[Boatanchors] Electrolytic Reforming Time

[lee]

Carl and others,

I agree, using old electrolytics even when reformed is foolishness.   My 
suggestion to those doing so is, right after installation of a 50 year old 
cap which was designed to last around 6 years is to immediately buy an 
insurance policy on your apparatus and then make a copy of this e-mail. 
When the thing blows up in your face, read the warning e-mail, and please 
don't wine on the list when it fails, and it will fail.

To be honest I am beginning to wonder why I belong to any list knowingly 
suggesting this type of foolishness.  As a learning experience, reforming is 
just fine or used in an emergency which I cannot see happening with anyone 
on this list.  Doing so for some old piece of junk and not caring if the 
thing blows up may be one other exception.  For the life of me,  I cannot 
understand why someone would want to install a time bomb in his pet 
historical project, take the time to do it, and at the same time avoid using 
a modern, fresh, and better made capacitor which today costs very little. 
You can rebuild an old three section can electrolytic for $5-$10 or buy 450 
volt axials for less then $5 each.

You won't find me playing Russian Rue let with my old equipment using this 
bad practice.

Lee, w0vt


-----Original Message----- 
From: Geoff
Sent: Saturday, December 31, 2011 4:20 PM
To: W9RAN at oneradio.net ; boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] Electrolytic Reforming Time

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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