How to Recondition (Reform) Electrolytic Capacitors and Why

[@udiophile99]

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

Current will not be an issue, generally speaking, since you will have the series resistor(s) with the cap(s) to limit current (which is the whole point of reforming the caps, as that will make the voltage rise slowly across them.)

So both the Dell 19.5V and the HP 32/16V chargers will probably work fine. However, for 6.3V, 10V, and 16V caps, you will also need to make a voltage divider before the series resistor(s) so that the voltage is lower. Otherwise, if you use any of the above supplies on let's say 6.3V caps or 10V caps, there's a good chance you'll still damage them even with the series resistor(s) in place, because the supply voltage is too high.

Thus, either connect some kind of a circuit with which you can adjust the voltage from these power adapters *or* do similar to what I showed in post #2 with a voltage divider circuit using some resistors as a crude way to get the voltages needed.

Agree. I think that the Dell 19.5v Laptop Charger will definitely get the job done in the best way possible.

[@udiophile99]

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

I have the following possible power sources available to me. Please comment.

Dell 19.5v Laptop Charger: CON: To connect to breadboard I will need to stuff the inner opening with copper wire and attach a ground wire to the outer surface. I don't want to remove the end piece (makes the thing unusable as a laptop charger). Also this is a 3-wire cable. End pice is 7.5mm, a non-standard size.

HP 32v/16v Printer power supply. PRO: Will work for 25 watt caps, Don't need to remove end piece, just insert wires directly into it. CON: output amps are 720Ma and 610 Ma. Is this a problem?

Respironics power supply. PRO: The end piece is a standard 5.5mm size. I could connect it to a standard socket.

Ryobi battery. PRO: Direct current, no ripple. !8 volt CON: Output Amps too high?

I might also consider using a Buck converter availabe for $30CAD which I could attach to the HP power supply above. I would then only need a dozen of the 1KOhm resistors/

https://www.aliexpress.com/item/3268...c003EYP9R&mp=1

While I'm not exactly an expert, I would say that of every single option you shared with us, the Dell 19.5v Laptop Charger is the one that is definitely going to work as a great power source.

[momaka]

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

Current will not be an issue, generally speaking, since you will have the series resistor(s) with the cap(s) to limit current (which is the whole point of reforming the caps, as that will make the voltage rise slowly across them.)

So both the Dell 19.5V and the HP 32/16V chargers will probably work fine. However, for 6.3V, 10V, and 16V caps, you will also need to make a voltage divider before the series resistor(s) so that the voltage is lower. Otherwise, if you use any of the above supplies on let's say 6.3V caps or 10V caps, there's a good chance you'll still damage them even with the series resistor(s) in place, because the supply voltage is too high.

Thus, either connect some kind of a circuit with which you can adjust the voltage from these power adapters *or* do similar to what I showed in post #2 with a voltage divider circuit using some resistors as a crude way to get the voltages needed.

[bigbeark]

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

I have the following possible power sources available to me. Please comment.

Dell 19.5v Laptop Charger: CON: To connect to breadboard I will need to stuff the inner opening with copper wire and attach a ground wire to the outer surface. I don't want to remove the end piece (makes the thing unusable as a laptop charger). Also this is a 3-wire cable. End pice is 7.5mm, a non-standard size.

HP 32v/16v Printer power supply. PRO: Will work for 25 watt caps, Don't need to remove end piece, just insert wires directly into it. CON: output amps are 720Ma and 610 Ma. Is this a problem?

Respironics power supply. PRO: The end piece is a standard 5.5mm size. I could connect it to a standard socket.

Ryobi battery. PRO: Direct current, no ripple. !8 volt CON: Output Amps too high?

I might also consider using a Buck converter availabe for $30CAD which I could attach to the HP power supply above. I would then only need a dozen of the 1KOhm resistors/

https://www.aliexpress.com/item/3268...c003EYP9R&mp=1

[momaka]

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

Hi, can you show me some simple schema for reform 2000uF/400V Sprague caps?

Probably the easiest thing to do would be to rectify mains (230/240V AC) with a full bridge rectifier, then connect each Sprague 2000 uF, 400V cap, one at a time only, to the DC output of the bridge rectifier. To limit current, use a 10-25 Watt wall-type ("regular") soldering iron and connect in series with the AC live and your bridge rectifier circuit.... i.e. similar to this:

AC live ----> 10-25 Watt soldering iron ----> full bridge rectifier ----> 2000 uF, 400V cap
AC neutral -------------------------------> full bridge rectifier ----> 2000 uF, 400V cap

A 25-Watt soldering iron (or heating element of equivalent power rating) made for 230/240V AC line will have about 2 KOhms resistance, more or less, which is perfect for charging large HV caps without overheating (it's a soldering iron made for 230V AC, after all. )

If you do build this circuit, beware of live/dangerous voltages, of course. And keep in mind your reformed caps will be charged to about 360-370V DC. As such, take good precautions to discharge them carefully and gracefully (using your 10-25W soldering iron to connect across the + and - terminals on the caps after they are reformed and removed from the reforming circuit should discharge them safely.)

[budm]

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

Once you read those information then you will understand the concept then you can apply it to your need.

[koolx]

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

ok

[budm]

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

Read post 1 & 2, you will also need high Voltage power supply. What do you have?
https://www.qsl.net/g3oou/reform.html
https://www.nmr.mgh.harvard.edu/~reese/electrolytics/
http://www.electrojumble.org/reforming.htm
http://www.angelfire.com/electronic/...store_cap.html

[AmidzaDado]

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

Hi, can you show me some simple schema for reform 2000uF/400V Sprague caps?

[momaka]

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

I tested the cap with an analog oscilloscope component tester and all thre sections show a very high ESR, even if the capacitance seem to be ok. I didn't put voltage on and think it had no voltage for more than 20yrs or possibly more...
The cap housing is made of paper, and I think that the hig ESR is due to dried out elecrolyte... If this was the case, I'm afraid the cap regeneration would fail...
Now, the big question: is there some way to regenerate the electrolyte (wich would be some sort of wet compound)?

Unfortunately, no.
I'm not very knowledgeable on old gear and caps, but from what I've read, old paper caps like that have a finite shelf/useful life, as do all "wet" electrolytic caps. Given their age, they are just due for replacement. There is nothing you can do to regenerate the electrolyte. And with their high ESR, chances are nothing will happen even if you do try to "reform" them with a voltage, because more than likely, they have gone "dry" (i.e. electrolyte evaporated or disintegrated or both.)

I will try regeneration, anyway... I've seen that in case of unrecoverable cap one solution to keep it "original" is to pull out everithing and hide new caps inside, but would do as last chance...

If you are trying to keep looks the exact same way, then that's probably your best bet.

I personally don't see anything offensive about old gear with new parts inside (As long as it's done sensibly, of course.) Shows that even the old stuff that's built like a tank won't last forever and needs periodic "updating" on certain components.

[giampi]

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

Hi all, I wrote here as I think it's better than open a new topic. My apologies if it isn't so...
I have to restore a very old guitar amp, trying to get it as close as possible to the original. The circuit is very simple and used only one triple electrolytic cap branded "Planet" model CTC-306 (from the '50 or so, I suppose) wich in a past repair was excluded from the circuit and replaced with three new capacitors. The amp works fine.
I tested the cap with an analog oscilloscope component tester and all thre sections show a very high ESR, even if the capacitance seem to be ok. I didn't put voltage on and think it had no voltage for more than 20yrs or possibly more...
The cap housing is made of paper, and I think that the hig ESR is due to dried out elecrolyte... If this was the case, I'm afraid the cap regeneration would fail...
Now, the big question: is there some way to regenerate the electrolyte (wich would be some sort of wet compound)?
I will try regeneration, anyway... I've seen that in case of unrecoverable cap one solution to keep it "original" is to pull out everithing and hide new caps inside, but would do as last chance...
Any other idea?
Thaks in advance.
Greetings from Italy
Giampietro

[momaka]

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

^ The MOSFETs won't get damaged, but depending on the motherboard, other things might. Case in point, some older AMD and Intel boards from the early and mid-2000's used the CPU V_core also for the chipset (example: Intel Pentium 4 Northwood motherboards with i845 chipset). So in those cases, you'd be feeding a high voltage into some chip that shouldn't be.

With most PSUs, though, I think it should be possible to feed voltage on the output rails to reform the caps. Sometimes I back-feed 12V in my ATX PSUs to run tests on the fan controller circuit.

[socketa]

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

i can see that it's far from ideal (but, perhaps, more practical) to reform the caps collectively in circuit; so how about, in respect to PC motherboards, removing the CPU and then connecting a resistor (which would be, for example, 10Kohm X n, where n= number of VRM input caps) in series with the VRM input caps and applying 16V to it, and after that (after changing the resistor value, and voltage divider, accordingly), to the VRM output caps?
Again, far from ideal, but better than firing up a board that hasn't being used for several years with no reforming
Would applying 16V to the high side, and then 6.3V to the low side, damage the FETS?

[momaka]

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

Would anyone here be able to say:
1. What is the function if the diode in the original post?

It's just for simple reverse polarity circuit protection. That is, if I was to plug in my power supply in backwards by accident (that is negative to positive and positive to negative), the diode would create a short-circuit across the power supply. This will prevent backward voltage feeding into the capacitors and making them go bad.

Since I use mostly SMPS PSUs for my projects, using a diode like that is OK, because the SMPS will simply just power-cycle until I fix the polarity mistake (that is, if the power supply is not too powerful - otherwise the diode would short out permanently.).

2.
Will this also work for new old stock capacitors that are less than 20% of their specified capacitance?

Oh yes, it will work - as in, allow you to plug the NOS caps back into a circuit and not have them blow up or short-out due to oxide layer thinning too much over time.

Reconditioning, however, will _NOT_ restore the original capacitance of the NOS caps. Nor will it restore bad ESR. Reconditioning is simply to "play it safe" before you insert NOS caps in a circuit. And if you ever buy caps and decide to store them, reforming them once in a while (once every 1-2 years.) may help slow down the deterioration rate.

[socketa]

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

Would anyone here be able to say:
1. What is the function if the diode in the original post?
2.

Not only that, but a leaky cap (as in, capacitor with a high leakage current… not one that is physically leaking electrolyte) will usually trick your ESR meter to show lower ESR than what the capacitor may have. So if the cap has gone high ESR, your meter may not show it and you might end up putting a faulty cap back in service. 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 don't have an ESR or capacitance meter (like me ), then definitely reform it so there won't be any doubts.

Will this also work for new old stock capacitors that are less than 20% of their specified capacitance?

[momaka]

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

Further to this discussion, it appears that for anything with electrolytic caps that haven't been used in some years would benefit from first powering on with 60 watt bulb. How about tube devices? Would they also benefit from this?

The series incandescent bulb trick is well-known among restoration techs as an alternative to a variac (and in some cases, even better than a variac, since the bulb limits current too).

[Eaglecrest]

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

Further to this discussion, it appears that for anything with electrolytic caps that haven't been used in some years would benefit from first powering on with 60 watt bulb. How about tube devices? Would they also benefit from this?

[momaka]

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

Momaka, am I correct in understanding that the light bulb places some additional resistance on the device so as to charge caps more slowly and thus limiting them blowing out?

Yes, sort of.

It that is the case then the 100 W bulb will give the greatest protection?

No.
Lower Wattage = slower turn on and greater protection
Higher Wattage = faster turn on, less protection, but allows device to use more power.

With that said, you can't go as low as you like. Some devices will simply not work when the input voltage drops too much (i.e. when using a lower Wattage light bulb). So that's why I suggest 60-100W, as that will work on most amplifiers without trouble. I myself often get lazy and use my 40W soldering iron (it's a simple plug-in iron with a heating element, so it's pretty much the same as using a 40W incandescent light bulb). But I've encountered switch-mode PSUs that won't run with that.

[Eaglecrest]

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

Momaka, am I correct in understanding that the light bulb places some additional resistance on the device so as to charge caps more slowly and thus limiting them blowing out? It that is the case then the 100 W bulb will give the greatest protection?

[momaka]

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

I am assuming this should be in series on the hot side, is that correct? What is the difference in effect between a 60W and a 100W bulb?

Correct, hot side.
Any bulb above 50 Watts should do really, but I generally recommend above 60W. The higher the power rating of bulb, the more current that can be drawn by the device (both at start-up and continuously). 60W will probably allow you to run the amp with a small load. 100 Watts bulb should allow you to crank it up a bit more. Not much of a difference otherwise. I've even used 40 Watt bulbs in a pinch, too - works with devices that have a lower idle power draw.