[DVV]

Time for a nice new topic.

We all have some knowledge and some experiences in designing, constructing and tweaking - fine, so let's exchange them. Here's one.

Audiophiles talk much about exchanging filter capacitors. Fine, but how many know that a capacitor should ideally be "formed"?

In production, filter capacitors are simply run off a machine. Every n-th unit is picked up and tested for consistency, quality, capacity, etc, but the rest are simply packed and assumed to be of good working order. That's how we buy them and take them home.

Before you install a set of brand new, large capacity caps, where large is anything over 1,000uF, not to even mention 10,000uF and above, you should check if it works, and "form" it. "Forming" is simply letting the capacitor charge at a low current; low voltage is not necessary, assuming only the usual precautions you would have anyway regarding voltage (never ever let it run any nearer than 5V below its nominal CONSTANT working voltage rating, and even that's too high).

By charging it at low current, you:

1. Test it for proper operation;
2. Make sure the initial surge does not blow anything even if it shouldn't;
3. Properly polarize the capacitor before inserting it in the circuit, and
4. Allow for what little directivity there is on the foil inside.

Do that, and I'll take any and all bets such a capacitor will last no less than 30% longer than another of the same type which has not been "formed".

I do it using a lab power supply, which allows me to preset voltage and current. Yesterday, I did it with three types of capacitors, two for replacing those in my Harman/Kardon integrated amps, and one of my favorite kind, Siemens Sikorel, for a project I'm working on.

Most however don't have a lab power supply. Well, you can construct your own capacitor charger/former (sheesh, I patent this, a brand new type of product!) by using a reasonably sized  power transformer from 50 VA upwards, capable of delivering say 18V at 1 A (i.e. 20 VA). You could simply construct a standard rectifier, filtered by a say 4,700uF cap in parallel with 0.1uF, a 3-point regulator (e.g. 7815), after which comes another 10uF capacitor and a series placed resistor of 150 ohms, 2 W rating. This will limit the outgoing current and allow you to slowly charge the capacitor.

BEFORE YOU CONNECT IT, MAKE  V*E*R*Y*  SURE YOU GOT THE POLARITIES RIGHT, OR YOU MIGHT DISCOVER IT ACTS LIKE A SHRAPNEL HAND GRENADE IF CONNECTED THE WRONG WAY !!!

After say 2 minutes, disconnect the capacitor. Take it into your left hand and move it as far away as possible from your eyes. Take an old screwdriver or some such in your right hand and connect the capacitor plus and minus. You will get a hell of a spark and a loud bang - but you will discharge the cap. Fun, huh?

Repat this 3-4 times for every cap you need to charge. You end up with more of a cap that if you hadn't done that.

I compared those without and with such treatment. Now, I must say at once that my results are very general and hardly scientific, but I find properly formed caps to be able to soak up 10-15% more current than those which have not been formed, and I can attest to the fact that they last longer from my own experience.

I know this is a little exotic, but hey, I'm sick and tired of being told I should use a green felt pen around the rim of my CD, or that I should freeze it.

Cheers,
DVV

[MaxCast]

Well, after 30 something views I'll say WAF!  I just wish you'd come over to my house and tweek the $#!^ out of my gear.  Bring yours too so I can get a ref of what you like  

[DVV]

Well, after 30 something views I'll say WAF!  I just wish you'd come over to my house and tweek the $#!^ out of my gear.  Bring yours too so I can get a ref of what you like  

Max, this is NOT impossible (well, in absolute terms, nothing is, but I mean in real world terms). Not too sure about bringing my gear though, it tends to crowd airplanes, and besides, I don't want to have to fight it out with you upon leaving, I already did that upon buying it with my wife.

Cheers,
DVV

[Gizmo Student]

Subwoofer Tip
For 2 channel sytems ....

Place down firing sub's 2 feet off the ground on a
sturdy, heavy and flat topped stand / piece of furniture -
between the speakers.

Front firing sub's should be placed lower
but still off the ground between the speakers.

Give them large lower range frequency waves
room to "breathe".

Gizmo Student

[Haoleb]

and instead of just using a boring ole screwdriver to discharge the caps, find more entertaining things, like the neighbors cat, or maybe the leads to a lightbulb or the metal ring around the gas tank hole in your caror stick it in one of those static proof bags with puter chips, close and shake until you see sparks. lol
id think you would want to put alligator clips on the cap leads and then touch those, so you dont accidentaly weld a screwdriver to the cap leads  

[DVV]

and instead of just using a boring ole screwdriver to discharge the caps, find more entertaining things, like the neighbors cat, or maybe the leads to a lightbulb or the metal ring around the gas tank hole in your caror stick it in one of those static proof bags with puter chips, close and shake until you see sparks. lol
id think you would want to put alligator clips on the cap leads and then touch those, so you dont accidentaly weld a screwdriver to the cap leads  

Alligator clips are standard issue in any lab, however small or large. Obviously I'll use alligator clips, I'm not going to solder those caps just to form them.

As for the neighbor's cat while discharging, you would very likely kill it with larger caps, and who knows, that neighbor might be playing with a .357 magnum as we speak.

Cheers,
DVV

[Audio Al]

Haoleb,
Your comment about shocking cats was not very P.C. (pussy correct).   Remember Teddy the audiophile feline is watching!

[Marbles]

What's with the Jeffrey Dahmer notation?

Did he eat pussy too?

[Audio Al]

Dahmer tortured animals when he was a child and look what he developed into......I think he owned a Bose stereo.
I doubt he ever ate pussy, he preferred boys.

[JohnR]

DVV, why don't you discharge the caps through a resistor?

[Lost81]

I second JohnR's suggestion.

Won't the massive amount of current developed as a result of shorting the electrolytic capacitor severely shorten its life?

Some of the electronic hobby sites I visit, often bemoan the fact that most electrolytic capacitors do not last long when utilized in this manner, unless they were specifically designed for such duties.

Won't a large 5W flame-resistant resistor be better for discharging?

Just a thought.

Cheers,
benny
---
Look, one says to oneself, look how cold the world is growing. Some more years will pass, and after them will come gloomy solitude; then will come old age trembling on its crutch, and after it misery and desolation. Your fantastic world will grow pale, your dreams will fade and die and will fall like yellow leaves from the trees... (White Nights, Feodor Dostoevsky)

[DVV]

DVV, why don't you discharge the caps through a resistor?

1. Takes too long;
2. Requires high power resistors if you want speed;
3. Not dramatic enough.

Cheers,
DVV

[DVV]

I second JohnR's suggestion.

Won't the massive amount of current developed as a result of shorting the electrolytic capacitor severely shorten its life?

Some of the electronic hobby sites I visit, often bemoan the fact that most electrolytic capacitors do not last long when utilized in this manner, unless they were specifically designed for such duties.

Won't a large 5W flame-resistant resistor be better for discharging?

Just a thought.

Cheers,
benny
---
Look, one says to oneself, look how cold the world is growing. Some more years will pass, and after them will come gloomy solitude; then will come old age trembling on its crutch, and after it misery and desolation. Your fantastic world will grow pale, your dreams will fade and die and will fall like yellow leaves from the trees... (White Nights, Feodor Dostoevsky)

Benny, I do not use caps that way all the time, just the first time. I want it to discharge quickly, and using resistors will take much longer and you'll never be sure some charge was not left over. But it's mostly the speed of discharge, which I want to be there. In case anything is amiss in the caps, it will show up then most likely.

As for charging, that should be done slowly, let it really soak up all the current it can.

Works for me.

Cheers,
DVV

[ABEX]

Wonder if you could market a unit to do these things for you.Just hook up leads and run through a list.

[DVV]

Wonder if you could market a unit to do these things for you.Just hook up leads and run through a list.

Not worth it, I think. For a start, not many people do this, partly because not many know about it, and partly because this really addresses the hard core tweaker group.

Then, putting together a power transformer, bridge rectifier, filter caps, three point regulator and a few odds and ends, is cheap anough, but shipping it around the world makes it expensive, much more so that if you walked into your local store and bought it over the counter. These are really cheap parts, and it makes little difference whether your transformer is a top class toroid, or an ancient unit out of some long gone TV set, so long as it delivers the juice.

You see what I mean? Doesn't make sense.

Cheers,
DVV

[ABEX]

Yes, I see what you are saying.Just thought for convience that a burnin product might sell like cable burner's do and not many people know of the tweek which might be a selling line for manufactures.

[DVV]

Yes, I see what you are saying.Just thought for convience that a burnin product might sell like cable burner's do and not many people know of the tweek which might be a selling line for manufactures.

Ah, so you want to get into the business?

OK, here's another one for you - CD Burn-In add-ons.

All you need are two reasonable quality RCA Cinch jacks and two 4K7/1W resistors. Solder a resistor across the RCA plug on the inside, repeat procedure with the other. Plug up the RCA jacks, pack in plastic bag, and sell for $20 as an ideal tool for burining in CD players.

Rationale - 4K7, or 4,700 ohms, is way below what the CD player will ever be asked to drive in real life. BUT, it is also way above the minimum rating of most op amp circuits, or discrete equivalent. So, you will be pushing them to deliver more current than they ever really will, but still far less than is their threshold of danger. Result - express burn-in inside of 48 hours, if you put in a CD, select "Repat all" function and let the poor thing work for 48 hours.

The magic - no other way known to me will produce a better sounding CD player than this, and certainly not in such a short time.

I just-a make-a you an offer you can't-a refuse. ("Godfather I" is on TV as I write this).

Cheers,
DVV

[karthikn]

Before you install a set of brand new, large capacity caps, where large is anything over 1,000uF, not to even mention 10,000uF and above, you should check if it works, and "form" it. "Forming" is simply letting the capacitor charge at a low current; low voltage is not necessary, assuming only the usual precautions you would have anyway regarding voltage (never ever let it run any nearer than 5V below its nominal CONSTANT working voltage rating, and even that's too high).

Link was explaining the chemistry of capacitor forming.  Scroll down half a page.Capacitor forming chemistry