Amp not enough power

As you probably realize, the 4004MkII is rated at 200W and 400W into 8 and 4 ohms respectively. At the time it was introduced, FTC requirements for amplifier power ratings specified a "pre-conditioning" prior to the measurements, comprised of 1 hour of operation driving a 1kHz signal into an 8 ohm or 4 ohm resistive load, at 1/3 of rated power. I believe that about 10 years ago the pre-conditioning requirements were revised to something less stringent.

I would question the tech as to how he did the pre-conditioning. If it was for longer than 1 hour, or at more than 1/3 of rated power, that might account for the 4 ohm measurement being less than 400W.

Also, I would ask him what the temperature conditions of the room were at the time. In a hot, non-air conditioned environment it is also conceivable that the measurement would be reduced.

Regards,
-- Al

Does electronics degrade and changes the quality/sound of the amp?

Yes. Capacitors tend to be the most common culprits, aside from tubes in tubed equipment. Electrolytic capacitors in the power supply circuits could affect power capability, as well as sound quality. Smaller capacitors elsewhere in the circuitry, especially if they are directly in the signal path, could affect sound quality.

However, if the only indication of a problem is the max power measurements you were provided with, I would not take any action until the tech answers the questions that I and Eldartford stated.

If you and the tech do conclude that the electrolytic capacitors are probably causing a reduction in power capability, and you decide to have them replaced, it would probably make sense to have as many other capacitors as practicable replaced at the same time.

More generally, concerning the ability of older equipment to work well, the following threads will make for interesting reading. The upshot is that the performance of older equipment is very hit or miss, with little predictability, but in the better cases older equipment can continue to work well for MUCH longer than might be expected.

http://forum.audiogon.com/cgi-bin/fr.pl?htech&1267845685

http://forum.audiogon.com/cgi-bin/fr.pl?ymisc&1274033569

Regards,
-- Al