Princeton Reverb - likely reasons for "farting out"?

[Leo_Gnardo]

Unless "Genuine Fender" Illinois caps were used for the clone.

Aw c'mon, Ill-noise can't be all that bad, should last 4 years anyway. I haven't seen any go bad before they're 8 years old anyway...

But seriously, I'm thinkin' your harp playing friend may have given your Princeton output tubes & speaker a helluva workout over the time he had it. It's like lending out a car for a year, you have no idea what it's been put through, driving over rocks, hauling tons of chicken manure or what. You don't have an odometer on your amp to see what mileage he put it through. And you have no idea what "third parties" may have had access to it and also put a hurtin' on it.

Some people don't have any respect for what they rent or borrow.

I bet you won't be lending out any of your amps in the future. Cue Alice Cooper "No More Mister Nice Guy."

[Chuck H]

I once lent out a car to a friend. She was turning things around in her life and needed to get back and forth to work. It was a spare car at that time and it seemed like a worthy sacrifice. It was actually. She's more successful now (some twenty years later) than any of my other friends/acquaintances (probably combined). But... She had the car for about a year and put 17,500 frickn' miles on it! And there was a big hole punched in the head liner :-/ Oh well. I love her her and she proved her intentions by continuing to prosper. But Leo's right... You just don't know until you know.

[Tom Phillips]

I have loaned out amps. However, the deal was that I always brought the amp to the venue, stayed for the show and the took the amp home with me. My personal rule was to never ever let my equipment out of my sight. Never ever!

[Justin Thomas]

Luckily, most of the guys who want to use my amps are either too weak or too lazy to carry a 30-90lb amp away with them...

Justin

[Chuck H]

Yeah, that's a funny thing isn't it. Some people know I'm a handy guy with tools for a lot of different, odd crafts and chores. They may ask to borrow something. If I happen to be right there, or will be, I'll usually say yes. Sometimes they see my clunky, heavy and old $h!t and say "Nah. That's alright."

[The Dude]

I was doing some studio tracks years ago and needed a keyboard. A bar owner friend of mine had a Yamaha DX7. I called and asked if I could borrow it for a day. He told me no problem- come and get it. I got there and it was in a case built out of 2x4's and 3/4" plywood. The case was ridiculously heavy. I asked him why he built such a heavy case. He said he did it so people wouldn't want to borrow the keyboard. I left the case at the bar and took the keyboard.

[Familyortiz]

Like Justin said, start with checking each tube, one by one, with a known good pre and power tube. This will isolate tube issues.

[potatofarmer]

Honestly that sounds about right for a blackface clone. Typically they reach full output at around 4 on the volume knob and fart like crazy is the bass control is above 3 (depending on the guitar, of course.)

Harp players tend to want early breakup, so I'd check and see if any of the tubes have been swapped with other types.