I bought a Fender Champ three years ago. It's from 1975 and has been modded so that it supposedly sounds more like a tweed Champ. Don't know what they did exactly but it sounds great and looks sweet.
I have had the same tubes in it for a year and it's going strong but I wanted to try something different. Tubes are really easy to change in a Champ. It is a cathode bias amp so you can just pop the power tubes in and out w/o adjusting anything. Supposedly, you can make adjustments in the bias of the amp and get it sounding better but I've never tried it and it seems to be working fine how I've been doing it. One of these days, curiosity will get the best of me and I'll go poking around in there.
Step one. Remove back plate w/ screwdriver:
They are Phillips head screws. You turn them counter clockwise to remove them. This exposes the tubes. You could probably just work around the cover but it'd be a pain. The Champ has three tubes in it:
From left to right, the first is the rectifier tube which is a 5Y3GT, the second is the 6V6 in the power section and the last is the 12AX7 preamp tube. Good stuff. So basically to get these guys out, you just grab hold and pull:
Be careful putting themin. You need to get the pins lined up. Power amp tubes have a little key that prevents you from putting them in the wrong way but preamp tubes you just have to be careful w/. Here is me putting a power tube in:
The one thing to be careful of is the tubes get hot if you've been playing. The rectifier tube swaps out the same way. I replaced it w/ the same kind, Sovtek, so it wasn't interesting enough to me to take a picture of it.
The particular tubes I tried were a reissue Tung-Sol 12AX7 and a JJ 6V6. I forget what kind of preamp tube I had in there but it was Chinese and sounded pretty good. I love the Tung-Sol though. Very tight sounding and clear but still very warm. It added a lot to my tone and I'm very pleased w/ it. The JJ power tube I wasn't so happy w/. It was slightly warmer sounding but in a muddy way that I didn't care for. To be fair, though, I am using a vintage Jan 6V6 that I got as NOS so the cards are kind of stacked against the JJ. NOS preamp tubes are way to damn expensive for me so I just go w/ new ones and have been fairly happy.
The other cool thing I did for my Fender Champ is build an adapter so I could plug it into a speaker cab:
It is very easy to build. You just need an RCA plug and a normal quarter-inch mono jack. To put it simply, you solder wires between them and you're done. I wrapped some of that shrink wrap tubing for wiring over the RCA to protect it. Couldn't really do much on the quarter-inch jack but it's held up for a couple years now.
The best part about this five-minute project is it allows me to do this:
I use a Weber Z-Matcher to match the impedances of the cabs to the amp. It is a wonderful device and very well built. Buy one. You'll find a use for it.
The two cabs I have going are a Traynor 4x10, which is a strange beast. It came w/ an old Traynor solid state head. The head and cab sound great together. But the head doesn't sound good w/ anything else and the cab is only so-so w/ other amps. I only keep it in my rig for the machismo factor. Say what you will but I like having a full stack in my living room and keep it as a matter of principle. The bottom cab is a Kern 4x12. It was made in the 70s in Chicago and is freaking awesome. It's my favorite 4x12 in the world. Kern still makes some bass gear now but their old stuff is super rare as far as I can tell. I actually sent them an email about this cab to see if I couldn't learn some more about it. Whoever I talked to was like, "Yeah, we used to make those," and that's about all I know about it. The speakers are some square-backed Eminence models and are beat to hell but still sounding good.
Anyway, that's about all I have to say about my Fender Champ at the minute. The silverface ones like I have are still pretty cheap and hands down better than the cheap little tube amps people are putting out now in terms of build quality. Tone is a matter of personal preference but I think this thing sounds better too.