Riddle me this…MT15 issue

[Rusty Shackleford1111]

I’ve tried searching for this problem and haven’t found any info.

I usually leave my MT15 on half power setting, all of the sudden the sounds started cutting in and out and making crackling noises/sound cutting in and out etc..

After some research I decided to try swapping a new 12ax7 into each position at a time starting with v1. Didn’t work.

I switched the amp to full power and it works normal.

Anyone have any ideas what could be causing this issue on only the half power setting?

 

[sergiodeblanc]

Wonky power tube.

 

[Rusty Shackleford1111]

Wonky power tube.

Thanks for the help. This is my first tube amp and I’m still learning.

Of course, it’s the one thing I didn’t try lol.

Can you recommend a particular brand? Affordable but still decent?

Also do you think I should do an exact replacement of the 5881, or should I try 6L6 instead?

 

[Bogner]

Do you have to run the amp at half power? 99% of tube amp issues are tubes or fuses. If your tubes are not shot I would simply leave them alone. All tubes right now are expensive and are a crap shoot on how long a particular tube will last. There are so many variables. Just like light bulbs, there is no guarantee how long they will last and if the "set" of tubes will last equally from tube to tube within the set.

Regarding tube type, the 5881 is known to be very dependable and predictable which is nice for an amp maker. They are pretty fault proof in most cases. That is only one side of the coin. The other side is how a tube sounds within the amp. While there may not be a huge difference there are differences nonetheless. What a person gravitates towards is their personal preference and there is no right or wrong answer for what you like. That said, for this particular amp, both tube types sound wonderful. Unless you have money to burn on tubes, I would leave them stock until it is time to replace them and then at that point make a decision. I have 6L6's in mine but when the time comes to replace them I will most likely use the set of 5881's I have in my tube stash simply because I already have them and they do sound nice in my friends amp so I know I will be pleased with such a change.

Regarding pre amp tubes...you will get more variance in this tube section in regards to little tone tweaks and by using various brands of 12AX7, etc tubes. V1 will be the most dramatic change...V1 is the closest tube in relation to the input jack where you plug your guitar cable into the amp.

Back to the full power aspect. I can crack my volume on full power enough to where it is very quiet and fine for bedroom or late night playing, etc. Pots are touchy and each one has its own sweep but there is a place you can get it to where it should work fine on its adjustment to get you a proper sound at a lower volume level.

I hope some of this info helps.

 

[claythomas]

I'm a big fan of Mesa's 5881's. Sound great, durable, and consistent.