I read the posts in this section but I never add anything, because I know less about amps than I do about women. So, with that in mind, here goes.
A few years ago I bought a Monoprice 15-watt combo tube amp with a 12" Celestion speaker in it and spring reverb (it even offers a 1-watt option, but at the level I play, there's really no difference). It was the basis for me running clean, and adding pedals to enhance the sound. Well, I never became the next Keef or Eddie, but it was fun.
Then it wasn't. All of a sudden it started to sound like crap. I couldn't figure it out. So, I put it away, and in its place I put either a Fender Champion 40 or a Fender Mustang II v2. As modeling amps, they are terrific, but since they have all the controls built-in, and solid state, I felt like pedals were superfluous.
Nowdays, I rarely play amplified, and if I want a quick practice session, I use either my Line6 AMPLIFi 30 or my new Positive Grid Spark MINI. They weigh less, take up less room and pretty much have all the features of the larger modeling amps (did I say I was inherently lazy?).
But over the years, I've read a lot of posts mentioning replacing the reverb tank; maybe they wear out, or go bad, or something, but I was wondering: Could this be the problem with the Monoprice? For the curious, I've been told this could be a "house-branded" Laney Cub, which goes for a lot more $$$.
Here's the web site for Monoprice's amp: https://www.monoprice.com/product?p_id=611815