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 Post subject: Reform NOS Capacitors?
PostPosted: Aug Thu 12, 2021 7:18 pm 
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Location: Belleview, FL 34420
I bought six new axial capacitors marked BC Elco. 220uF @ 500 volts. Not sure how long the capacitors have sit on a shelf unused, packaging looks newer (see pix). Only source for new 220uF @ 450 volt are from Mouser at $27 each. I paid $30 for all six BC Elco capacitors. The caps will be placed in a Collins 30L-1 amplifier and will have 300 volts applied to each cap. Only power source I have for reforming is about 80ma from an old tube radio. I could make a voltage divider and apply about 150 volts and increase to 300 volts. Or, can I simply install in amp and not worry about it as they are only operating at 60% voltage rating in the amp. Your thoughts?


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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Thu 12, 2021 8:38 pm 
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You can check them for leakage with your power supply and a meter, or a Sprague TO-5 or something; chances are pretty good they won't need to be reformed


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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Fri 13, 2021 3:25 am 
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80mA at what voltage? You want to get at or near their rated voltage when checking leakage current. I'd put them in series with a 10K resistor and your DVM, then check the leakage after 10 or 20 minutes.

Edit: Moved "?" and added period after "current".

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Last edited by Mikeinkcmo on Aug Fri 27, 2021 10:57 am, edited 1 time in total.

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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Fri 13, 2021 2:37 pm 
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Mikeinkcmo wrote:
80mA at what voltage, you want to get at or near their rated voltage when checking leakage current? I'd put them in series with a 10K resistor and your DVM, then check the leakage after 10 or 20 minutes.

I stated at 300 volts maximum from the power supply in my Crosley radio. I pull all tubes except the rectifier and voltage should rise to about 300 volts

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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Fri 13, 2021 3:57 pm 
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Not to discourage reforming but you can do better than $27 for caps with same specs from Mouser.


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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Fri 13, 2021 4:45 pm 
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Location: S. Dartmouth MA 02748-1225 USA
IMHO Caps for transmitters, often in series to be used at high voltage, really, should be the best quality, with very low ESR.

I would not feel comfortable to use electrolytic caps that are at least 5 years old, may be from different manufacturing lots and to be connected in series...

I would use the freshest I could get with low ESR rating and possibly known to function O.K. in such an environment. I would also be sure the rectifiers are in top condition. Somehow disaster in such a power supply could really be a mess...

Its fine to be frugal but do that by locating the desired quality part by brand name then shop for the best distributor price. Generally, large distributors have a high turn-over buy larger component lots at deep manufacturer discounts. Often, pass that on to the buyers.

GL Chas

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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Fri 13, 2021 5:05 pm 
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Dale Saukerson wrote:
Not to discourage reforming but you can do better than $27 for caps with same specs from Mouser.
Not axial caps. Prefer axial type that is what the Collins 30L-1 supplied. But, Chas changed my thinking about the Collins 30L-1 replacement capacitors as stated below.

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Last edited by jimbenedict on Aug Fri 13, 2021 5:27 pm, edited 1 time in total.

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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Fri 13, 2021 5:08 pm 
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Location: Belleview, FL 34420
Chas wrote:
IMHO Caps for transmitters, often in series to be used at high voltage, really, should be the best quality, with very low ESR.

I would not feel comfortable to use electrolytic caps that are at least 5 years old, may be from different manufacturing lots and to be connected in series...

I would use the freshest I could get with low ESR rating and possibly known to function O.K. in such an environment. I would also be sure the rectifiers are in top condition. Somehow disaster in such a power supply could really be a mess...

Its fine to be frugal but do that by locating the desired quality part by brand name then shop for the best distributor price. Generally, large distributors have a high turn-over buy larger component lots at deep manufacturer discounts. Often, pass that on to the buyers.

GL Chas

I decided to follow your advice . Ordered from Mouser six Nicholson caps rated 220uF @ 450 volts with a huge 1.5 amp ripple current rating. Diodes were changed to modern 1N4007 for 4KV per leg in a bridge configuration with 1800 VDC unloaded and 1600 VDC loaded using SSB service.

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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Fri 13, 2021 7:39 pm 
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I know it is tangential to the thread, but 80 mA to reform capacitors? That's likely to lead to grief. Think about it: 300 volts at 80 mA is 24 watts of power being dumped into a capacitor that isn't designed to dissipate anywhere that much heat.

The one thing you do not want to do with any electrolytic is cause internal heating--especially if the dielectric layer has deteriorated because the caps sat around a while. Pushed hard enough you can vent the electrolyte or damage the plates badly enough to short the cap permanently. For caps of the size shown I would not allow reforming current to exceed 5 mA. I'll go to 10 mA for aluminum can electrolytics which are bigger and better able to deal with internal heating.

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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Fri 13, 2021 10:31 pm 
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Location: Belleview, FL 34420
I say saying I got 80ma available from the power supply. If a cap draws perhaps more than 10ma each. it would overheat.

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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Fri 13, 2021 11:06 pm 
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jimbenedict wrote:
I bought six new axial capacitors marked BC Elco. 220uF @ 500 volts. Not sure how long the capacitors have sit on a shelf unused, packaging looks newer (see pix). Only source for new 220uF @ 450 volt are from Mouser at $27 each.


Sal has new SnapIn 220uf @ 450v radial for $2 each.
Just solder leads onto the snap connectors.


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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Sat 21, 2021 8:20 pm 
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Location: New York City, New York
Curious why you are using 220uf when the Collins uses 100uf.

You can get 6 100uf Illinois 450V axials for $9.50 each from mouser, or spend the "big bucks" and replace them with actual Sprague Atoms at $21 each- but are yours actually bad?

The Collins guys say most times no.

The 30L-1 is collectible and sells for $500-$1200- I wouldn't put no name junk in it. If they are bad, I would spend the $126 and put the correct capacitors in it.


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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Sun 22, 2021 2:14 am 
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Regardless, in a big supply like that I would test even new caps. There are maybe two in a million bad? but that is better odds than alot of lotteries. Generally they put high value equalizing resistors across series wired filter caps in transmitters to equalize the voltage on them and also bleed off the HV when it is turned off. SO check those resistors too.

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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Sun 22, 2021 3:52 am 
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Location: Long Island NY
When putting capacitors in series in a piece of equipment, it really pays to match them up for leakage current (most important), capacitance (second most important), and ESR. New capacitors fresh out of the bag may test exactly the same for capacity but they often have different leakage and ESR. If put in series the one with the higher ESR will get hotter, and the one with the lowest leakage current will end up with more of the voltage across it Matching the caps assures you that you will get the best life out of them possible under the circumstances.

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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Tue 24, 2021 6:07 pm 
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Having a restored Tel-Ohmike TO-6A to hand, I reform all new electrolytic caps before installation... it takes very little time for the leakage current to drop below, say, 1 mA for typical P/S filter caps.
I used to reform used and NOS electrolytics, but gave that up a while back as a bad idea... new caps are cheap enough and we are restoring for the next 70 years!
Cheers,
Roger

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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Thu 26, 2021 9:51 pm 
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Just a little FYI BC likely stands for BC Components (Beyschlag Centralab components). According the the Vishay site BC emerged from Philips in 1999, and were acquired by Vishay in 2002. Aluminum electrolytic capacitors are according to Vishay branded with their name in addition to the BC name, so if the capacitors don't say Vishay BC on them they are likely approaching 20 years old. If they are to be put into service, I would put them into something less critical.



Source: https://www.vishay.com/company/brands/bccomponents/

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 Post subject: Re: Reform NOS Capacitors?
PostPosted: Aug Fri 27, 2021 9:03 am 
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I have an old Eico eye type cap checker with variable voltage to check caps with. I have used it numerous times to reform caps. I start at a low voltage and slowly raise it until the eye starts to show leakage, then back it down a bit. After some time, I go raise the voltage slowly, until I get the desired WV.

So far, after 40+ yrs. of doing it this way, I have had no problems.

I have also used one of the Sencore cap testers using the reform function on it.

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