Shelf life of caps in stored/barely used gear?

[tINY]

In LA you should be fine. The biggest issue will be condensation from humidity and cold temperature...



-tINY

[Wavebourn]

1. Probability of failures have an exponential law, so older gear is more reliable (MTBF does not mean that it will fail over equal periods of time)
2. Extreme temperatures (especially below 0 and above 100) greatly increase probability of failures.
3. I heard of training of electrolytics by variacs, but I have no valid proof why it is needed.
However, it is a good practice to check your gear in advance before it is needed, especially when it has switches and sockets.

[cornutt]

Originally Posted by Wavebourn

3. I heard of training of electrolytics by variacs, but I have no valid proof why it is needed.
However, it is a good practice to check your gear in advance before it is needed, especially when it has switches and sockets.

There's a lot of theory about re-forming the electrolyte in the caps. As you say, with modern caps, it's probably overkill. However, what is important is to limit the inrush current to the totally discharged caps -- they are going to look like a short circuit for the first fraction of a second, and besides stressing other power supply components, it isn't good for the caps themselves. The inrush can create an arc through the cap or boil the electrolyte. That's the main motivation for the variac.

If you don't have a variac, a decent substitute technique is to gather up every extension cord you can find (at least 150' worth), and use that to power up the gear for the first time. The series resistance of all of the extension cords will do a reasonably good job of limiting the inrush.

[ulysses]

Another advantage to using a variac when first bringing up power on gear that's been in storage is so that you can measure the rails as you ramp up the mains voltage, and catch any problems before they have a chance to smoke anything expensive. If your -18V rail is shorted by a bad cap, for example, you'll be glad to notice while you're only feeding 25% of nominal mains voltage.

I like the extension cords idea for a quick and dirty solution. The power limiter I've always liked is where you wire a 100W light bulb in series with an outlet. If the bulb lights up fully, it means your gear is broken. If not, then you just eased power into your gear without a big inrush current.

[idylldon]

Originally Posted by ulysses

The power limiter I've always liked is where you wire a 100W light bulb in series with an outlet. If the bulb lights up fully, it means your gear is broken. If not, then you just eased power into your gear without a big inrush current.

Yep. I have one of these wired up on my bench for just this purpose. Works like a charm.

Cheers,
--
Don

[Wavebourn]

Now, the question is: how did you know that bringing up a voltage slowly you restored the cap? What if it was good without such "restoration"?
I understand the reason why to use a current limiter (I myself switch through a table lamp unknown devices), but I don't understand how "reforming the caps" work physically/chemically.

I think it is a myth, kind of urban legend that helps to inflate egos of some guruing repair technicians.

[cornutt]

Originally Posted by Wavebourn

Now, the question is: how did you know that bringing up a voltage slowly you restored the cap? What if it was good without such "restoration"?
I understand the reason why to use a current limiter (I myself switch through a table lamp unknown devices), but I don't understand how "reforming the caps" work physically/chemically.

I don't either, to be honest. I know the antique radio guys have all kinds of elaborate procedures they go through. I'm not sure how much of it is necessary and how much is religious ritual. Posslbly it makes a difference with those old askarel-filled caps.

[ulysses]

I know the process, I just don't know if it's true. The process (supposedly) is electrolysis. If you were to reverse-bias a polarized electrolytic capacitor, electrolysis would cause the metal deposited on the the dielectric to travel through the electrolyte and deposit itself on the facing dielectric. Having metal on both facing dielectric surfaces and swimming around the electrolyte creates paths for arcing at lower voltages than normally required to destroy a cap. When arcing does occur, it vaporizes the material in the immediate vicinity of the arc so that an open circuit is created rather than a short circuit (in good modern Aluminum electrolytics). The cap is destroyed.

The conventional wisdom is that if you leave a cap sitting for a long time without a polarizing voltage, the metal will sort of wander around the electrolyte instead of remaining solidly electrolyzed to the proper side of the dielectric. Again, this is supposed to create lower-voltage paths for arcing. By ramping up the voltage slowly, it's theorized that the metal can electrolyze back to its proper dielectric surface and eliminate those lower-voltage paths before the capacitor sees enough voltage to make use of them.

Wavebourn, you could perform a study to find out whether or not there's any merit to this theory - or at least to the conventional process of dealing with it. Take 200 fresh electrolytic capacitors. Or you could use up some stale old stock, so long as they were all stored identically. You could use a variety of capacitance values, brands, and ratings, but let's stick with one voltage rating (100V) and one temperature rating (85C). Set up 100 of them to sit with a proper bias voltage across them, maybe 90V. Set up the other 100 to sit with a small reverse bias on them - maybe -0.3V or so. Not enough to destroy the cap outright. Let them all sit for a period of time you deem sufficient. If you keep them at an elevated temperature, you won't have to store them as long. Maybe 6 months at 75 degrees C. Then power them down and store them without bias for maybe a month.
Next, take 50 of each batch of capacitors and apply a sudden bias voltage of 90V. Take the other 50 of each batch and ramp up the voltage slowly from 0 to 90V over the course of an hour. You now have 4 groups to compare failure rates - with and without storage bias, with and without soft-start for their return to service. Unfortunately this test will take a very long time, and it might require repeating to find a set of conditions that produces enough failures to be meaningful.

[Wavebourn]

Thanks Ulysses; I can perform such a study if you are going to finance it. I even can publish results in some magazine, say in AudioXpress, or in Elektor that is new for USA readers.

[Fleaman]

Originally Posted by tINY

In LA you should be fine. The biggest issue will be condensation from humidity and cold temperature...
-tINY

I appreciate the interest in this thread, yet it seems only Tiny has directly answered my question(s).

Ultimately it's been on topic (caps/shelf life, etc.), yet I'm still wondering if I need to power up my gear once in a while or leave it alone?

Any other thoughts on this particular issue?

[tINY]

Yeah, you should get it out and make music occasionally...




-tINY

[Fleaman]

Maybe another year or 2 before I get into another studio.

Some gear I can and do use, but most of it I can't....especially the console. But I can power them up if need be, for the health of the caps....just don't know if that will cause more harm than good.

[cornutt]

I'm thinking it might be good if you can power them up every 60 days or so, but if it's going to be a year between power-ups, it might be better to leave them be until you're ready to use them. Just a SWAG on my part, though.

[Fleaman]

Just read a thread here about a posters SSL AWS900 going down (pwr supply issues) and the SSL tech told him to plug his 900 direcly into the wall, not through the AC conditioners/regulators that he had it hooked up to. Mentioned something about the initial pwr up being a big draw (spike) and that the regulators might not have the capacity to handle it, causing a dip in pwr and possibly popping his pwr supply cards in the AWS 900.

With the good suggestions here about using a variac or super long extension cords or lightbulbs wired in series for gear not powered up in a while, can there really be possibility of damage done by slowing the power up spike?

[ulysses]

Originally Posted by Fleaman

...tech told him to plug his 900 direcly into the wall, not through the AC conditioners/regulators that he had it hooked up to. Mentioned something about the initial pwr up being a big draw (spike) and that the regulators might not have the capacity to handle it, causing a dip in pwr and possibly popping his pwr supply cards in the AWS 900...can there really be possibility of damage done by slowing the power up spike?

No, that's ridiculous. If the power conditioner wasn't up to the challenge, the risk would be damage to the conditioner, not the gear. I think if I put my mind to it I could come up with a circuit that could be damaged by being underpowered, but it would be a challenge.

[Fleaman]

Yeah, I thought it was strange...but what do I know

Here is a partial quote from that thread: Ssl aws 900 died!!! - help tech's!!!!

Originally Posted by Ken Lewis

As far as power conditioners go, i got a surprising answer from the tech. I have a Monster Power 5100 on it, which is nearly top of the Monster line and should handle it just fine, BUT, the tech said he strongly recommends not plugging it into a power conditioner, and instead plugging it straight into the wall. I know, i found this odd too, but upon further questioning, he said that when the console first powers on it draws alot of juice all at once and sometimes the power conditioners dont handle that so well which can blow the power card.

I also asked him if he thought there was any sonic difference AT ALL between plugging it right into the wall or conditioning the power and he said "None". OK then. The wall it is.

I am plugging it straight into a 15 amp line (sorry not 20 but i think 15 will be fine for it), with nothing else on that circuit. Oh, he also said avoid APC battery backup scenario's too, and honestly, until very recently, i think my Monster conditioner that it was plugged into was going into an APC as well, so, probably a double whammy every time it got kicked off and back on. I've learned my lesson. Kinda like the first time you have to drop $1500 to recover a hard drive. After that your backup scheme gets ALOT tighter.

So, lessons learned. no power conditioner, plug it straight into the wall and dont share that line. check. No APC. check. no unplugging without turning it off even though the offswitch is a bitch to reach. check.

The tech did say that these things rarely ever break. I hope thats my experience from here on out. I will say this, you have to practically take the whole damn console apart to get to the power cards. a REAL pain. But hopefully i wont have to do that again for a very long time. -Ken

Note that the 'power card' he's talking about blowing is the AWS900 power card (in the console), not the power cards (if any) in the outside AC conditioners. And the advice he got was from an official SSL tech.

Maybe when a power conditioner or regulator is over worked/over drawn, it distorts like a power amp? And that distortion is what can damage the console power supply??

[Wavebourn]

I can give you more technical information, this time regarding power supplies, but I'm afraid you'll again treat it like a white noise.

[Fleaman]

Originally Posted by Wavebourn

I can give you more technical information, this time regarding power supplies, but I'm afraid you'll again treat it like a white noise.

Not sure what you mean by that

I at first asked a rather general and simple question (original post). Obviously there is no simple answer to it, hence the suggestions and theories provided.

I posted the SSL AWS900 scenario specifically because that SSL tech seems to advise contrary regarding the inrush of current. My only thought would be that it's not actually the inrush of current that damaged his power supply, but that the AC conditioners distorted in some why ('cos they couldn't handle the inrush), and maybe that caused the damage to the AWS900.

Or the SSL tech was on drugs....or the SSL owner just misinterpreted what the SSL tech said.

Remember, I'm not a 'tech'.

[nosebleedaudio]

I prefer power amps and large consoles to plug straight into a GOOD 20A plug, mainly because most low level conditioners have cheap AC outlets, and your going thru MORE wire/connectors...