[Boatanchors] Electrolytic Reforming Time

[Geoff]

Id tend to flip those percentages to maybe 10-20% and thats with very high 
quality caps and some fairly late ones.

It seems to me that we only hear from the same "reformers" over and over and 
the failed ones are very silent while licking their wounds and searching for 
new transformers or a rewinder.

Just my $.02

Carl
KM1H



----- Original Message ----- 
From: "Robert Nickels" <ranickel at comcast.net>
To: <boatanchors at mailman.qth.net>
Sent: Saturday, December 31, 2011 4:32 PM
Subject: Re: [Boatanchors] Electrolytic Reforming Time


> On 12/30/2011 11:50 PM, Phil wrote:
>> So, it doesn't pay to take any chances with those 'lytics.
> I agree with all that's been said but would just add that this business
> of "bringing it up slowly on a variac" should be relegated to the urban
> legends file.  It's better than just applying full AC power, but is
> still guesswork.   The only way to properly reform an electrolytic -
> regardless of age - is to limit (and measure) the amount of current
> being applied to attempt to "reform" the anode oxide layer that was
> "formed" at the factory when the cap was manufactured.
>
> A good description of how the aluminum electrolytic capacitor works can
> be found here:
> http://www.elna-america.com/tech_al_principles.php
>
> And here's a good reference for how to reform capacitors properly as
> well as some alternatives:
> http://www.nmr.mgh.harvard.edu/~reese/electrolytics/
>
> I prefer to measure and limit the current to about 5 ma while the oxide
> layer is reforming; trying to do the job by simply cranking up a variac
> every so often might work some of the time, but is like tuning your rig
> while blindfolded.
>
> I generally just replace electroyltics that are  cheap and readily
> available and attempt to reform those that aren't.  I think most
> "reformers" find the process can restore 80-90% of old caps when done
> right, without fear of explosions or failure.
>
> 73, Bob W9RAN
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