Electrolytic Caps [Good or Bad?]

[mdxeng]

If they're not physically or thermally abused and not overloaded with voltage, they should last a very long time. Lot's of old gear have good coupling caps with this type of construction.

[guitician]

I started looking for "Long Life" caps and found solid polymer caps with as much as 63,000 hours life at 75 degrees Celsius or 167 degrees Fahrenheit. That's 28 years running six hours a day. It didn't see voltages above 63vdc though.

[mdxeng]

The basic thing to remember is that the power supply filter caps, especially the first stage that feeds the output transformer center-tap which 99% of the time are electrolytics, are the ones that work the hardest and the ones that typically need replacing before anything else. The coupling caps that are in the signal flow path don't work nearly as hard and are usually film-type which last very long (but sometimes go bad and are a little difficult to diagnose). So, first step is understand which part of the amp your looking at replacing/upgrading and consider how hard the cap is working. The first stage filter cap in a 50W guitar amp typical values: 450VDC, 70mA @idle, 100-150mA when pushed (rock/metal,etc), typical ripple @idle 2-4VAC. When you see the ripple voltage go up as the amp ages or (approx.) >4VAC @idle, then this may be a sign of an issue. Always look at the filter caps during a service and look for what has been already talked about in this thread. Coupling caps have high voltages, but current levels are small (<1mA) so they are not being worked like the filter caps that are feeding the power tubes with current so the amp sounds good, crisp, loud and nice.

You can hear bad electrolytics. Lack of bass response or audible 60Hz hum are symptoms. Popping sounds, stuff leaking from the chassis, debris inside the chassis like something exploded - these are more obvious symptoms(!).

I've used non-electrolytics (Solen 630V metallized poly) in filter cap positions and I expect they'll last a long time. Sprague Atoms are very reliable for electrolytics, but performance may not be what you're looking for.

[Steve Conner]

So, what's the life expectancy of a PIO(Paper-in-Oil) type of filter cap? They are soldered in a can, so they dont dry out. They may age in different ways though.

I've seen paper-in-oil caps go leaky (of current, that is, not oil!) and metallized paper ones too. I just replace them with modern plastic film types.

You really don't want me to service your 1948 TV front Pro.

[tedmich]

I've seen paper-in-oil caps go leaky (of current, that is, not oil!) and metallized paper ones too. I just replace them with modern plastic film types.

You really don't want me to service your 1948 TV front Pro.

the association of PIO caps with massive PCB pollution is enough for me to completely avoid them. No audio qualities counterbalance their environmental impact, as they are commonly disposed of improperly. Of course the Mfg were the worst offenders, like GE releasing >500 tons into the Hudson River from their two capacitor manufacturing plants at Hudson Falls and Fort Edward, or Westinghouse in Indiana, or who knows what Soviet era factories today...

I've heard grizzled old techs mutter about how they haven't observed any increased cancer rates but that bad karma has to go somewhere...

[R.G.]

RG: I might be a genius but you sir, are a politician

Sir! I am not a member of the government or any other criminal organization!

So, what's the life expectancy of a PIO(Paper-in-Oil) type of filter cap? They are soldered in a can, so they dont dry out. They may age in different ways though.

Paper-in-oil is not the way to go. You want polypropylene-in-oil. I have an old textbook on "power capacitors", these being the only caps they could make back in telegraph days, and on into the 1950s. Paper was used because it was the only consistent insulating film they could get before plastics. Oil was used because it made the paper last longer and withstand a higher voltage.

The oil was originally mineral oil, later petroleum oils. Such capacitors were a distinct fire hazard, as one of their uses was in line balancing and power factor correction in power stations, and the bigger ones got... HOT. Sometimes they'd boil the oil, or be ruptured by a discharge, and spray hot, atomized oil into the air, producing a fuel-air explosion that might knock down the building. If not, it would burn it down. Special synthetic transformer oils were invented to sidestep the real danger of fire or explosion.

Your oil-and-paper caps would not be that big. However, the power cap industry went to polypropylene film with paper and finally polypro only as soon as it was technically feasible. Paper was never a great insulator. It was impossible in practice to produce paper free of conductive imperfections in some places. As a result, even the best paper had to be used in a dual layer, as the odds of two of these randomly spaced imperfections matching up was incredibly low. Polypropylene films can be made with zero conductive imperfections, so they went to paper plus polypro, then polypro entirely. Modern PCB-free caps are metalized polypropylene film in a non-pcb oil to dissipate heat.

the association of PIO caps with massive PCB pollution is enough for me to completely avoid them. No audio qualities counterbalance their environmental impact, as they are commonly disposed of improperly. Of course the Mfg were the worst offenders, like GE releasing >500 tons into the Hudson River from their two capacitor manufacturing plants at Hudson Falls and Fort Edward, or Westinghouse in Indiana, or who knows what Soviet era factories today...

I've heard grizzled old techs mutter about how they haven't observed any increased cancer rates but that bad karma has to go somewhere...

It's politically correct these days to assume that any oil-bearing capacitor is stuffed with PCBs and dioxin, and that companies like GE were trying to find ways to make the entire planet uninhabitable.

In fact, as I mentioned, PCB bearing insulating oils were developed to try to prevent power station workers and office workers where there were small power plants from being killed by explosion and fires. The guys who invented and used this stuff weren't sadistically evil - at first at least. They honestly could not, for instance, detect dioxin in parts per billion back in the 1950s. Nor was their objective to poison people - PCB build up to toxicity takes a while to happen and it's hard to track it back. PCB oils were so good for what they were intended for, there was an entire industry built up with billions of dollars (back when that was worth more than a casual sneeze) of industrial base, and very little in the way of alternatives when the toxicity was tracked down and analyzed sufficiently.

When they were nailed down, yep, there was some corporate greed to get over, but PCBs were pretty quickly banned, and *every single cap containing insulating oil* since the banning contains oil free of PCBs and dioxins. Guilt by association is always a tricky thing, and it's not much good for caps either. Modern manufacture oil bearing caps are as non-toxic as we can determine any such thing to be, and they're watched well because of the PCB issues.

The basic thing to remember is that the power supply filter caps, especially the first stage that feeds the output transformer center-tap which 99% of the time are electrolytics, are the ones that work the hardest and the ones that typically need replacing before anything else.

"Worked the hardest" is equivalent to "carries the highest ripple current, and is most heated by ripple current and other hot things nearby". Often that's a rectifier tube.

The coupling caps that are in the signal flow path don't work nearly as hard and are usually film-type which last very long

These things have the advantage of being film construction. This is much more heat-capable than electro caps, and don't have a built-in wear out mechanism like electros. Film caps may be ignored for any kind of regular replacement; replace them when they die.

In fact, no EE worth his salt will use an electro when there is a film which is modestly capable of doing the job. Electros would not exist if anything else could give us the CV product that electros do.

I've used non-electrolytics (Solen 630V metallized poly) in filter cap positions and I expect they'll last a long time.

I've been exhorting people to use motor-run caps for power filter caps for a long time. They have become relatively cheap ($1/uF at 450-500Vdc) and are designed to have huge ripple currents run through them and to dissipate the heat; and they don't have the wear-out mechanism of electros. This is part of my "Immortal Amplifier" that I've been preaching for years. In fact, they do work, and in fact they do last a long time. I rigged up my first amp like this over ten years ago. It's been too short a time to tell much, but ripple and temp rise are exactly what they were when the amp was new. I expect that the amp will work long after I'm dead if tubes can be had for it.

[tedmich]

It's politically correct these days to assume that any oil-bearing capacitor is stuffed with PCBs and dioxin, and that companies like GE were trying to find ways to make the entire planet uninhabitable.

In fact, as I mentioned, PCB bearing insulating oils were developed to try to prevent power station workers and office workers where there were small power plants from being killed by explosion and fires. The guys who invented and used this stuff weren't sadistically evil - at first at least. They honestly could not, for instance, detect dioxin in parts per billion back in the 1950s. Nor was their objective to poison people - PCB build up to toxicity takes a while to happen and it's hard to track it back. PCB oils were so good for what they were intended for, there was an entire industry built up with billions of dollars (back when that was worth more than a casual sneeze) of industrial base, and very little in the way of alternatives when the toxicity was tracked down and analyzed sufficiently.

When they were nailed down, yep, there was some corporate greed to get over, but PCBs were pretty quickly banned, and *every single cap containing insulating oil* since the banning contains oil free of PCBs and dioxins. Guilt by association is always a tricky thing, and it's not much good for caps either. Modern manufacture oil bearing caps are as non-toxic as we can determine any such thing to be, and they're watched well because of the PCB issues


I've been exhorting people to use motor-run caps for power filter caps for a long time. .

The incredible biological persistence of PCBs is why we can still be pissed about the tons GE dumped in NY and Westinghouse dumped in IN. The 1979 ban simply banned US production (after 600,000 tons) but they can still be used in "closed" systems (transformers and capacitors) and there is no plan to actually dispose of the ~1M tons produced until 2025, which is contingent on the so called POPs Treaty ratified by 105 countries....except the US!

Speaking as a biochemist, the health effects of the 200 odd PCB compounds are very scary. They worked well but ideally we shouldn't have to see their environmental impact for the next couple centuries because of some very real corporate dishonesty and greed. See this time line for details:
The History of PCBs - When Were Problems Detected

"quickly banned"? hardly as health effects were seen decades before "ban" and they are still all around us...

And as to GE's contempt for the planet, have you watched Conan O'Brien lately?

Oh yes motor start caps are DIRT cheap check these:
50 lot of 20uf for <$20
LOT OF 50 MOTOR START CAPACITORS CBB60 SH 20uF 240VAC - eBay (item 150380267658 end time Oct-20-09 16:11:27 PDT)

[Steve Conner]

Watch out! Motor start and motor run caps are two different things.

Motor start caps are often non-polar electrolytics, not rated for continuous running. I've exploded them before by running a capacitor-start motor off a variac, and I can tell you they smell pretty bad.

Motor RUN caps are great for using in tube amp power supplies, if you have the space in your chassis: they're much bigger than an electrolytic with the same CV product. But as RG says they'll surely outlive the amp builder, if not civilization itself. Wouldn't that be cool, if future archaeologists found your amp in a basement in the radioactive ruins of post-holocaust Manhattan, plugged it in, and it worked

[R.G.]

The incredible biological persistence of PCBs is why we can still be pissed about the tons GE dumped in NY and Westinghouse dumped in IN.

Actually, one can be pissed about almost anything. It's even better if it's a moral outrage, as that keeps the pissing going for long periods of time.

But that's neither here nor there. Cool. If you want to be angry about it and not use small paper and (different) oil capacitors for that reason, that's fine. I don't use small paper and oil caps because there are better, smaller, higher performance alternatives. In either case, neither you nor I use oil and paper caps.

The 1979 ban simply banned US production (after 600,000 tons)

I believe there are disposal requirements which make it almost impossible to dispose of them responsibly as well, some of which are draconian. These have the effect of making people look for ways to dispose of them improperly.

but they can still be used in "closed" systems (transformers and capacitors)

I think that's because of the "no good alternative" thing. I could be wrong, because I don't follow this in detail, but when you heat 50 or 100 gallons of oil inside a high voltage electrical assembly, fire and explosion is a possibility if the container ruptures. Of course, they are "closed" systems. We - and the "good" countries, too, like former Soviet bloc countries, Japan, China, Germany, France, the UK, etc. - also allow the use of enriched uranium in nuclear reactors, which are "closed" systems, encasing stuff more deadly than PCBs.

It's almost like humans can't be trusted with anything more dangerous than cowplop, isn't it?

and there is no plan to actually dispose of the ~1M tons produced until 2025, which is contingent on the so called POPs Treaty ratified by 105 countries....except the US!

Yep, we are the bad guys, all right.

It's funny - there are simple, direct ways to get people to do the right thing. For instance, we have a setup where anyone who is accidentally or otherwise in possession of a PCB bearing capacitor becomes in effect an eco-criminal. This is an incentive to just quietly get rid of the stuff and not be associated with it. Down the drain or dumped in the swamps comes easily to mind, and that's where a lot of the improper disposal comes from. Or we can use waste disposal "companies" that are the commercial arm of organized crime. They have some unusual ideas about how to properly dispose of stuff in general.

I sometimes come up with what I call engineering solutions to social problems. I think that if we took a different approach we could clean up PCBs, with the *help* of the corporate robber barons.

You want to gather up the PCBs for proper disposal? Buy it. Make the price such that people will TRY to find PCB-bearing stuff to turn it in. We have some precedence. The rise in the price of copper to a status as a minor precious metal has created a cottage industry for "copper finders". This involves things like tearing brass kick plates off doors, stripping out the ground wires on electrical poles, etc. If you paid an attractive price for PCB transformer oil, you could buy it up and properly high-temperature incinerate it under controlled conditions like we do with used, worn out currency. This would ensure that the PCBs are sought out with all the ingenuity that humans can come up with. In fact, big corporations would come up with ways to recapture the PCBs that escaped into the environment.

Too much money? Maybe not. We just got "given" a stimulus package which will largely be spent sometime during the next election year (which is neither here nor there - but it makes me angry that I can't be stimulated now when I need it) and which triples the national debt. Wouldn't it make good eco-sense to use some smallish fraction of that to clean up the Spawn-of-the-Devil PCBs that infest our environment? What price clean air and water? A few *billions*, which are down in the rounding error for the stimulus package would buy up all the PCBs and build the high temp incinerators, and make a big start to cleaning up the issue so we could get over it.

But we won't do that. That would reward positive, contributive behavior.

They worked well

They did that.

but ideally

Yep. Sigh. There's a shortage of ideal-ity these days.

we shouldn't have to see their environmental impact for the next couple centuries because of some very real corporate dishonesty and greed.

Yeah. If only we could keep people who are greedy from getting into positions of power to direct organizations... then we could make some progress!!

But seriously - think about what we could do by incenting good behavior.

Oh yes motor start caps are DIRT cheap check these:
50 lot of 20uf for <$20

As Steve notes, motor start caps are not the ticket. These are usually NP electrolytics, and are intended for intermittent use only when the motor starts and then are switched out by a centrifugal switch. They are a very bad alternative to normal electros in DC rectification. Motor run caps are designed for the motor to run with them hooked up all the time.

Sorry. I'm have a bad-coffee day.

[tedmich]

As Steve notes, motor start caps are not the ticket.

Sorry. I'm have a bad-coffee day.

typo, I believe the caps I referenced are PP run caps,

By all means incentive-ise GE to re-procure the 1/2m tons of PCBs it released into the environment that will be asserting their vast array of biological effects for the next several hundred years...As a chemist I simply think we should assume new chemicals to be dangerous until proven otherwise and before they become so profitable and entrenched that the companies can do the harsh math of profits vs suffering. I believe the POPs Treaty is designed to actually remove the toxins from the environment but someone powerful in the US doesn't want to pay to clean up the mess they made...is it you RG? have you been lobbying congress? no I didn't think so...

\This may make you laugh if you haven't already seen it...or even if you have... audiophiles hate scientists/engineers as much as fundamentalists do...perhaps more because they (unfortunately) need them...

Stereophile: Scientists vs Audiophiles 1999

[Steve Conner]

Ooh! This thread is straying well off topic.

I have a few stories related to the eco-criminal thing.

In my neighbourhood, people like to dump their old refrigerators on the kerbside. The council are supposed to collect them for recycling, but usually RG's "copper finders" get to them first. They rip the compressor out to sell for scrap, leaving the rest of the fridge. And letting out all of the lovely ozone-destroying CFCs. Sure, newer fridges use ozone-friendly refrigerants, but people don't throw out newer fridges.

I also know a guy who worked on the commissioning of a plasma incinerator for destroying Halon. Halon is a CFC used in fire extinguishing systems for high-value, high-risk plant like mainframe computers and indoor substations. It's extremely dangerous to the ozone layer, and recently banned just like PCBs. (Ironically, if they hadn't banned PCBs, substations might never have needed Halon systems.)

So, they thought they would have a market for getting rid of it safely. But when it came time to decommission these old fire systems, the Halon all mysteriously disappeared! Wonder where it went?

The incinerator sat idle until the facility went bust.

I personally worked on a system for detecting methane emissions from landfill sites. Methane is a greenhouse gas, and there are legal limits for such things, farting cows notwithstanding. On its first trial, it detected illegal levels of emission, and the landfill site owner's reaction was to boot us off his site.

The trouble with incentives is that somebody has to stump up the cash to fund them. Laws don't cost anything, but enforcing them does. And the Earth can't bill you for its services.

[tedmich]

Ooh! This thread is straying well off topic.

I have a few stories related to the eco-criminal thing.

In my neighbourhood, people like to dump their old refrigerators on the kerbside. The council are supposed to collect them for recycling, but usually RG's "copper finders" get to them first. They rip the compressor out to sell for scrap, leaving the rest of the fridge. And letting out all of the lovely ozone-destroying CFCs. Sure, newer fridges use ozone-friendly refrigerants, but people don't throw out newer fridges.

I also know a guy who worked on the commissioning of a plasma incinerator for destroying Halon. Halon is a CFC used in fire extinguishing systems for high-value, high-risk plant like mainframe computers and indoor substations. It's extremely dangerous to the ozone layer, and recently banned just like PCBs. (Ironically, if they hadn't banned PCBs, substations might never have needed Halon systems.)

So, they thought they would have a market for getting rid of it safely. But when it came time to decommission these old fire systems, the Halon all mysteriously disappeared! Wonder where it went?

The incinerator sat idle until the facility went bust.

I personally worked on a system for detecting methane emissions from landfill sites. Methane is a greenhouse gas, and there are legal limits for such things, farting cows notwithstanding. On its first trial, it detected illegal levels of emission, and the landfill site owner's reaction was to boot us off his site.

The trouble with incentives is that somebody has to stump up the cash to fund them. Laws don't cost anything, but enforcing them does. And the Earth can't bill you for its services.

Best phrase I have heard for understanding occurrences in the US (and to a slightly lesser degree our semi socialist neighbor to the north)

"If it doesn't make sense, it must make money"

a corollary for religions

"If it doesn't make sense, it must make babies"


Trivia: Mr. Thomas Midgley Jr invented both freon and tetraethyl lead for gasoline! (and accidentally hung himself with a rope pulley contraption he designed to counteract his polio.)

[guitician]

Hey the metalized poly caps are "Self Healing"! We may be on to something.....
These motor run caps may work.......The AC to DC voltage ratings would need to be figured too.....
http://www.cde.com/catalogs/SF.pdf

It looks like they still use paper too....
http://www.cde.com/catalogs/T.pdf

[Prairie Dawg]

the association of PIO caps with massive PCB pollution is enough for me to completely avoid them. No audio qualities counterbalance their environmental impact, as they are commonly disposed of improperly. Of course the Mfg were the worst offenders, like GE releasing >500 tons into the Hudson River from their two capacitor manufacturing plants at Hudson Falls and Fort Edward, or Westinghouse in Indiana, or who knows what Soviet era factories today...

I've heard grizzled old techs mutter about how they haven't observed any increased cancer rates but that bad karma has to go somewhere...

Some of that stuff got loose in the environment in Michigan during the seventies. It was PBBs (polybrominated biphenyl) but same nasty stuff. Whole lotta bad mojo. The company that made the stuff used the suffix -master for their bagged products. They also made a feed supplement for cattle called Feedmaster-magnesium oxide I think. Well, they also made PCBs in the same size bags called Firemaster. Several bags of PCBs ended up in a feed mill in Climax, Michigan and before it was over the state had had to bury 20 or 30,000 head of cattle up by Kalkaska.

That happened back in the seventies....

The Michigan PBB disaster@Everything2.com

[R.G.]

As a chemist I simply think we should assume new chemicals to be dangerous until proven otherwise and before they become so profitable and entrenched that the companies can do the harsh math of profits vs suffering.

This is another of those things which is susceptible to engineering solutions to social problems. Require the CFO and CEO of any company selling any new chemical product to eat a pound of it unless it's declared to be non-toxic.

We don't use self-interest properly.

is it you RG? have you been lobbying congress? no I didn't think so...

Sadly, no. I can only wish I had enough money to lobby congress.

\This may make you laugh if you haven't already seen it...or even if you have... audiophiles hate scientists/engineers as much as fundamentalists do...perhaps more because they (unfortunately) need them...

Hadn't seen it. Thanks! Now my sides hurt from laughing...

In my neighbourhood, people like to dump their old refrigerators on the kerbside. The council are supposed to collect them for recycling, but usually RG's "copper finders" get to them first. They rip the compressor out to sell for scrap, leaving the rest of the fridge. And letting out all of the lovely ozone-destroying CFCs. Sure, newer fridges use ozone-friendly refrigerants, but people don't throw out newer fridges.

Easy - pay money for the freon. If the "copper finders" make more money as "freon finders", they'll be careful. Of course, our government's approach is to criminalize selling copper. As a result, you now have to >be fingerprinted and photographed< to sell scrap copper and aluminum. But then having dossiers on everyone is a Good Thing if you're an apparatchnik. Didn't the old Soviet Union go broke doing this? Why, oh why must our political heros insist on doing it all over?

The trouble with incentives is that somebody has to stump up the cash to fund them. Laws don't cost anything, but enforcing them does. And the Earth can't bill you for its services.

I used to think that coming up with cash to fund things was an issue with governments. I now know that the USA at least can simply piss away a trillion dollars on "stimulus" which doesn't. A remarkably few *billion* of those dollars would buy a terriffic irregular army of eco-scavengers trying with all their ingenuity to track down and haul in any contaminants they could find.

It would be successful; as such, it will never happen. The financial incentives for hauling in a dead passenger pigeon were much smaller and look what happened to them.