FWIW, 5y3 is a kinda wimpy rectifier in specs to begin with. Think if you stuck in another one it might be prone to crap out again. You might have a lot better luck with a decent vintage old stock 5v4, they are not too much more expensiveand are capable of handling higher output demands than 5y3. If LSS means Lone Star Special, it's a 4-el84 tube amp, right? Have run 5v4 in my Maverick for hundreds of hours with zero issues, that amp calls for 5ar4, a slightly higher spec for output than 5v4. 5y3, 5v4, 5ar4 all have 2 amp heater current draw and identical pinout to the socket. Maverick runs 4 el84's Class A and is basically Lone Star Special's Daddy. I have had great luck with vintage Sylvania 5v4, GE 5v4, and Westinghouse labeled Syl 5v4, should be easily available for less then 20 bucks each on ebay. Best of luck to you!