How long are Sprague Atom filter caps good for time wise?

[catnine]

Time flies and I'm not certain how long ago i built this amp I have . I know the last time I worked on it to do a mod was Nov 10th 2008 . I think the last time I actually played through it was around Aug 2009. I know I built it sometime in 2006 yet I am not certain of the date so the filter caps are at least 6 and possibly 7 years old.. It does not have a lot of hours on it and I have had 30 year old fenders that I got that still were quiet and played well with all original filter caps that were the old yellow cardboard or paper wrapped caps and they showed no sign of leaking. This was when I got a 73 SF champ in the end of Jan 2005 and before that a 71 music master bass amp beginning of jan 2005 . My SF champ clone that i built in the beginning of dec 2007 sat as long as this build did and has F&T filter caps and I turned it on and it was fine.

I used to not knowing just get an old fender amp and turn it on , now that I know I am a bit leary just to turn it on or perhaps I should pull the chassis and have a look at the caps before I do . Any ideas?

See I get this way reading and posting all this stuff talking about adding fuses and safety and such.

[Enzo]

Well, I for one do not consider a 7 year old amp to be "old."

[Shawnobi]

I read somewhere that the rule of thumb for electrolytics was 15 years. Though I prefer the rule of 'if it ain't broke don't fix it'. If it has the old paper caps I would definetly replace though.

[Dave Curtis, dB AudioTech]

Letting them sit for a long time isn't good. Power 'em up (at least) every six months; that keeps the caps "formed".

[Chuck H]

Even the cap MFG's use to have a rotation plan that kept old caps off the shelves. Some even had return policies for caps over a certain age. Those days are long gone. As are stores where these things can sit on shelves. The point is, caps age whether in use or not. Actually much worse when not used. I wouldn't use a "new" cap over a year old without re forming it. Re forming for me simply means that I fire the amp up with a light bulb current limiter and let it burn in for 12 to 24 hours. I just toss anything that sits for more than two years. It's just less hassle to get new ones rather than go through a longer, more complex re forming process. Some guys say to stick them into a cardboard box and cut out a hole for a blow drier. Then warm the caps and alternately apply voltage via a Variac. people report restoring very old caps this way. I'll never do it. I know me. I'd sooner take a shortcut and blow something up.

Sprague ATOMs are too expensive for what they are. I've switched my construction method to accomodate radial caps just because of trouble I've had with ATOMs. No problem so far with Nichicon PW's. The Nichicons actually have specs you can find, unlike ATOM's. Just to recap (pun intended) I've had trouble with ATOM's. And they have no specs redily available to the consumer via any distributor. I once read here, from a well respected and very experienced member, that when a MFG decides to omit a certain spec from usual it means that the part probably rates poorly in that area. I've found this to be true over the years. And I can't get ANY specs on the Sprague ATOM caps!?! Hmmmm. And they're one of the more expensive caps sold for guitar amps too! I've been paying about 30% for very high spec Nichicons. They're smaller, spec better and I no longer have new amps with bad filter cap symptoms.

I say just plug in and see how it goes. If the caps are bad, replace them. Hopefully with something other than Sprague ATOMs.

Sorry for ranting.

[Jazz P Bass]

The useful life of an E cap depends on a few things.
Like temperature & the type, model #, of the cap.
A typical rating is in hours of use.
Most mfg's datasheets have the full specs.
http://nichicon-us.com/english/produ...f/aluminum.pdf
Here is a good read.http://www.cde.com/tech/reliability.pdf

[R.G.]

ESR meter.

[Gtr_tech]

ESR meters only tell a little of the whole story. With HV filter caps, I rarely see them go high ESR. I do see them go leaky....all the time. Thats what you need to watch for....

Ultraminiature radials in flatscreen TVs and other consumer junk often have ESR issues and severe leakage before they pop the top.

[nickb]

To quote from one the refs that Jazz P gave above:

"Generally, if the capacitor has been stored within 2
years in the storage temperature range of 5~35C, the
capacitor can be used without voltage (i.e reforming) treatment."

[1ampman]

I don't think the Atom caps are made in the States. I believe Taiwan and the prices are crazy. As stated NO Specs? A lot of mystery...

[stokes]

The Atoms are still made in the states,all the other Spragues are made overseas.I havent had any issues with the Atoms,yet.I have heard more people these days talk of issues,but I aint seen it yet.In the last 2-3 years I've done a lot of re-caps 30 or so a year.I have taken to using F&T's of late,because of the price.I've always used Sprague and F&T's,at least since the late '80's when I swore off the asian stuff,saw more failures with them.I still do pre-form caps before installation,its the way I learned and you never can be sure how long they sat unused.It may not be totally needed,but it puts my mind at ease and you know,"teach an old dog..." I had a supplier,the last guy in "radio row",went out of business in the '90's and he said the suppliers gave a ten year shelf life,like Chuck said,they would actually come in and rotate the stock.Not anymore,but I would think the ten yr shelf life would still stand.In my own amps I change them at or around ten years,and I have a lot of amps.I always see an improvement,tightens things up.

[catnine]

I posted asking how long Sprague Atom caps last.
I powered up the amp with the bias rite installed just to see if everything was ok.
I had nothing plugged in the inputs yet when I turned to vol pot up just a bit at times I would hears a crackle throug the speaker so i decided to pull the chassis and take a look thinking perhaps the pot was dirty. I began by checking the resister values just to see where they were and the first one I checked was the 1.5K from the V1 to ground and the resister lead at the ground side popped off so it must have been intermitent. So with nothing plugged in and the amp at idle with no ground on the V1 cathode but just the bypass cap what would that do as far as the 12AY7 is concerned? I repaired the problem the caps seemed ok . Trouble is on this weber 5E3 eyelet board the resisters for the cathode bias with bypass caps on V1 and V2 do not have leads long enough to bend over for a physical joint so at the time I just soldered them to the leads of the bypass caps and right on the edge of the eyelet , apparently they over time even with a good solder joint must have expaned and contracted enough to pop loose. This time I bent a loop in the resister leads and crimped the loop around the bypass cap leads and then soldered them witha bit more slack.