see 5 diodes there. 4 of them could be for a bridge rectifier (which you won't really need if powering this from a DC source), but one of them is likely for protection of the LM317 (which you should install). Not sure what the small TO-92 transistor is for or some of the other components, but I am pretty sure it is one of the application circuits in the LM317 datasheet. So overall, I'd just assemble the whole thing minus the bridge rectifier and possibly the terminals.

Really good kit for that price, though.

As I understand it, the included POT (Those are only rated for 0.08 watts) is only controlling the transistor gate, so the amount of current passing through it is irelevant.

Yes, the pot is controlling the LM317 adjust pin, and the current for that is really small.

[mockingbird]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Well, I ordered this kit for about $2... A lot better than experimenting with shoddy POTs, and it can pass a whole lot more current through.



...not to mention much more cost-effective. Some of the circuit is unecessary, as it's going to be drawing from a DC source, but I don't think I'm going to be using their PCB, but rather I'll be integrating it on the prototype PCB.

As I understand it, the included POT (Those are only rated for 0.08 watts) is only controlling the transistor gate, so the amount of current passing through it is irelevant.

[keeney123]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

What would be a good idea is if the design engineers allowed this to happen in their design. By shutting down the other part of a circuit and only applying the extra needed voltage to the electrolytes. I see this would save a lot of waste.

[mockingbird]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Well, I finally got off my fat bottom and took a serious approach to this project.

What I wanted to ask is about the initial POT for reducing the 24V from my laptop brick. I can't use the wall-wart with the multi-tap transformer and the voltage selection switch because it stopped working.

The problem is that the counterfeit Bourns 1KOhm eBay pot was either garbage, or I may have broken it, and I had to throw it out.

I'm talking about this POT:



Is it safe to test these pots without no current limiting load on them? Because when I was testing it, it burned itself out inside. There's a swiper inside that touches a long, helically-wrapped metal wire. After it burned itself out, there was no constant resistance anymore betwwen one of the pins and the middle, only the variable resistance worked.

edit: momaka - is there any reason why something like an LM317 wouldn't work here? That way I can use bog-standard inexpensive POTs of which I have plenty here just to regulate the 317, and the 317 will be handling the actual current and not the POT.

[alindumitru46]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Sorry , A capacitor can have zero ESR value?! I have measured with a chinese ESR meter like this

[mockingbird]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Finally put an order in for my parts.

Can't wait till it gets here.

[watchmaker]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Which electrolytic capacitors should be reformed?
- Ones that have been sitting in storage for a long time (regardless of whether they are new or used)
- Used capacitors that came from a circuit, where the operating voltage was much lower than the rated voltage of the capacitor.
Example: 6.3V electrolytic caps that were used on the CPU filter output of a motherboard (where the working voltage is often less than 1/3 to 1/4 of the rated voltage.)

It was true only for Russian 80s..90s electrolytic capacitors (but not always), not for modern ones. Many modern capacitors (especially not too good ones) simply die (sometimes even vent or pop) in storage.

[momaka]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

does that mean if i had caps that have gone bad due to abuse, they can be "repaired"?

Probably not.

How did you conclude that they are bad? ESR+capacitance meter?

Generally, if the caps read high ESR (or above normal ESR), they are done.
However, if the capacitance isn't too out-of-tolerance on the high side, this usually indicated high leakage current, which might be reversed somewhat with reforming.

i assume failure without bloating is actually a good sign it can be repaired because the hydrogen gas discharge didnt get out of control for the gas inhibitors?

Not really.
Failure without bulging means the gas probably escaped slowly over time or the electrolyte dried up from heat. A lot of small 5x11 caps die this way. Can't revive them.

The only *real* success I've had with reviving a completely blown cap was by adding water to a popped Sacon FZ. Don't ask why I did that... let's just say I was really bored on a rainy day .
The leakage current was very high afterwards, but I guess capacitance (and possibly ESR too) must have come to spec. Worked fine for speaker DC decoupling, driving a 6 Ohm speaker.
Couldn't believe it when I saw it and couldn't stop laughing for a good 5 minutes either .
That's Sacon FZ for ya!

[mockingbird]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

From what I've gathered from Momaka's great info, it's touch and go.

Start re-forming and keep an eye on the voltage. If the cap's voltage isn't rising along with your own incremental adjustments, then the cap is no good.

[ChaosLegionnaire]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

thanks. very nice article. i have a hoard of sanyo wgs that were made in 2006 and also a breadboard from an electronics workshop i attended waaay back in middle school. havent used that breadboard in decades. hope that breadboard is still good and hasnt rusted, corroded or shorted. i'll wanna use it to reform those sanyos. don't want one of my favourite caps blowing up during actual use...

If you re-form your caps, they will last forever. If you don't you will be throwing them out and buying new ones every few years. As simple as that.

Exactly.
This is why sometimes electrolytic caps are also referred to as "self-healing", meaning that their specs can be brought back simply by applying power to them.

does that mean if i had caps that have gone bad due to abuse, they can be "repaired"? cuz i have some panny FJs that went bad due to a high ripple psu killing the caps. none of them showed signs of bloating. will reforming "repair" those ripple dmged caps? i assume failure without bloating is actually a good sign it can be repaired because the hydrogen gas discharge didnt get out of control for the gas inhibitors?

[mockingbird]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

If you get a 1 KOhm pot and are planning to that 24 V power adapter, then the pot should be rated for 1 Watts. Calculations:
power draw P = (V^2)/R = (24^2)/1000 = 24 • 24 / 1000 = 0.576 Watts

Ok got it.

There are millions of combinations of resistors you can use to get a certain voltage. However, just watch out so that you don't overpower any of the resistors (i.e. force more than 1/2 W through a 1/4W resistor, or something like that). In general, if you are using an adapter of 18 V or above, then try to keep the sum of the resistance of R1 and R2 above in the 1-10 KOhm range.

Yes, I ordered a bunch of 1/2 watt resistors ranging from 1K to around 60K I think.

Why would you need an AC voltage source? Reforming capacitors is done with a DC source only.

I'm trying to create a graph of voltage drop on a rectified transformer based on current draw. I've got to refresh my knowledge on how to macro with LTSpice.

Looks fine.
Are you wire wrapping everything, by the way?

No I'm soldering everything, but I'm using wire-wrapping wire because it's solid core. Also that's what I thought you were using on your breadboard, and I thought it would be a convenient way of placing/pulling jumpers on a breadboard I might purchase in the future other than using bona fide jumper wires.

I think I'll not do more than 10 caps at a time, because I don't want to have to use such a large potentiometer at the source. I think the best way I'll clear things up for myself is if I spend some good time sitting at a desk with all the parts in front of me and extrapolating everything you're saying for myself. That usually helps clear my fog.

Thanks again.

[momaka]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

I'm going the 1/2 watt potentiometer route for now.

If you get a 1 KOhm pot and are planning to that 24 V power adapter, then the pot should be rated for 1 Watts. Calculations:
power draw P = (V^2)/R = (24^2)/1000 = 24 • 24 / 1000 = 0.576 Watts

An alternative would be to use a 1.5 KOhm (or higher) 1/2 W potentiometer.

In the future I hope to build something more permanent with voltage dividers specifically for my wall-wart (ideally I'd like to run a macro in LTSpice which calculates voltages based on different resistor values...)

You don't need LTSpice or any other program to do those calculations for you. If you can add, subtract, multiply, and divide, then you can build simple voltage dividers like I did in post #2 above. The formula is simple:

V_out = V_in • (R2 /(R1 + R2))

where V_in is the input voltage of the power adapter (same as source V1 above), R1 and R2 are the voltage divider resistors, and V_out is the output voltage you get.

There are millions of combinations of resistors you can use to get a certain voltage. However, just watch out so that you don't overpower any of the resistors (i.e. force more than 1/2 W through a 1/4W resistor, or something like that). In general, if you are using an adapter of 18 V or above, then try to keep the sum of the resistance of R1 and R2 above in the 1-10 KOhm range.

but I can't find a way to introduce an AC voltage source into the program).

Why would you need an AC voltage source? Reforming capacitors is done with a DC source only.

Here's my shopping list so far, am I missing anything?

Looks fine.
Are you wire wrapping everything, by the way?

Now assuming I've got two of those ZIF sockets with 14 caps on each, that's 28 caps drawing let's say an average of 30mA each, still less than an amp.

Not sure where you are getting the 30 mA power draw from, but the leakage current of a *working* (i.e. not shorted) capacitor will be much less than that once the cap has charged up: usually 10-300 uA (0.01 to 0.3 mA) and occasionally up to 1 mA (for the really leaky caps). It all depends on how old the cap is and how much it has been abused. See this thread about leakage current:
https://www.badcaps.net/forum/showth...499#post609499

That said, a *fully discharged* capacitor will draw a *peak current* that is limited by the current-limiting series resistor.
Example: 25 V cap that is to be reformed with a 1 KOhm current-limiting series resistor and 24 V power adapter.
Peak current draw:
I_peak = adapter voltage / series resistor resistance
I_peak = 24 / 1000 = 24 mA

If you are reforming 10 caps at a time with the same as the above configuration, the power draw will be 24 • 10 = 240 mA.

*However*, as the caps charge up, the voltage across them will rise. The current draw for each cap after the initial I-peak current will then be:
I = adapter voltage - voltage across cap / series resistor resistance
Let's assume the voltage across the caps has gone up to 10V after a few moments. Then:
I = 24 - 10 / 1000 = 14 / 1000 = 14 mA

Would the 1/2 watt pot be sufficient for this kind of load?

Depends on what you have as the series resistor resistance. The pot will likely burn out if you use 1 KOhm series resistors and do several caps at a time. If you use 10 KOhm series resistors, however, the pot might be able to handle up to 10 caps at a time. Note that I haven't done any "hard" calculations on this, though. But a 1/2 Watt pot will not be able to handle as much power as two separate 1/2 Watt resistors in a voltage divider.

To be honest I never bothered doing that. My rule would be that if a cap can't do its job without reforming then the cap is bad..

Well, let's say you find some really old equipment (like an old amp, for example) and can't find replacement caps or the cost of new ones is too much, then reforming the old ones might be a good idea before plugging the device in and applying power.
I already shorted out a handful before I started experimenting with the cap reformer, so this is definitely something useful to have IMO. I am actually planning to eventually reform all of my caps I have in stock in stock.

It's not a question of "if it needs re-forming it's not good", but rather a question of extending the life of modern electrolytic capacitors to behave within spec for 20+ years after their expiration date.

Exactly.
This is why sometimes electrolytic caps are also referred to as "self-healing", meaning that their specs can be brought back simply by applying power to them.

I would use regulate power supply, you can use LDO regulator and use the pot in the resistor network for setting the output Voltage to adjust for the needed output, and the pot does not have to be high Wattage.

Indeed. Generally, that's how I would do it too, but I only mentioned the simple resistor voltage dividers above to keep costs and complexity to a minimum so that even people with little electronics knowledge can build this.

...you will not see the current draw after the cap is charged up and the spice model of the cap no leakage resistance. Simulator is only as good as how the spice model is created.

Yes.
Also, on that note, caps of various voltages, capacitances, and age will have different leakage currents. A program model, on the other hand, will likely assume new caps and some average leakage current value (if any at all!) So current draw in steady-state (i.e. after the caps have charged up) will likely not be accurate at all in the model.

[budm]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Spice model is very complex: I.E.


http://www.nichicon.co.jp/english/pr...ice/index.html