Levinson 20.5 monos - Time for a Refurb?

Common thinking, (old wives tale?) is that caps are good for about 20 years. The look-see price seems more than a bit steep. If your amps seem fine, perhaps the maintance is a bit premature. I'd suggest waiting a little while and then if you still want the amps, have them looked at. That is, unless of course they begin to dissapoint or flat out fail.

Common thinking, (old wives tale?) is that caps are good for about 20 years.

What does that mean? Do you think they don't last that long or that they last longer.

For all naysayers, if you do a little research you will find there is indisputable proof backed by numerous studies that electrolytic capacitors deteriorate over their lifetime losing both capacitance and suffering an increase in effective series resistance. It is also true that the rate of deterioration is directly proportional to how hot they get. There are also other components that can shift in value after operating in a hot environment for so many years.

The fact that this deterioration happens very slowly means that it is very difficult to discern how it affects the performance of the amps, but I guarantee they are not performing as they did 16 years ago. I have rebuilt many vintage guitar tube amps which mostly consists of replacing all the bypass and power supply electrolytic caps along with any carbon composition resistors that are out of spec. The resistors tend to increase in value. The owners, who though their amps sounded pretty good before the service, are consistently amazed at the transformation.

Given the fact these caps have been operating for at least 16 years in a hot environment, and the owner places great value on the amps, it seems reasonable to have them serviced.

Herman: Hey, I need to get two vintage tubed guitar amps serviced for new filter caps (at minimum) right now. But I will say that most of the original caps in each of these lasted about twice Unsound's 20 years.

Porziob: The useless comments from you just keep on coming, don't they? Nsgarch wasn't responding to the threadhead in the post you criticized, he was addressing Joemt's concern from 8/2. It's a little thing called trying to help somebody, and pseudoscience wasn't involved. If you can only get your thrills from predictable negativity and weak sarcasm, the least you could do is take the trouble to read what you're attacking first.

To re-confirm the obvious, do replace those caps and also check other vulnerable components as suggested above.

I also VERY strongly recommend you find/purchase/otherwise obtain the SERVICE manual for your amps. Had you had that now, you could have changed caps (usually no big deal) yourself as well as checked all the tests points to see if anything else needs looking into.

Lastly, low voltage caps & resistors cost very little. Of course, the "safety factor" of having Harman service yr amps is very important; however, given a service manual, a competent & experienced electrician -- or experienced & knowledgeable diy friend could do the actual job just as well.

Get the Nuforce 9, listen to them about 20 seconds and you will decide the $2,280 to get ML20.5s up to shape is a real bargain!
I would check caps and resistors myself, not really brain surgery...