???Pre Amp Service???

if it sits in a box for more than 2 years, it's typical that it will work like a charm for two nights and then disintegrate into ashes like a Mission Impossible message.

I know that there have been threads on this very subject, and I remember some one advising that if a component was coming out of a long period in mothballs it was good practice to use a "variac" (I am not sure about the spelling) between the component and the outlet when turning it on for the first time. I assume that this is like a rheostat of sorts. If I recall, it was suggested that introducing AC to a component that had been sitting for an extended period of time might be better done slowly. And I do not remember if this pertained more to tubed gear than solid state. I believe I remember a comment being made that caps do not like to sit for a long long time not being charged and discharging, as I think it was said that they "dry out" over time.

But it’s too late for that, and apparently you experienced no catastrophic results.

From my own experience: from ’08 to late in ’10 I used my system rarely if at all. In late ’10 I took it down to put a new floor in the LR which was, at the time, my listening room. Late in ’17 I took it out of mothballs and everything worked fine. I have since upgraded all the electronics except for the (tube) amp, but today I am still using that amp that sat dormant for over seven years.  I remember the pre was noisy, but that was a bad tube or tubes and I replaced all of them.

I have another tube amp that had been sitting longer than my main amp, and in ’20 I fired it up when I was troubleshooting a signal cap on the main amp, and it did have a significant hum when I got it going.

I do not know enough about this stuff to say if the hum on the one amp came from sitting for a long time. As far as the bad signal cap in the main amp, I think I know what went wrong there and I do not think it had anything to do with sitting for all those years.

But if you did take your pre to a tech and get it checked and update, it seems to me as if that would be a selling point. At least I would see it as such if I was a buyer.

"if it sits in a box for more than 2 years, it's typical that it will work like a charm for two nights and then disintegrate into ashes"....
 Yea that's  my concern about NOT having it checked before selling..Problem is,can a tech tell if everything is really ok OR are there components I should just go ahead & have changed for new to assure reliability for a future owner?

I just now stuck an edit in there about my pre being noisy when I got it running again due to bad tubes, but that would not have been related to sitting.

Your question would be better answered by someone like @atmasphere ,as all I know how to do is make basic checks with basic meters (like a cap checker) and desolder and solder. I was told that the cap checker I have will not predict the life span remaining on a cap, and even if a cap checked good with my cap checker it didn’t necessarily mean it is a healthy cap. Only that if it checked bad, it was definitely bad. I do not know if a tech would have equipment that was sophisticated enough to verify that.

I’d say that if it is a real nice preamp and on top of that you had the film caps updated that would make it more of an attractive buy for some one. But I don’t buy and sell a lot (as a matter of fact, i don’t sell at all) so I do not know. Maybe get an estimate on that and see what it would run?

I started a thread, myself, inquiring about the life of the large electrolytic caps, and I seem to remember getting the idea that they held up better than film caps and I was okay. I was going to change them in my amp anyway, just because if one let go I felt it would be a nasty mess and they would be a breeze to replace in that amp being as there wouldn’t even be any soldering with screw in terminals, but that was a few years ago and i never got around to it and there have been no issues. That is a 23 year old amp and with the exception of one signal cap, there have been no cap failures.

EDIT:  OOPS!  I read your last post real quickly and I thought it was directed my way, and just now noted that it wasn't.  

When I did not used my art audio preamp and my audio research for 2 yrs . Ussully the volume tend to be affected. Maybe it gets dirty.I will have intermittent sound on both speakers. When I cleaned it, it goes away. Yes I start on turning on for 4 hrs then play the next day for 2 hours. I do in slowly.