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Author Topic: REFORM NOS CAPACITORS WITHOUT EXPENSIVE EQUIPMENT  (Read 217 times)

N8CHR

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REFORM NOS CAPACITORS WITHOUT EXPENSIVE EQUIPMENT
« on: October 27, 2022, 09:21:58 AM »

I have some electrolic capacitors I want to use in a power supply. They are NOS. How can I reform them without expensive equipment? Been setting around for years.
Thanks TOM N8CHR
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W9WQA

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Re: REFORM NOS CAPACITORS WITHOUT EXPENSIVE EQUIPMENT
« Reply #1 on: October 27, 2022, 10:13:33 AM »

have some...?
just put one in!
prob fine...
i rarely have bad caps.
some guys do...
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K5LXP

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Re: REFORM NOS CAPACITORS WITHOUT EXPENSIVE EQUIPMENT
« Reply #2 on: October 27, 2022, 10:19:46 AM »

If you mistrust them to the point you think they need reforming, consider buying new and mitigating reliability issues later.  You could power them up with some series resistance on a bench supply as a sanity check but I wouldn't trust that 're-forming' would restore an old/weak cap to full reliability.

Mark K5LXP
Albuquerque, NM
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W0RW

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Re: REFORM NOS CAPACITORS WITHOUT EXPENSIVE EQUIPMENT
« Reply #3 on: October 27, 2022, 10:35:46 AM »

Check out   MIL-HDBK-1131,
 STORAGE SHELF LIFE AND REFORMING PROCEDURES FOR ALUMINUM ELECTROLYTIC FIXED CAPACITORS.
http://everyspec.com/MIL-HDBK/MIL-HDBK-1000-1299/MIL_HDBK_1131_1788/
Paul   w0rw
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N8NK

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Re: REFORM NOS CAPACITORS WITHOUT EXPENSIVE EQUIPMENT
« Reply #4 on: October 27, 2022, 11:01:48 AM »

Install caps in device.
Energise with Variac, increasing voltate in 5 steps or so to full voltage input.
Done.
I do this only with serious vintage caps in order to do a first test to discover other defective components, etc. I do this with pre- WWII and post- WWII radios.
If it's from the 70s or 80s - just plug it in and turn on.
My opinions. Since I uttered them  :)
Blowzo the Humble Ham
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KD6VXI

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Re: REFORM NOS CAPACITORS WITHOUT EXPENSIVE EQUIPMENT
« Reply #5 on: October 27, 2022, 12:35:04 PM »

p21: http://www.chemi-con.co.jp/e/catalog/pdf/al-e/al-all-e1001u-2020.pdf
P11: https://industrial.panasonic.com/content/data/CP/PDF/Alumi/Alumi_TechnicalGuide_e.pdf
P13: https://exxelia.com/uploads/PDF/5e5e5f3a1ffc1.pdf
P24: https://www.dfrsolutions.com/hubfs/Resources/services/Long-Term-Storage-of-Al-E-Capacitors.pdf
Siemens equipment : https://support.industry.siemens.com/tf//WW/en/posts/reforming-the-harmony-cell-electrolytic-capacitors-for-gen-iv/107349?page=0&pageSize=10


Though in my opinion, reforming a capacitor is BS.  If the cap is either on the ragged edge today or ready to short today, replace it.

A lot of the transformers, etc. in power supplies used in equipment old enough to 'reform' is made of unobtanium. 

This can take out transformers, chokes, rectifiers.  What's the point?  To save 20 bucks?

We don't follow such mythological bs here at work.  Rockwell / AB says to put their VFD drives (which have very large capacitor banks in them) on full voltage once a year, overnight.  If it hasn't been used in 5 years, then the capacitors are no good.  We can replace them (we don't), send them in to be replaced (sometimes), or scrap them (my favorite, I keep the heatsinks for class E and other projects).  No point in doing things half a$$ed.

--Shane
WP2ASS / ex KD6VXI
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