My amp breaks up too much and sounds messy. I changed the tubes and resistors and it helped a little but didn't solve the problem. Could it be my speaker?

you could have blown a resistor or transistor since it's not a tube amp.

change out pre amp tubes

Flick your finger nail against the preamp tubes. This will tell you if any are microphonic which most likely the case. It usually takes a few minutes for them to begin squealing.

Usually the amplifier will have "symmetry" and there will be matching resistors near the other power tubes that you can get the value from. This is PROBABLY a screen resistor for the tube and values are often around 470 ohms or so but I could not find a schematic. These USUALLY don't fail unless a tube has shorted. Heat sinks are NOT used. The best resistors for the purpose are "wire wound" ones and of a suitable wattage rating. Sometimes we put ceramic beads on the leads to raise the resistors off the board to allow air circulation. Occasionally solder will break and the arcing at the leads adds to the heat. If you trace where the resistor goes by pin number of the tube and the type of the tube that would help me to help you... trace a matching tube to the same pin and you will likely find a matching resistor. Note that some power resistors DO change color a bit after they get hot in use, but if they char or the coating falls off that is a failure.

your parallel loop only has input, a series has out and in, you need to patch the out of amp to the in of the pedal, and out of the pedal to the in of the amp fx loop. then you need to make sure your loop is turned on, via switch or footpedal.

If it worked before you changed the tubes, it is possible one of the replacements (probably a small tube) was bad... it happens... Another possibility is that a socket pin has gone bad or a pin has broken or bent off... again probably one of the small ones... 12AX7/12AT7 or equivalent.
Swap old ones back in one at a time.

Fender hot rod´s have an common problem on the plate resistors of the preamp and phase inverter tubes.

Check if the 100K and 82K resistors on the tube socket board are not brown. Those resistors usually need to be changed to bigger ones 1/2W.

this guy made a good document about this fix:

http://home.comcast.net/~fredholz/Justin-Holton/Fixing%20Loud%20and%20Intermittent%20Crackle%20or%20Static.pdf

i am guessing on what the problem is , the post is very vague. i am guessing a channel switching issue. you need to check the "sugar cube" looking power resistors solder welds. they are probably cracked and arent making good contact. if you tap on the amp it will cut in and out, its probably these two resistors. they are usually 470ohm 5 watt cement resistors. what happens is they get real hot, and as they cool down they crack the little solder welds. i usually replace them with new and keep them floating up over the pcb to help them stay cool and off of the board to prevent further solder weld cracking, stock they are real close to the board. then put a little silicon under the resistor to hold it in place and to keep it still on the board. i just fixed a blues deluxe with this issue. while you are in there, cut out the resistor sitting right behind the reverb pot, this will make the reverb awesome. also solder the mid pot center leg to the mid pot leg that comes off of the bass pot leg to get better midrange control. very easy mods. check the master volume pot, is it a B100K? pull it and put an A250k in its place for better volume control. bias pots , etc. check my website yostamplifier.com.

The 12AT7 is usually the driver tube for the tubes before it ( the input channels ). It can also be the driver for the reverb or tremelo channel. I'm not sure what model of amp you have or the manufacturer but there are plenty of places to look on the internet for info. http://duncanamps.com/index.htm is a good place to start. If you can't find the schematic for your amp try and find one that is similar to give you some ideas. If you don't have the basic tools like a volt/ohm meter and a capacitance tester. You might have to consider a pro to look at it. You will be looking for resistors and capacitors in the same circuit as the tubes that you originally mixed up. If its a hybrid solid state/ tube amp you will also need a transistor tester. Of course good soldering abilities are necessary and ABSOLUTELY do not work on the amp while it is plugged in and make sure you properly discharge the filter capacitors in a safe and proper manner before touching the circuit. All the info you need to sucessfully do it yourself is available at the library or on the net as long as you are confident in your abilities and first and foremost work in an absolutely informed and safe manner. Hope this helps.

Ah yes: complete catastrophe. Usually when everything is not working, it is a single reason and when that single reason is fixed, so is the amp.

Based on what you tell me, I am going to say you have a bad power tube. And I will even go as far to say that you buy a set of tubes and play on them as long as you can. If so, then you not only burned up the tube, but weakened the power section and may have a slooow tube frier. I always tell customers: modern tubes have an effective life of less that 1200 or so hours and that varies. Replace the tubes once per year if you gig with the amp: period. Otherwise, guys like me (doing repairs) stay busy and the tube companies get rich selling tubes to amps with weakened power sections.
It sounds like you burned a power tube and blew a fuse. First, you need a new set of power tubes and some extra fuses (go to Radio Shack and set the value you need in SLOW BLOW fuses).
Then, replace all the power tubes. Don't worry about biasing yet, we are just seeing if there is a problem. Next, replace the fuse.
Turn on the amp and play on it at various volumes and settings. If all is well, take the amp to a tech and get it rebiased. If you can afford it, pay to have the grid/plate and other resistors changed so the power section will be like new (clean slate with new tubes). Your amp will love you for it.
Almost all of the amps I have worked on for performance problems (cant keep tubes to stay alive for very long) are directly related to end user use. When you use a tube until it blows it ALWAYS TAKES SOMETHING WITH THE TUBE WHEN IT GOES (like the power section components). The compents will be weakened and the tubes will 'wear' at different rates that can even move them out of the 20% tolerence they must be within to sound good. 99% of the time a board repair with a retube after a catastrophe fixes the amp until the next time it is 'run into the ground'. Tube amps are NOT invinceble: they are weak compared to solid state and expensive to own. But we love tubes because they sound great. I have solid state to knock around on, when when it counts, I play only with tubes. I have spent hundreds on good tubes because you do get what you pay for.

Hope this helps!
-mike