Mark IV tubes

A-5best · Jun 29, 2009

Ok so Im starting to think my tubes are on the way out, my lead EQ tone is starting to get shrill and trebly rather than smooth, molten and thick and Im starting to get some feedback recently. I bought the amp used and the tubes were as well so Im thinking its time to upgrade.

Now, the thing is IDK jack about tubes. They say you really dont need to replace preamp tubes but would it be beneficial? I guess I should tap them and see if theyre microphonic right?

As far as power tubes, I want a set that will be able to do it all, beautiful cleans, rich slight breakup clipping and earth shattering distortion and molten leads. Admittedly I am more of a metal player but also like to play some other stuff so a balanced set with maybe an edge towards distortion would work. Being that IDK anything are there any tube kits that sound like they fit this preference?

Thanks

After poking and proding a bit it seems none are microphonic, but the amp is very loud when turned on with no guitar plugged in, a loud hiss is always present on the lead channel with some occasional cracking. It sorta looks like the preamp tubes might not be glowing but it is hard to tell, any tests I should conduct in order to pinpoint the problem

angelo · Jun 30, 2009

I have always had good luck changing tubes with Mesa tubes.

If you liked the "color" of your power tubes, get the same ones. I prefer gray or blue as I believe they give me the best cleans and overdrives.

When I was playing out a lot, I alos changed the preamp tubes once or twice a year depending on work load. More than many people would, but I felt good about it. Mesa used to have the 12ax7 SP for the input one slot - If they still do, I would recommend it for that spot. On the rest, I just use 12ax7's. If you want, you can change them one at a time till the hiss leaves. Then you know that one is bad and the rest are good for spares.

Retube and play the heck out of it! :wink:

A-5best · Jul 2, 2009

Thanks, is there any way I can switch tubes and figure out exactly which one may be failing in order to avoid buying a whole retube set?

Tuna141 · Jul 3, 2009

Most likely, it is only one tube that is causing you a problem.

If you want to try the cheapest solution: first buy one new preamp tube and then swap it with each preamp tube until you locate the one that is causing your signal degradation.

If they all appear fine, then try messing with the power tubes: Order 1 matched pair of power tubes (make sure you tell the store that they are for a Mesa amp) and swap the new pair with the inner pair. If the problem is still there, then try swapping them with the outer pair.

A-5best · Jul 3, 2009

Thanks thats exactly the answer I was looking for

A-5best · Jul 9, 2009

Ok so as I figured a tube just went and blew the fuse. Before it went I went into class A mode and it sounded like popcorn almost, even without a guitar plugged in, right before the fuse blew a tube was glowing, thing is I only saw the glow from its affect on my wall, Im not sure which tube it was. Is this type of failure a sign of power tube failure or pre amp tube failure? Any way to tell which one failed? If I was in class A it must be one of the outer 2 assuming its the power tubes right?

EDIT: Hmmmm after checking it out it looks like one of the power tubes went. So I guess I should just replace all 4 of the power tubes right? ****, now to figure out what to go with, Mesa, doug or eurotubes...? seems like Eurotubes doesnt offer too many sets without the preamp tubes included. A quad set from dougs is only 70 whereas form mesa it would be 84 altho Eurotubes does have a high gain set for only 66. advice?

Tuna141 · Jul 10, 2009

You can simply replace a pair of power tubes if you'd rather not spend the cash to replace all 4 power tubes right now. The 2 inner power tubes are one pair and the 2 outmost tubes are the other pair. If you were in Class when the tube blew, then the bad tube is one of the outer tubes. You need to replace both of them with a matched pair set to Mesa specs. Make sure you tell whomever you buy the tubes from, that they are for a Mesa amp.