E-Bay RETURNS, WHAT A BUCKET OF WORMS

I find out that if you buy a tuner or whatever on e-bay and open it up to put a tube or light bulb in , you have cancelled all your rights to return it......I buy a McIntosh tuner , open it up to replace the light bulbs and notice that my purchase is a piece of junk, I contact the seller and tell them I either need a adjustment or I need to return this........After 15 e-mails with the seller and e-bay about this I am informed that if I take the cover off I am a owner no mater what it looks like inside.......So be careful what you do if you want to return something.........ANOTHER INTERNET LESSON