[ARC5] Reforming Electrolytics attached as PDF

[Michael Bittner]

I have been using my ZM-11A/U RLC Bridge for years to reform electrolytics 
whenever I need one from my decades old stash of same.  It shows voltage and 
current thru the capacitor under test.  I set the voltage such that the 
current is no more than 5 mA and as the capacitor reforms this current 
gradually comes down.  I then raise the voltage again, and so on until the 
voltage rating of the cap is reached and the current is well under 1 mA.  If 
there comes a point where the current fails to come down to an acceptable 
level at its voltage rating, I toss out the cap.    Mike. W6MAB


----- Original Message ----- 
From: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
To: <arc5 at mailman.qth.net>
Sent: Monday, March 19, 2018 11:46 AM
Subject: Re: [ARC5] Reforming Electrolytics attached as PDF


>    It should be understood that there is both series and parallel 
> resistance in a capacitor. ESR may be less important than parallel 
> resistance, which is also called leakage.
>    All electrolytic capacitors have leakage and it is the leakage that 
> ruins them when it becomes too low. ESR, also called Dissipation Factor, 
> is a measure of the Q of a capacitor while parallel resistance or leakage 
> measures the amount of DC is passes.
>    Ageing without voltage may reduce the thickness of the dielectric 
> layer. This will lower the effective voltage rating of the capacitor and 
> may raise its capacitance, but may not affect its leakage. A high leakage 
> capacitor of any kind may measure OK for both value and ESR so both kinds 
> of measurement are necessary. The leakage is measured by testing for 
> current through the cap. An ideal capacitor should not pass any DC 
> current. Practical electrolytics always have some. The old capacitor 
> checkers of the sort with a magic eye indicator were leakage testers. They 
> usually have a variable DC source for electrolytics and a means, often the 
> eye tube, for indicating leakage current.
>     I don't think reforming will help leakage.
>     A typical impedance bridge does NOT measure leakage although it may 
> give a value for parallel resistance. These two are confusing because they 
> use the same name for different things. An impedance bridge may indicate 
> either series or parallel resistance depending on its configuration and 
> range but, unless it of the kind that has a DC source for the capactor it 
> will not indicate leakage resistance.
>     Leakage may not be apparent with a low test voltage because it may be 
> due to break down of the dielectric at some voltage. However, it may show 
> up even with a conventional ohm meter when it reaches high value. I have 
> bad electrolytics that show bad on a Hewlett-Packard 410-B VTVM ohm range 
> and also show bad on a General Radio Megohm meter and also on an old Eico 
> capacitor tester. They are just bad.
>     Storage in a capacitor is another way of measuring leakage. ESR will 
> not affect the rate at which a charge is lost, that is due to parallel 
> resistance. It is partly a property of the electrolytic and partly of the 
> insulation of the capacitor body. Good non-electrolytic caps can hold a 
> charge for years.
>     There are other properties of capacitors such as dielectric absorption 
> AKA voltage recovery, which can be critical in some applications and 
> unimportant in others. This is the effect of a capacitor not fully 
> discharging when shorted. After the terminals are opened again some 
> voltage, often considerable appears across them. This can be very 
> important in capacitors intended for timing and low frequency 
> applications. Mica caps have a lot of absorption, paper is low in 
> absorption and plastic has very little. It is of no importance in the 
> usual applications for electrolytic caps.
>
>
>
> On 3/19/2018 10:43 AM, Kenneth G. Gordon wrote:
>> On 19 Mar 2018 at 10:06, Bob kb8tq wrote:
>>
>>>      His method is to reform the electrolytic VERY SLOWLY, with a B+ 
>>> source limited to
>>>      FIVE MA., while monitoring the Cap voltage.
>>
>> This is EXACTLY what that military document I posted says: 5 mA, no more, 
>> over a long
>> period of time.
>>
>> Some of us use 1 mA, which may actually be too low. Testing is required.
>>
>> I also have and use an ESR meter.
>>
>> Ken W7EKB
>
> -- 
> Richard Knoppow
> 1oldlens1 at ix.netcom.com
> WB6KBL
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html 


---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus