What is the effect of age on audio components?

I have a 1978 year power amp. It seems to be ok, but do old components degrade gradually, or do they just fail all at once. In order words, how do I know I am still getting all that the spec sheet says is avalible. Talk about old components. Thank you.
Age effects vary with the type of component involved. For solid state power amps, the most common problem is that power supply capacitors can deteriorate with age. That can result in an increase in noise. Cap failure can also completely disable the amp.

Audio equipment with mechanical components can physically wear - lubrication dries out, rubber parts harden, mechanical pieces go out of spec from wear, and so on.

Tubes don't go bad just from age if they are not used, but they do have an in-use lifespan. I just had to replace the KT88 outputs in my 10 year old power amp as an example.

Lasers can fail with age on CD players, speaker surrounds can deteriorate and spider assemblies stretch to continue a partial list.

A few of these ageing issues can be spotted by a lay person, but many require specialized equipment and technical knowledge to check and repair. The only way to tell if an amp that seems to sound OK is still meeting its original specs is to put it on the test bench and measure.

If I had a 30 or 40 year old piece of equipment that I absolutely loved, I'd think it a pretty good idea to have it checked by a good tech. The danger is that sometimes when a part in audio electronics fail, it takes other items with it.
In addition to Mlsstl's excellent response, you may find the following thread to be of interest. The bottom line: it's very unpredictable.


-- Al
For an amp of 1978 that has seen regular use, the dominant factor will be how hot it runs. A high-bias amp will dry out the capacitors much quicker than one that runs cool. They will degrade slowly, but then can short out all of a sudden.

But there are many other factors that also contribute to longevity, like the quality of the caps, their ratings and type, how much voltage stress they see in operation, where they are located in the chassis, chassis cooling, if the amp wasn't used for long periods of time, the available space around the amp when it is used, if something was stacked on top of it, the typical ambient temperature in the room, the humidity, etc. This is why generalizations lead to unpredictability.