John Larkin Massive Bullshitter wrote: --------------------------------------> > > > >> >** The actual leakage current with HV electros is normally in the micro-amp range so dissipation causes no discernible temp rise. Ambient temp and rises in same entirely swamp it. > >> > > >> >Where series bleeder resistors are used ( eg 100,000 Fender tube amplifiers ) they pass about 1mA which is enough to reduce and nearly eliminate mid point voltage offset. > >> > > >> >The main benefit however is in bleeding off charge so the caps do not present a hazard if the AC supply is removed while there is no load on the PSU. > >> > > >> >There are a couple of ways this can happen. > >> > > >> >See typical schem: > >> > > >> >https://schematicheaven.net/fenderamps/fender_bassman50.pdf > >> > > > > > > >** For an unexplained reason JL introduces a new topic here. > > > > Keeping the wacky guy on-topic is a battle. > > > > This is called a "discussion group." And isn't heat related to > electrolytic cap life? >** The use of fans is a new context, not related to my post above. Larkin might as well have snipped the lot.. It's an asshole thing to do and the loopy cunt does it constantly. Looks a whole lot like stalking. --------------------------------> > >Many tube scopes had fans fitted to the back panel and with a series dropping resistor could be made very quiet indeed. > > > >Some famous tube instrument amps had AC fans as standard, but there was a big nasty waiting to catch any designer who was stupid enough. > > > >Ampeg released a new version of their famous SVT, a 300W tube bass amp in the late 1990s. It had an AC fan that ran continuously. > > > >The designer made two bad errors: > > > >1. He made the air flow go under the chassis, over the main PCB with all the output tube sockets and up though holes to cool each 6550 tube's glass envelope. A similar method is used in high power RF transmitters. > > > >2. He also fitted octal sockets that had 2 inch long pins - so the PCB could be remain deep under the chassis with the socket's flange secured to the metal deck as usual. > > > >The result was that dust and fluff collected around all the long pins until a massive 700VDC arc-over occurred between an adjacent pair ( plate and heater ) causing extensive damage to the PCB, tubes and many other parts. > > > >Took hours to clean up and fix. > > > >Later production examples had plastic sleeving fitted to the long pins. > > > >The PCB still became so badly contaminated it was no cure. > > > > > > > >.... Phil > > > > It didn't help thermally that some audio gear was literally > upholstered. >** See - the crazy, stalking cunt does it again. No relevance to my carefully explained post, just another smartarses, unsupported snipe. Shows clearly how his ASD fucked brain works, or not. The direct opposite of having a "discussion". .... Phil
Film capacitor as power-supply filter
Started by ●October 7, 2019
Reply by ●October 14, 20192019-10-14
Reply by ●October 16, 20192019-10-16
On Monday, October 14, 2019 at 12:17:39 AM UTC-4, Bill Sloman wrote:> On Monday, October 14, 2019 at 2:13:58 PM UTC+11, m...@uga.edu wrote: > > The rest of the story... > > > > For those who tuned in late, I'm replacing the power supply filters in a Heathkit IT-11 capacitor checker. In the original circuit they are two 40-uF 350-V in series (to handle 600 V). I ordered a 20-uF 1-kV film capacitor to replace them. > > > > Well, there just isn't room for that film capacitor under this chassis! So I had to resort to two 47-uF 450-V in series, like Heathkit's original. > > > > There was debate in this thread about whether to add balancing resistors, and I didn't. John Larkin said "they take care of themselves." Indeed they do, sharing the voltage to within a few percent of equal. > > > > I wonder if Mr. Larkin could explain further. Is there some effect that makes them equalize if they have different leakages to start with? I would expect the opposite, that the leakier one would carry a lower voltage and would form less, causing the difference in leakage to increase -- but I might be wrong. > > Leakage currents have a tendency to increase exponentially with applied voltage, so you often don't need much voltage difference to compensate for significant differences in initial leakage current. > > Some manufacturer's application note that I read back in 1970 was a full bottle on the subject. > > <snip> > > -- > Bill Sloman, SydneyThey do no such thing. For aluminum ecaps the leakage is k x sqrt(CV), making the ratio of voltages proportional to C1/C2. That can be a pretty big disparity. My guess is the manufacturer makes some attempt at matching C before installation. But what does your incredibly incapable and super ignorant fuck nothing of a pedophiles tell you about it?
Reply by ●October 16, 20192019-10-16
On Wed, 16 Oct 2019 09:08:22 -0700 (PDT), bloggs.fredbloggs.fred@gmail.com wrote:>On Monday, October 14, 2019 at 12:17:39 AM UTC-4, Bill Sloman wrote: >> On Monday, October 14, 2019 at 2:13:58 PM UTC+11, m...@uga.edu wrote: >> > The rest of the story... >> > >> > For those who tuned in late, I'm replacing the power supply filters in a Heathkit IT-11 capacitor checker. In the original circuit they are two 40-uF 350-V in series (to handle 600 V). I ordered a 20-uF 1-kV film capacitor to replace them. >> > >> > Well, there just isn't room for that film capacitor under this chassis! So I had to resort to two 47-uF 450-V in series, like Heathkit's original. >> > >> > There was debate in this thread about whether to add balancing resistors, and I didn't. John Larkin said "they take care of themselves." Indeed they do, sharing the voltage to within a few percent of equal. >> > >> > I wonder if Mr. Larkin could explain further. Is there some effect that makes them equalize if they have different leakages to start with? I would expect the opposite, that the leakier one would carry a lower voltage and would form less, causing the difference in leakage to increase -- but I might be wrong. >> >> Leakage currents have a tendency to increase exponentially with applied voltage, so you often don't need much voltage difference to compensate for significant differences in initial leakage current. >> >> Some manufacturer's application note that I read back in 1970 was a full bottle on the subject. >> >> <snip> >> >> -- >> Bill Sloman, Sydney > >They do no such thing. For aluminum ecaps the leakage is k x sqrt(CV), making the ratio of voltages proportional to C1/C2. That can be a pretty big disparity. My guess is the manufacturer makes some attempt at matching C before installation.I think your equation is generic on leakage at rated voltage, across cap ratings. It implies a declining slope for a particular capacitor, which is not how they behave. Applied to single caps, it would make a series string unstable. It's surprising how rare I/V curves are for electrolytics, practically not to be found. https://tadiranbatteries.de/pdf/applications/leakage-current-properties-of-modern-electrolytic-capacitors.pdf Fig 7 looks like semi-serious data, but ends at rated voltage. In my experience, leakage increases radically above rated voltage. But even that curve implies series cap string voltage self-equalization.
Reply by ●October 16, 20192019-10-16
Some Loony hiding behind bloggs.fre...@gmail.com wrote: ------------------------------------------------> >> > > Leakage currents have a tendency to increase exponentially with > > applied voltage, so you often don't need much voltage difference > > to compensate for significant differences in initial leakage current. > > > > > They do no such thing.** Fraid they do.> For aluminum ecaps the leakage is k x sqrt(CV),** Fraid that is not the formula for ACTUAL electro cap leakage at all. One sees it sometimes on spec sheets describing the MAX leakage to be expected where "C" and "V" are the makers rated vales for a particular cap. This link give a bit more detail to an non-simple situation.> making the ratio of voltages proportional to C1/C2.** Absolute rubbish.> But what does your incredibly incapable and super ignorant > fuck nothing of a pedophiles tell you about it?** Kinda undoes any possibility of a sane post - don't it? .... Phil
Reply by ●October 16, 20192019-10-16
Phil Allison wrote: ------------------------> This link give a bit more detail to an non-simple situation.** Oops - see same link JL posted. .... Phil
Reply by ●October 16, 20192019-10-16
On Wed, 16 Oct 2019 15:03:19 -0700 (PDT), Phil Allison <pallison49@gmail.com> wrote:>Phil Allison wrote: > >------------------------ > > >> This link give a bit more detail to an non-simple situation. > > > ** Oops - see same link JL posted. > > > >.... PhilI might just measure a couple of electrolytic caps. I think the leakage jumps radically a bit past the reform voltage. Here's some data on some other caps. https://www.dropbox.com/s/dlet57gmlntxx9h/Ccap_Leakage.JPG?dl=0 https://www.dropbox.com/s/euxh4uzhoeft249/Polymer_Leakage.jpg?dl=0 https://www.dropbox.com/s/fq70y6vy854k8y8/Supercap_Leakage.JPG?dl=0 They all curve up! The polymer leakage data is entangled with its time behavior, sort of a reform or dielectric absorption thing. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●October 16, 20192019-10-16
On Wed, 16 Oct 2019 15:28:02 -0700, John Larkin <jlarkin@highland_atwork_technology.com> wrote:>On Wed, 16 Oct 2019 15:03:19 -0700 (PDT), Phil Allison ><pallison49@gmail.com> wrote: > >>Phil Allison wrote: >> >>------------------------ >> >> >>> This link give a bit more detail to an non-simple situation. >> >> >> ** Oops - see same link JL posted. >> >> >> >>.... Phil > >I might just measure a couple of electrolytic caps. I think the >leakage jumps radically a bit past the reform voltage. > >Here's some data on some other caps. > >https://www.dropbox.com/s/dlet57gmlntxx9h/Ccap_Leakage.JPG?dl=0 > >https://www.dropbox.com/s/euxh4uzhoeft249/Polymer_Leakage.jpg?dl=0 > >https://www.dropbox.com/s/fq70y6vy854k8y8/Supercap_Leakage.JPG?dl=0 > >They all curve up! The polymer leakage data is entangled with its time >behavior, sort of a reform or dielectric absorption thing.Here's possibly the only curve like this ever posted online: https://www.dropbox.com/s/i4wwttdgqycz9rv/Alum_Leakage_63u.JPG?raw=1 The data is crude, because there is reforming and dielectric absorption going on, and I don't have a month to play with this. But the curve is clearly radically upward. Not a zener, more like an MOV. The current is very noisy above maybe 70 volts. I see what looks like brief high current spikes. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●October 17, 20192019-10-17
John Larkin <jlarkin@highland_atwork_technology.com> wrote:> On Wed, 16 Oct 2019 09:08:22 -0700 (PDT),> It's surprising how rare I/V curves are for electrolytics, practically > not to be found.> https://tadiranbatteries.de/pdf/applications/leakage-current-properties-o > f-modern-electrolytic-capacitors.pdfI posted that link two days ago in my reply to Win on Mon, 07 Oct 2019. Here is my post: "When the capacitor is left with no supplied voltage, the film tends to dissociate and become thinner. Applying a voltage to the cap restores the film." "An excellent description is given in" "Leakage current properties of modern electrolytic capacitors" https://tadiranbatteries.de/pdf/applications/leakage-current-properties-of- modern-electrolytic-capacitors.pdf --------------------------------------------------------------------------- Also see https://jianghai-europe.com/wp-content/uploads/8-Jianghai-Europe-E-Cap- Leakage-Current-AAL-2018-09-18.pdf This paper has lots of good information, such as fig. 4, leakage as a function of time, voltage and temperature. This precedes your later post showing leakage as a function of voltage. The leakage is exponential. It also includes information on using resistors to balance the voltages in series capacitors. One point that has not been discussed so far is the paper mentions the balancing resistors will discharge the electrolytics quickly when power is removed. This is an important safety factor in the case of very low leakage capacitors. There is a huge amount of information on electrolytic capacitors on the web. For example, see Cornell Dublier, "Aluminum Electrolytic Capacitor Application Guide" at http://www.cde.com/resources/catalogs/AEappGUIDE.pdf Also see Rubycon, at http://rubycon.co.jp/en/products/alumi/pdf/Performances.pdf and so on.
Reply by ●October 17, 20192019-10-17
Steve Wilson wrote: ------------------> Also see > > https://jianghai-europe.com/wp-content/uploads/8-Jianghai-Europe-E-Cap- > Leakage-Current-AAL-2018-09-18.pdf > > This paper has lots of good information, such as fig. 4, leakage as a > function of time, voltage and temperature. This precedes your later post > showing leakage as a function of voltage. The leakage is exponential. >** Fig 4 is next to useless. Presents only the barest nominal, virtuual data.> > One point that has not been discussed so far is the paper mentions the > balancing resistors will discharge the electrolytics quickly when power is > removed. >** That tiny we comment is hard to find. And you missed this post from me here two days ago ------------------------------------------------------------------- ** The actual leakage current with HV electros is normally in the micro-amp range so dissipation causes no discernible temp rise. Ambient temp and rises in same entirely swamp it. Where series bleeder resistors are used ( eg 100,000 Fender tube amplifiers ) they pass about 1mA which is enough to reduce and nearly eliminate mid point voltage offset. The main benefit however is in bleeding off charge so the caps do not present a hazard if the AC supply is removed while there is no load on the PSU. There are a couple of ways this can happen. See typical schem: https://schematicheaven.net/fenderamps/fender_bassman50.pdf ---------------------------------------------------------------------- ** Yawwnnnn ..... ..... Phil
Reply by ●October 17, 20192019-10-17
John Larkin <jlarkin@highland_atwork_technology.com> wrote:> Here's possibly the only curve like this ever posted online:> https://www.dropbox.com/s/i4wwttdgqycz9rv/Alum_Leakage_63u.JPG?raw=1See Fig. 4(b) on Page 2 in https://jianghai-europe.com/wp-content/uploads/8-Jianghai-Europe-E-Cap- Leakage-Current-AAL-2018-09-18.pdf The curves are exponential.
