I recently undertook converting my Champion 600 from a SS rectifier to a tube rectifier. It took me a considerable amount of time of reading through websites and forum posts to figure out exactly how to do it, and I wasn't ever really able to find a simple "here's how to do it." Maybe I'm just bad at using Google, but I figured I'd type up a how-to to save others some time. I'm not saying this is 100% the way to do it, but so far it's worked for me. I'm sure someone will chime in if something is wrong. Before we get started, obligatory warning about tube amp voltages, make sure your amp is unplugged, the filter caps are drained, etc. The first thing I had to do was order a filament transformer. The stock power transformer didn't have any 5v taps. I ordered this transformer: https://www.tubesandmore.com/products/transformer-hammond-low-voltage-filament-open-5-vct Once the transformer arrived and was installed and the 5Y3 was wired up, there wasn't any DC voltage at the filter caps. After doing some investigating, I came across the "Hybrid Rectifier with No Center Tap" on Rob Robinette's page (https://robrobinette.com/How_Amps_Work.htm#Rectifiers) under the "all about rectifier circuits" section. After implementing this, I was getting DC voltage to the filter caps. Also if you're not sure, one primary wire from the filament transformer is soldered to the fuse, and one, in my case anyway, is soldered to the white wire that isn't coming from the power cord. In another post of mine, someone (I forgot who. I'll try to remember and check) recommended increasing the fuse by 500mA. I didn't know what to do with the center tap of the 5v Hammond transformer I had though. Initially, I tried grounding it, which was definitely not the thing to do, so I eventually just didn't attach it to anything. After doing some more searching, I came across this: https://www.thegearpage.net/board/index.php?threads/converting-to-tube-rectifier.2085288/ About halfway down the page, there's a post that says to connect the center tap to the first filter cap, instead of connecting the first filter cap to the pin of the rectifier tube. And, electrically, that's all there was to it. Some background information: My Champion 600 used to be the stock amp from whenever Fender "reissued" them however many years ago. I then modified it so it was closer to an actual Fender Champ. Eventually I modified it so much, I decided to do away with the PCB completely. The fact my Champion 600 didn't have a tube rectifier was something that was always in the back of my mind, which is why I decided to make the conversion. I made a hole for an octal socket between the existing preamp tube and existing power tube sockets. Originally, I planned on drilling a bunch of holes in the shape of the octal socket. After realizing it wasn't working, I ended up just using a jigsaw with a metal cutting blade. The result was a half circle, half square monstrosity, but the octal socket does an almost perfect job of hiding it. I then used the power tube socket for the 5Y3 and the new socket for the power tube. TL;DR Buy a filament transformer. Unplug amp, drain caps. Figure out how to make a hole for the new octal socket. Figure out where to place the filament transformer. Use hybrid bridge rectifier. Solder center tap to first filter cap, instead of attaching the first filter cap to the rectifier pin with a wire. Let me know if you have any questions, or, again, if something I've said isn't correct.