Is age bad for solid state amps?

The above comments are generally correct, as is the comment that an amp made in 1998 is not old.

I would add, however, that age with solid-state amps is more of an issue than it is with tube amps. The output transistors in solid-state amps can go out of production, and if such an amp loses an output device, it can't be fixed and the amp is toast. This won't happen to a tube amp that uses output tubes common in the tens of thousands of tubed guitar amps that are sold each year, e.g., EL-34's, 6L6, 6V6, 6550, etc., or that use a classic triode like the 300B, i.e., this won't happen with most tube amps.

In addition, when a solid-state amp breaks, it usually has to be sent to a tech or to the manufacturer to be repaired. When a tube amp malfunctions, it's more often than not a tube that is the source of the problem, and they are user-replaceable.

Finally, with a tube amp, the tubes are the circuit, and when the amp is retubed, it's basically a brand-new new amp.

While they tend to be reliable, output transistors can and do fail. The following is a useful summary of the issues (note: the British term for "tube" is "valve"):

"Transistors also have their fair share of problems, and there are some things that they are just not very good at. Some of the major failings include:

* Low Impedance - Bipolar transistors are inherently low impedance, and additional circuitry is needed to make them work satisfactorily in high impedance circuitry. Noise is also a problem when high impedance sources are used.
* Heat - Transistors dislike heat, and if it is not removed, they will destroy themselves. Most transistors can operate with junction temperatures up to about 125 degrees C, but at that temperature, can do no work at all. The life of a transistor is severely shortened by operating at high temperatures.
* Thermal Stability - Transistors are subject to some major changes in operation, depending on their temperature. This can make the design of high quality amplifiers difficult, because the transistor has a tendency towards "thermal runaway". This means that as the device gets hotter, it will draw more current, which makes it get hotter still. This continues until the maximum operating temperature is exceeded, and the transistor(s) fail.
* Second Breakdown - This is a version of thermal runaway, but at a molecular level. Parts of the internal structure become hotter than others, causing the hottest part to do the most work. This makes it hotter still until the transistor fails. Second breakdown is the most common cause of output transistor failure in power amps. It also happens very fast, and without warning - transistors can fail from second breakdown even when at ambient temperature.
* Short-term Overload - Largely due to second breakdown effects, transistors do not tolerate short term overloads, and in many cases even a momentary short circuit will cause instantaneous failure. Compared to valves, transistor circuits are much less capable with difficult loads, and usually must be over-engineered to sometimes extreme levels to prevent failures.
* Hard Overload - when a transistor amp goes into overload, it does so with startling clarity. The harmonics produced are such that tweeters can be destroyed very easily, and the sound is altogether unpleasant

Again, there are many advantages as well. Transistor amplifiers are very reliable, and can be counted on to give many years of life without requiring even a basic service (most of the time anyway)."

Source: http://sound.westhost.com/amp-basics2.htm