What to do with dead equipment

There is a major company in Boulder that accepts any equipment for trade in value

based on original MSRP.

I would simply note that if "this stuff worked great for 25 years" then you have indeed gotten the use out of it. If only everything else worked as long in our disposable civilization. Amortization of price versus the number of years you got out of them isn’t bad.

Sell them "as is" on eBay or part them out if you want to go to that much trouble to get a few extra dollars.

It is sad that BAT won’t repair it and give at least a 90-day warranty on that repair. With it being their design, they should be able to troubleshoot it and fix it. That was always the great thing about tube gear using discrete components instead of solid-state gear using integrated circuits.

There's a lady electronics tech on YouTube, goes by Skunkie Works, that often does videos and teardowns of Chinese made tube gear and others, and then she sees what, if anything could be better and upgraded for better sound and/or safety. 

She did a great series on the Willsenton R8 and R300. It looks like regarding the R8, the company took some of her suggestions and incorporated them. 

She might be interested (for a price) in seeing if she could repair it - and likely do a series of videos on why, how, and what she did. Just an idea better than dropping it off at Staples. 

Good luck.

Intermittent problems are the hardest to troubleshoot.  25 years of trouble-free use is good.  Probably retubing should have been done anyway.  About time to renew the capacitors too.  Either spend for repairs or spend for another.  This hobby is expensive.  Sell it inexpensively stating the problem/s that you are having.  At least get your money back for the retube.

You learned the hard way.  Preamps are notorious for unstable startups and power downs.  Can take out your power amp and or speakers.  Some mute its output on startups, but not all.  And their circuitry can fail.  Get into the habit of Turning On your preamp Before your power amp.  Turn OFF your power amp before turning off your preamp.

Sell it as is at a good discount in us audiomart. Get at least something for it.
Don’t just junk it.
 

Plant it in your backyard and see if a new one grows.