[Boatanchors] Electrolytic Reforming Time

Sat Dec 31 17:55:17 EST 2011

That's your (incorrect) reading of what I wrote.

Sea and ground based Mil gear has fuses. The value specified should not be
exceeded.

Airborn equipment sometimes relys on external breakers or fuses. Those
should be of the correct type and rating also, and connected as originally
intended.

I have seen several pieces of equipment damaged or destroyed by incorrect
overfusing, often because a previous owner didn't ask why a fuse blew.

And I don't drill holes in gear.

-John

================

> 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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>>
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>
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