Gentlemen, An app note I was referred to recently (Nichicon source IIRC) stated that even new electrolytic caps should have their oxide layer reformed before being put into service if they've been on the shelf for as little as 12 months. They suggested doing this by charging them to 90% of max stated voltage via a 1k resistor and leaving them fully charged for 30 minutes. thereafter. This gives the oxide layer a chance to reform, they say. It's actually quite a rapid charge in most cases and certainl much faster than we would use for bringing vintage/NOS caps back to a serviceable condition. But for convenience you can't beat it. Anyway, cut a long story short. Previously I've brought old test gear back to life by manually bringing the supply voltage up via a variac and monitoring the current for any 'abberent behaviour' which is rather time consuming. In future I think I'll just use a 10k say resistor in the hot wire and leave it to its own devices, plugged in and switched on for 12 hours. That should be suitably kind to vintage equipment. But then I thought - would this still work if the equipment in question had an SMPS? It's fine for linear PSUs, but SMPS? Anyone care to offer an informed opinion? CD.
SMPS Behaviour at low supply voltages
Started by ●September 10, 2023
Reply by ●September 10, 20232023-09-10
On Sunday, September 10, 2023 at 5:25:22 AM UTC-4, Cursitor Doom wrote:> Gentlemen, > > An app note I was referred to recently (Nichicon source IIRC) stated > that even new electrolytic caps should have their oxide layer reformed > before being put into service if they've been on the shelf for as > little as 12 months. They suggested doing this by charging them to 90% > of max stated voltage via a 1k resistor and leaving them fully charged > for 30 minutes. thereafter. This gives the oxide layer a chance to > reform, they say. It's actually quite a rapid charge in most cases and > certainl much faster than we would use for bringing vintage/NOS caps > back to a serviceable condition. But for convenience you can't beat > it. Anyway, cut a long story short. Previously I've brought old test > gear back to life by manually bringing the supply voltage up via a > variac and monitoring the current for any 'abberent behaviour' which > is rather time consuming. In future I think I'll just use a 10k say > resistor in the hot wire and leave it to its own devices, plugged in > and switched on for 12 hours. That should be suitably kind to vintage > equipment. But then I thought - would this still work if the equipment > in question had an SMPS? It's fine for linear PSUs, but SMPS? Anyone > care to offer an informed opinion? > > CD.Nichicon specializes in very low leakage e-caps mainly intended for timing. Their reforming procedure is for testing/ quality control purposes, and not intended for general applications for which it is mostly inapplicable. See the section on reforming: https://www.tdk-electronics.tdk.com/download/185386/e724fb43668a157bc547c65b0cff75f8/pdf-generaltechnicalinformation.pdf
Reply by ●September 10, 20232023-09-10
On Sun, 10 Sep 2023 10:25:13 +0100, Cursitor Doom <cd@notformail.com> wrote:>Gentlemen, > >An app note I was referred to recently (Nichicon source IIRC) stated >that even new electrolytic caps should have their oxide layer reformed >before being put into service if they've been on the shelf for as >little as 12 months. They suggested doing this by charging them to 90% >of max stated voltage via a 1k resistor and leaving them fully charged >for 30 minutes. thereafter.We don't do that in production, and we surely have caps in stock that are several years old. I think elec caps are much better than they used to be. This gives the oxide layer a chance to>reform, they say. It's actually quite a rapid charge in most cases and >certainl much faster than we would use for bringing vintage/NOS caps >back to a serviceable condition. But for convenience you can't beat >it. Anyway, cut a long story short. Previously I've brought old test >gear back to life by manually bringing the supply voltage up via a >variac and monitoring the current for any 'abberent behaviour' which >is rather time consuming. In future I think I'll just use a 10k say >resistor in the hot wire and leave it to its own devices, plugged in >and switched on for 12 hours. That should be suitably kind to vintage >equipment. But then I thought - would this still work if the equipment >in question had an SMPS? It's fine for linear PSUs, but SMPS? Anyone >care to offer an informed opinion? > >CD.We don't do that in production, and we surely have caps that are several years old. I think elec caps are much better than they used to be.
Reply by ●September 10, 20232023-09-10
On Sunday, September 10, 2023 at 10:55:18 AM UTC-4, John Larkin wrote:> On Sun, 10 Sep 2023 10:25:13 +0100, Cursitor Doom <c...@notformail.com> > wrote: > >Gentlemen, > > > >An app note I was referred to recently (Nichicon source IIRC) stated > >that even new electrolytic caps should have their oxide layer reformed > >before being put into service if they've been on the shelf for as > >little as 12 months. They suggested doing this by charging them to 90% > >of max stated voltage via a 1k resistor and leaving them fully charged > >for 30 minutes. thereafter. > We don't do that in production, and we surely have caps in stock that > are several years old. I think elec caps are much better than they > used to be. > This gives the oxide layer a chance to > >reform, they say. It's actually quite a rapid charge in most cases and > >certainl much faster than we would use for bringing vintage/NOS caps > >back to a serviceable condition. But for convenience you can't beat > >it. Anyway, cut a long story short. Previously I've brought old test > >gear back to life by manually bringing the supply voltage up via a > >variac and monitoring the current for any 'abberent behaviour' which > >is rather time consuming. In future I think I'll just use a 10k say > >resistor in the hot wire and leave it to its own devices, plugged in > >and switched on for 12 hours. That should be suitably kind to vintage > >equipment. But then I thought - would this still work if the equipment > >in question had an SMPS? It's fine for linear PSUs, but SMPS? Anyone > >care to offer an informed opinion? > > > >CD. > We don't do that in production, and we surely have caps that are > several years old. I think elec caps are much better than they used to > be.I always wondered what that 30 second overvoltage rating was all about, then I powered up a largely vacuum tube product and watched that voltage zoom into overvoltage until the filaments heated up and pulled the old fashioned regulator output to operating voltage.
Reply by ●September 10, 20232023-09-10
On Sun, 10 Sep 2023 08:08:31 -0700 (PDT), Fred Bloggs <bloggs.fredbloggs.fred@gmail.com> wrote:>On Sunday, September 10, 2023 at 10:55:18?AM UTC-4, John Larkin wrote: >> On Sun, 10 Sep 2023 10:25:13 +0100, Cursitor Doom <c...@notformail.com> >> wrote: >> >Gentlemen, >> > >> >An app note I was referred to recently (Nichicon source IIRC) stated >> >that even new electrolytic caps should have their oxide layer reformed >> >before being put into service if they've been on the shelf for as >> >little as 12 months. They suggested doing this by charging them to 90% >> >of max stated voltage via a 1k resistor and leaving them fully charged >> >for 30 minutes. thereafter. >> We don't do that in production, and we surely have caps in stock that >> are several years old. I think elec caps are much better than they >> used to be. >> This gives the oxide layer a chance to >> >reform, they say. It's actually quite a rapid charge in most cases and >> >certainl much faster than we would use for bringing vintage/NOS caps >> >back to a serviceable condition. But for convenience you can't beat >> >it. Anyway, cut a long story short. Previously I've brought old test >> >gear back to life by manually bringing the supply voltage up via a >> >variac and monitoring the current for any 'abberent behaviour' which >> >is rather time consuming. In future I think I'll just use a 10k say >> >resistor in the hot wire and leave it to its own devices, plugged in >> >and switched on for 12 hours. That should be suitably kind to vintage >> >equipment. But then I thought - would this still work if the equipment >> >in question had an SMPS? It's fine for linear PSUs, but SMPS? Anyone >> >care to offer an informed opinion? >> > >> >CD. >> We don't do that in production, and we surely have caps that are >> several years old. I think elec caps are much better than they used to >> be. > >I always wondered what that 30 second overvoltage rating was all about, then I powered up a largely vacuum tube product and watched that voltage zoom into overvoltage until the filaments heated up and pulled the old fashioned regulator output to operating voltage.I'm afraid neither you nor John (undoubtedly august personages that you are) have actually answered the question....
Reply by ●September 10, 20232023-09-10
On Sun, 10 Sep 2023 10:25:13 +0100, Cursitor Doom <cd@notformail.com> wrote:>Gentlemen, > >An app note I was referred to recently (Nichicon source IIRC) stated >that even new electrolytic caps should have their oxide layer reformed >before being put into service if they've been on the shelf for as >little as 12 months. They suggested doing this by charging them to 90% >of max stated voltage via a 1k resistor and leaving them fully charged >for 30 minutes. thereafter. This gives the oxide layer a chance to >reform, they say. It's actually quite a rapid charge in most cases and >certainl much faster than we would use for bringing vintage/NOS caps >back to a serviceable condition. But for convenience you can't beat >it. Anyway, cut a long story short. Previously I've brought old test >gear back to life by manually bringing the supply voltage up via a >variac and monitoring the current for any 'abberent behaviour' which >is rather time consuming. In future I think I'll just use a 10k say >resistor in the hot wire and leave it to its own devices, plugged in >and switched on for 12 hours. That should be suitably kind to vintage >equipment. But then I thought - would this still work if the equipment >in question had an SMPS? It's fine for linear PSUs, but SMPS? Anyone >care to offer an informed opinion? > >CD.You can refer to MIL-HDBK-1131 for electrolytic cap storage and reformation recommendations. They suggest limiting current to 5mA, below the rated voltage of the part, as the control during reforming. RL
Reply by ●September 10, 20232023-09-10
On 10/09/2023 16:31, Cursitor Doom wrote:> On Sun, 10 Sep 2023 08:08:31 -0700 (PDT), Fred Bloggs > <bloggs.fredbloggs.fred@gmail.com> wrote: > >> On Sunday, September 10, 2023 at 10:55:18?AM UTC-4, John Larkin wrote: >>> On Sun, 10 Sep 2023 10:25:13 +0100, Cursitor Doom <c...@notformail.com> >>> wrote: >>>> Gentlemen, >>>> >>>> An app note I was referred to recently (Nichicon source IIRC) stated >>>> that even new electrolytic caps should have their oxide layer reformed >>>> before being put into service if they've been on the shelf for as >>>> little as 12 months. They suggested doing this by charging them to 90% >>>> of max stated voltage via a 1k resistor and leaving them fully charged >>>> for 30 minutes. thereafter. >>> We don't do that in production, and we surely have caps in stock that >>> are several years old. I think elec caps are much better than they >>> used to be. >>> This gives the oxide layer a chance to >>>> reform, they say. It's actually quite a rapid charge in most cases and >>>> certainl much faster than we would use for bringing vintage/NOS caps >>>> back to a serviceable condition. But for convenience you can't beat >>>> it. Anyway, cut a long story short. Previously I've brought old test >>>> gear back to life by manually bringing the supply voltage up via a >>>> variac and monitoring the current for any 'abberent behaviour' which >>>> is rather time consuming. In future I think I'll just use a 10k say >>>> resistor in the hot wire and leave it to its own devices, plugged in >>>> and switched on for 12 hours. That should be suitably kind to vintage >>>> equipment. But then I thought - would this still work if the equipment >>>> in question had an SMPS? It's fine for linear PSUs, but SMPS? Anyone >>>> care to offer an informed opinion? >>>> >>>> CD. >>> We don't do that in production, and we surely have caps that are >>> several years old. I think elec caps are much better than they used to >>> be. >> >> I always wondered what that 30 second overvoltage rating was all about, then I powered up a largely vacuum tube product and watched that voltage zoom into overvoltage until the filaments heated up and pulled the old fashioned regulator output to operating voltage. > > I'm afraid neither you nor John (undoubtedly august personages that > you are) have actually answered the question....Isn't the app note talking about reforming individual capacitors? In a completed piece of equipment you'd need to do that to each capacitor. Possibly even having to unsolder at least one lead. Imagine an electrolytic bypassing a low value emitter resistor in an amplifier - a 10K resistor there would have no chance against that in-circuit load. If you mean putting 10k in series with the mains supply then the short answer is NO. The first capacitor after the rectifier may see a little voltage but I doubt the supply would startup and certainly no other downstream capacitors would get reformed. piglet
Reply by ●September 10, 20232023-09-10
On Sun, 10 Sep 2023 17:28:50 +0100, piglet <erichpwagner@hotmail.com> wrote:>On 10/09/2023 16:31, Cursitor Doom wrote: >> On Sun, 10 Sep 2023 08:08:31 -0700 (PDT), Fred Bloggs >> <bloggs.fredbloggs.fred@gmail.com> wrote: >> >>> On Sunday, September 10, 2023 at 10:55:18?AM UTC-4, John Larkin wrote: >>>> On Sun, 10 Sep 2023 10:25:13 +0100, Cursitor Doom <c...@notformail.com> >>>> wrote: >>>>> Gentlemen, >>>>> >>>>> An app note I was referred to recently (Nichicon source IIRC) stated >>>>> that even new electrolytic caps should have their oxide layer reformed >>>>> before being put into service if they've been on the shelf for as >>>>> little as 12 months. They suggested doing this by charging them to 90% >>>>> of max stated voltage via a 1k resistor and leaving them fully charged >>>>> for 30 minutes. thereafter. >>>> We don't do that in production, and we surely have caps in stock that >>>> are several years old. I think elec caps are much better than they >>>> used to be. >>>> This gives the oxide layer a chance to >>>>> reform, they say. It's actually quite a rapid charge in most cases and >>>>> certainl much faster than we would use for bringing vintage/NOS caps >>>>> back to a serviceable condition. But for convenience you can't beat >>>>> it. Anyway, cut a long story short. Previously I've brought old test >>>>> gear back to life by manually bringing the supply voltage up via a >>>>> variac and monitoring the current for any 'abberent behaviour' which >>>>> is rather time consuming. In future I think I'll just use a 10k say >>>>> resistor in the hot wire and leave it to its own devices, plugged in >>>>> and switched on for 12 hours. That should be suitably kind to vintage >>>>> equipment. But then I thought - would this still work if the equipment >>>>> in question had an SMPS? It's fine for linear PSUs, but SMPS? Anyone >>>>> care to offer an informed opinion? >>>>> >>>>> CD. >>>> We don't do that in production, and we surely have caps that are >>>> several years old. I think elec caps are much better than they used to >>>> be. >>> >>> I always wondered what that 30 second overvoltage rating was all about, then I powered up a largely vacuum tube product and watched that voltage zoom into overvoltage until the filaments heated up and pulled the old fashioned regulator output to operating voltage. >> >> I'm afraid neither you nor John (undoubtedly august personages that >> you are) have actually answered the question.... > >Isn't the app note talking about reforming individual capacitors?Yes.> In a >completed piece of equipment you'd need to do that to each capacitor. >Possibly even having to unsolder at least one lead. Imagine an >electrolytic bypassing a low value emitter resistor in an amplifier - a >10K resistor there would have no chance against that in-circuit load. > >If you mean putting 10k in series with the mains supply then the short >answer is NO. The first capacitor after the rectifier may see a little >voltage but I doubt the supply would startup and certainly no other >downstream capacitors would get reformed. > >piglet >Oh bugger. I hadn't thought of that.Thanks, Piglet.
Reply by ●September 10, 20232023-09-10
On Sun, 10 Sep 2023 16:31:59 +0100, Cursitor Doom <cd@notformail.com> wrote:>On Sun, 10 Sep 2023 08:08:31 -0700 (PDT), Fred Bloggs ><bloggs.fredbloggs.fred@gmail.com> wrote: > >>On Sunday, September 10, 2023 at 10:55:18?AM UTC-4, John Larkin wrote: >>> On Sun, 10 Sep 2023 10:25:13 +0100, Cursitor Doom <c...@notformail.com> >>> wrote: >>> >Gentlemen, >>> > >>> >An app note I was referred to recently (Nichicon source IIRC) stated >>> >that even new electrolytic caps should have their oxide layer reformed >>> >before being put into service if they've been on the shelf for as >>> >little as 12 months. They suggested doing this by charging them to 90% >>> >of max stated voltage via a 1k resistor and leaving them fully charged >>> >for 30 minutes. thereafter. >>> We don't do that in production, and we surely have caps in stock that >>> are several years old. I think elec caps are much better than they >>> used to be. >>> This gives the oxide layer a chance to >>> >reform, they say. It's actually quite a rapid charge in most cases and >>> >certainl much faster than we would use for bringing vintage/NOS caps >>> >back to a serviceable condition. But for convenience you can't beat >>> >it. Anyway, cut a long story short. Previously I've brought old test >>> >gear back to life by manually bringing the supply voltage up via a >>> >variac and monitoring the current for any 'abberent behaviour' which >>> >is rather time consuming. In future I think I'll just use a 10k say >>> >resistor in the hot wire and leave it to its own devices, plugged in >>> >and switched on for 12 hours. That should be suitably kind to vintage >>> >equipment. But then I thought - would this still work if the equipment >>> >in question had an SMPS? It's fine for linear PSUs, but SMPS? Anyone >>> >care to offer an informed opinion? >>> > >>> >CD. >>> We don't do that in production, and we surely have caps that are >>> several years old. I think elec caps are much better than they used to >>> be. >> >>I always wondered what that 30 second overvoltage rating was all about, then I powered up a largely vacuum tube product and watched that voltage zoom into overvoltage until the filaments heated up and pulled the old fashioned regulator output to operating voltage. > >I'm afraid neither you nor John (undoubtedly august personages that >you are) have actually answered the question....Demand a refund!
Reply by ●September 10, 20232023-09-10
On Sun, 10 Sep 2023 11:01:01 -0700, John Larkin <jjlarkin@highlandtechnology.com> wrote:>On Sun, 10 Sep 2023 16:31:59 +0100, Cursitor Doom <cd@notformail.com> >wrote: > >>On Sun, 10 Sep 2023 08:08:31 -0700 (PDT), Fred Bloggs >><bloggs.fredbloggs.fred@gmail.com> wrote: >> >>>On Sunday, September 10, 2023 at 10:55:18?AM UTC-4, John Larkin wrote: >>>> On Sun, 10 Sep 2023 10:25:13 +0100, Cursitor Doom <c...@notformail.com> >>>> wrote: >>>> >Gentlemen, >>>> > >>>> >An app note I was referred to recently (Nichicon source IIRC) stated >>>> >that even new electrolytic caps should have their oxide layer reformed >>>> >before being put into service if they've been on the shelf for as >>>> >little as 12 months. They suggested doing this by charging them to 90% >>>> >of max stated voltage via a 1k resistor and leaving them fully charged >>>> >for 30 minutes. thereafter. >>>> We don't do that in production, and we surely have caps in stock that >>>> are several years old. I think elec caps are much better than they >>>> used to be. >>>> This gives the oxide layer a chance to >>>> >reform, they say. It's actually quite a rapid charge in most cases and >>>> >certainl much faster than we would use for bringing vintage/NOS caps >>>> >back to a serviceable condition. But for convenience you can't beat >>>> >it. Anyway, cut a long story short. Previously I've brought old test >>>> >gear back to life by manually bringing the supply voltage up via a >>>> >variac and monitoring the current for any 'abberent behaviour' which >>>> >is rather time consuming. In future I think I'll just use a 10k say >>>> >resistor in the hot wire and leave it to its own devices, plugged in >>>> >and switched on for 12 hours. That should be suitably kind to vintage >>>> >equipment. But then I thought - would this still work if the equipment >>>> >in question had an SMPS? It's fine for linear PSUs, but SMPS? Anyone >>>> >care to offer an informed opinion? >>>> > >>>> >CD. >>>> We don't do that in production, and we surely have caps that are >>>> several years old. I think elec caps are much better than they used to >>>> be. >>> >>>I always wondered what that 30 second overvoltage rating was all about, then I powered up a largely vacuum tube product and watched that voltage zoom into overvoltage until the filaments heated up and pulled the old fashioned regulator output to operating voltage. >> >>I'm afraid neither you nor John (undoubtedly august personages that >>you are) have actually answered the question.... > >Demand a refund!Good idea. The Larkin's advice is worth exactly what you paid for it.
