[Boatanchors] Electrolytic Reforming Time

[rbethman]

So you'll modify the antique anyway.

Too many had the power cords fused in their plugs.

Without punching holes in their chassis' and adding a fuse holder, you 
don't have protection.

Others have some pretty shaky fuse lash-ups under the chassis with cloth 
tubing over them, and NO holder.

Good luck with that!

Then again you don't run transmitters either.

Fuses never did an HT-32 or HT-37 any good when the transformer shorted.

Bob - N0DGN

On 12/31/2011 5:25 PM, J. Forster wrote:
> If you have the unit fused right, even if a cap does eventually fail, it
> won't take the transformer with it.
>
> -John
>
> ===============
>
>
>
>> 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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