A simple answer is are they old when you measure them, or when you listen to them? Odds are you can measure changes before the ones that you can hear. I have a 32 year old APT 1 amplifier that sound good but the caps would invaribly test poorly by now, though.
And to that end, heat and years do add up. A hot class A amp will more than likely fall offs it performance curve before a cool running class D amplifier.
I agree with the 20 year "servicable" life. Anything after that is gravy with electrolytic caps. But MANY a component goes way past that. Capacitors are like valve tubes, same type tubes can go in a year, some decades. Same tube, different life. On solid state change years to decades and decades to 20 years. |
Years ago I had a PS Audio 200C amp and it wasnt sounding right. Called their tech and he told me that the life of the caps was about 15 to 20 years, depending on use. |
I like to rotate mine every six to twelve months. You know, so they get even wear. It sucks when you open up a case only to find one cap has all it's tread worn off and another looks brand new.
Hmmmm.... I'm thinking if two different things.
But seriously, this is a subject near and dear to my heart. Not only am I a lover of older SS amps (Citation 7.1/5.1, Acurus A250, Haflers, etc) but I also love to fiddle with older computers. I have a collection of motherboards from that wonderful period of the mid to late 90s when there was a batch of caps that had a stunningly high failure rate. On pretty much every one of those babies you can see the cap bubble. Yep, makes me want to get the ole soldering gun out right now.
Anyway, I've been trying to decide just when some of my amps need to be serviced. It is an expensive proposition, especially when you include shipping both ways. I'm hoping the Citations can run, say, another 30-50 years! (yea, I'm hoping that -I- can run another 30-50 years). ;) |
Rodman:
Yes, that is why tantalums are called "solid", although some military versions actually have a liquid electrolyte in them (VERY EXPENSIVE). The solid versions use MnO2 electrolytes that are produced by evaporating the salt solutions during manufacture.
They are not designed for power supply main filtering, only bypassing and for timing circuitry. They have very low leakage currents, about 1/10 of the leakage through Al electrolytics. They range from about 0.1 to 200-300 mFd. Outside this range they are not applicable. The larger capacitance versions can be very expensive.
One audio application I have used them for is the timing circuits in my Parasound JC-1. Replaced the Al electrolytics that Parasound used stock with tantalums and now my turn on time delays (there are three of them, sequential) are rock solid.
I would not recommend them for audio coupling due to their non-linear dissapation factors and dielectric performance. But they last forever. |
Although Tantalum caps are considered, "electrolytic"; there is no liquid electrolyte(totally different construction) to dry out, or expand and blow out the vent. Two major reasons for electrolytic failure. Solid polymer(ie: PEDOT) electrolytics are another excellent option, if applicable. Try finding either, in a value usable for a power amp PS filter cap though. I've installed Sanyo OS-CONs in my TACT preamp's PS, with excellent results. |
I recently put a Technics DD turntable from the late 80's back into service. I replaced EVERY electrolytic AL cap. Many were starting to show corrosion at one electrode.
Please remember you cannot judge the quality of 20 yr + old AL caps by specs of today's products. Back 20-30 years ago they were not as good as today's premium brands (not the cheapo stuff).
I have Tektronix O-scopes and electronic equipment from the 70's which used a lot of solid tantalum electrolytics. I have yet to see one of these fail. They are vastly superior to Al electrolytics from a lifetime perspective. |
I have a CJ PV-10A circa 1992. The Solens film caps in it while not the greatest caps never showed any noticeable agingissues. However the white "CJ" film caps definitely aged, deadening highs and transients; swapping with new caps gave immediate improvement. So cap type must have some bearing on life span. |
Bottom line is don't buy old gear unless you are prepared to replace all coupling caps, wire, lytics, tube sockets and tubes. This is quite common. Jallen |
The main reason to replace them is doing so may well result in an incidental upgrade/or deliberate one. Typically included in a complete overhaul. Well worth the average cost of around $400.00 for an amp. |
I guess I've replaced WAY too many electrolytics, in power amps, Leslies, Tubed Organs and speaker systems, pro and home(for myself as well as customers), to buy into some the above statements. |
>Tntate (Threads | Answers | This Thread)
>Cap life span?
On a tight budget. Looking at older amps and need to know if capacitors have a set lifespan. How would I know if they need replacing?
Get some big power resistors which can be wired in parallel to produce an 8 Ohm load with sufficient wattage and validate that your amplifiers aren't clipping at their rated output power.
Or buy an inexpensive ESR meter and validate
http://www.amazon.com/Anatek-Corporation-blueesrassy-Blue-Fully-assembled/dp/B005NI4WE4
In most cases they won't have been run hot enough for long enough to cause damage. |
>08-06-12: Reb1208
>When talk of replacing electrolytic caps comes up on this and other forums. Most people are concerned with the larger can style caps found in amps and preamps.
Those are generally (output capacitors on an OTL tube amp would be an exception) the only ones which see significant ripple currents which make them hot inside and therefore likely to fail.
>Overlooked are the dozens of small value electrolytic caps such as those found in cd players, remote controls, secondary power supplies etc etc.
For electronics only powered up where you're listening to them with reasonable ventilation I'd expect those to outlive their first owner.
>Never had a Electrolytic cap go bad on me.
My Lexicon home theater preamp became inoperable due to a failed electrolytic capacitor in the switching power supply which AFAIK was always powered up.
I've replaced electrolytics in my pinball machines where low power supply voltages resulted from the excessive ESR that developed - they really don't like the heat from all the miniature light bulbs in the back boxes. |
08-06-12: Rodman99999
>If you look at the datasheets of aluminum electrolytic caps; you'll find that their expected life spans are noted in hours, at a certain temperature.
Right. That's usually 85 degrees C but can be 105 degrees C which is hotter than boiling water.
Life doubles with each 10 degrees C lower. At a pleasant 20 degree C room temperature a "1000 hour" capacitor is good for 90,000 hours or 10 years of continuous service. 2000 hours is more typical which nets 20 years.
People who turn their equipment off when not listening and will find their electrolytic capacitors much longer lived. Averaging 8 hours a day they might last longer than you do. |
When talk of replacing electrolytic caps comes up on this and other forums. Most people are concerned with the larger can style caps found in amps and preamps. Overlooked are the dozens of small value electrolytic caps such as those found in cd players, remote controls, secondary power supplies etc etc. Looking at a spare cd transport I have in storage (that is 20 yrs old) I see about 30 small value electrolytic can style caps soldered to the circuit board. Do I worry about these caps being dried up? No, and I dont worry about the large caps in my 20yr old amp, 30+yr old receiver and many other pieces of equipment either. Never had a Electrolytic cap go bad on me. However, I never let my equipment sit dormant for any prolonged lenght of time. Including hooking up the spare transport and running it occasionally. Which I think is probably a key factor in prolonging the life of electrolytic caps and avoiding failure. |
If leaking then replace. Sometimes a new one is bad. If all is working and specs fine leave it alone. I like to change mine when I get a new tube amp, but this an ocd indulgence rather than a sonic necessity. Jallen |
If you look at the datasheets of aluminum electrolytic caps; you'll find that their expected life spans are noted in hours, at a certain temperature. Some datasheets even list an expected shelf-life. These sites each mention different ways caps age/lose their values: ( http://www.elna.co.jp/en/capacitor/alumi/trust/index.html ) ( http://chemi-con.com/u7002/life.php ) Some good info here: ( http://www.hans-egebo.dk/Tutorial/electrolytic_capacitors.htm ) If the amp is approaching the 20 year mark: A cap change is a good preventive maintenance measure, and you'll probably notice improved performance in the system's bass & overall dynamics. |
Tutate: this question has been thoroughly discussed. Search the Forum for threads. |
Many suggest changing electrolytic caps every 15-20 years. This is an estimate, like tube life, it can vary. My amp is 19 years old and I just sent it to the manufacturer and wanted them to change caps, they told me that the caps looked to be in great condition, and tested well also. They recommended not changing them, I took their recommendation. |
