Lifespan of a quality solid state amplifier?

English is an evolving language.

'Half life' works really well in this case since you have the statistical issues of a single cap and also that of several.

In the case of a single cap its half life is 20 years on average. IOW, you will find that it may well have dropped to half its capacity, with its ESR likely more than doubled. I have never seen caps over 40 years old that are safe to operate; but by that time they should be replaced, without question.

In the case of a bank of filter caps it will be found that in 20 years time half of them have reached the end of their useful service life, by leakage, by shorting, or simply so ineffective that the equipment using it no longer meets spec.

It seems that 'half life' works very well for this. However if sensibilities are offended (we're not in Alice's Wonderland, apparently) then MTBF is fine.

Herman, A few years ago I heard about a Chinese firm doing some corporate espionage. Apparently Panasonic had developed a more effective dielectric for their electrolytic caps. Fearing the discovery of their formula by competitors, they kept it in 2 halves in different locations. How I heard it was that the Chinese company had managed to get one of those halves and used it in their caps, which got used in a lot of computer boards that began failing about 6-8 years ago on this account. Is this anything like what your firm was experiencing?

.

Ralph,

Again, I'm dumbfounded you continue to defend what is clearly wrong.

I've been dealing with electronics for over 30 years, taught it for 10, and have looked at this topic quite a bit since it often comes up on this and other forums. I've never seen it mentioned that 1/2 fail in 20 years or any other statistic that puts a lifetime like that on them. Any data always factors in temperature and voltage. I really respect most of what you say here but you clearly have no real data to back up any of these 20 year claims.

Yes, English evolves but that doesn't mean it is acceptable to use it in any way you wish. Half life has a very clear, concise, scientific definition and your use of it is well outside that definition. Ir would be nice if someone on these forums would just once admit they are wrong.

MTBF to describe cap failure is also incorrect as stated above. It refers to complex, repairable devices, not components. How can you possibly have a "mean time BETWEEN failures" for a device that is thrown away when it fails? There is never a second failure so there can never be a between. From this article

MTBF is properly used only for components that can be repaired and returned to service.

Yes, I suspect the caps we are seeing fail are part of what you talked about. I posted a link to it in my response above.

.

Good question. I don't think there is really much required in the way of care and feeding. I am on more than 20 years on my PS Audio 250 Deltas, and they still sound fantastic.

That said, there are problems that crop up with amplifiers, tubed as well as solid-state, lord knows why.

Not sure that there is really a defined lifespan, but for the prices we pay for some of this stuff, it should be forEVER, right?

True story: I had a 1960 Fender Deluxe guitar amp (brown tolex vibrato version...no reverb) that I thought needed attention (I'd owned and used it as a studio amp for 35 years or so) before selling it (mistake). It had old leakey caps...a reliable tech swapped 'em out for nice new ones resulting in my amp sounding exactly the same.

A couple of things. 1) most decent amplifiers have soft/slow start circuitry which prevents the on/off cycling problems that people mention here. Therefore for a decent high end amp, the cycling on/off damage they are talking about really isn't an issue anymore. 2). Electrolytic capacitors would be a problem and must be checked. They are like any other component in cars, etc. they give you advanced warning that they may probably fail. yes, yes, there are instances where something just simply goes out, but in most parts you can see leakage before they fail. So, take a good look inside or have a qualified technician inspect the unit to see if any problems may exist. If nothing is apparant, then leave it alone until some problem or possibility of problem presents itself. 3) apart from capacitors, the thermal damage due to the loss of heat sink compound that the transistors are using when connecting to heat sinks may be the major issue. Transistors fail for a number of reasons. a) people that short the outputs when playing with speaker cables are the number one reason. b) when the heat sink compound dries out, it presents a problem for loss of thermal conductivitity and also allows for the possibility of the transistor to come in contact with the heat sink, because not only is the heat sink compound gone, but the thermal insulator between the transistor and the heat sink may be damaged. Therefore, what I typically do with older amplifiers is to check the capacitors for leakage and replace if necessary (only if necessary) these suckers are expensive, and replace all pre-driver and output driver power transistors with the newest, latest and greatest more linear transistors and readjust the bias, which makes the amp much better sounding. This also allows me to replace the thermal insulators and the heat sink compound, thereby eliminating any possibility of the amp having issues. my "modified" amps are much better sounding then the original and also are much longer lasting because I have inspected and replaced capacitors where necessary and also I have replaced all pre-driver and output power transistors and their associated thermal insulators and heat sink thermal compound.

One last thing. I typically will add a slow start/turn on relay circuit to any amp that does not have it originally and I sometimes will modify the power supply to separate power supplies with regulators.

After all that, I guess what I am saying is for really old amps, definitely change the heat sink compound and thermal insulators at a minimum and if you can change all output transistors also and check and replace if necessary the electrolytic capacitors.

enjoy