Mark IV distorted and popping.

[B.W.R. Audio]

I recently purchased a Mark IV the first version It was built in 1990. I love the amp but it started making a popping and crackling sound even if i unplugged everything thing from it but the speaker(unplugged reverb, fan, effects even tried different cab) it made no difference. Sometimes its really bad other times it stops within a few minutes. As of last night when i kicked it on for practice it was popping worse then ever and within in a few minutes it started sounding really muddy and distorted. It dosnt have mesa power tubes in it but there suppose to be new and they seem to look ok there JJ Tubes and there not getting overly hot or anything. I was planning on buying mesa power tubes as soon as i had the funds to do so, but dont wanna spend the money till i know theres no other issues. I have opened it up and everything looks normal the caps were replaced lasted year with mesa caps. I have also tried changing out preamp tubes one at a time with a good spare i have and it hasnt made any difference at all. Im fairly good at working on stuff like this but im a little intimitied by this one, but ive fixed alot of fenders some marshalls and other various amps. Theres just alot of stuff crammed in this one and id like to have an idea before i tear into it to much. Thanks in advance for any help.

 

[B.W.R. Audio]

Also i noticed that V2 preamp tube is flashing when i switch from R1 to R2. Thanks

 

[dodger916]

It sounds like a bad preamp tube, and it's probably the one that's flashing.

 

[B.W.R. Audio]

Thanks for the reply i should have put ive tested and swapped out all of the power tubes and tried to run down a bad preamp tube. I located the preamp tube i believe was causing the popping, but all of the channels are still muddy and distorted. So im wondering could it be a bad solder joint on a tube socket or possibly a short somewhere else? I love my Mark IV ive got to get it up and running this crap *** line 6 that im playing thru for shows just isnt cutting it. Im spoiled for my Boogie!

 

[sduck]

You say you've located the bad tube? Ok, now you've got to replace it. Just knowing which one is bad isn't going to fix anything. Before worrying about bad solders or whatever, try replacing all the preamp tubes with new ones or known working ones.

 

[B.W.R. Audio]

SDuck thanks for the reply but man theres no reason to be quit so condescending in your answers to people. Most of use are smart people who are looking for help from somebody who may know more then us or have more experience. It dosnt make them dumb so theres no need to talk down to people. If someones says they found there bad preamp tube and it hasnt fixed the problem chances are that thay have already replaced it. The bad preamp tube was obviously replaced with the correct mesa 12AX7. Fixed the popping didnt fix the the muddy problem. All of the channels still have a very harsh distortion to them? im actually thinking it maybe be some bad caps as i also found a problem with the wall plug in the studio weve been recording in. The wall plug wasnt grounded correctly and seems to have been shorting out and not grounded properly. Unfortantly it found it to late. Should have been using a power conditioner i know better and the studio should to lol.

 

[sduck]

Sorry man. I can only respond to what I read, and you did not say what you had done after locating the bad tube. All I knew was that you had determined which tube was the problem, and that you still had the symptoms. My bad for not reading deeper into what you were saying.

Have you been able to try the amp with a better power outlet?

Yes, at 21 years it's quite likely that the caps need some attention. I know mine probably do - my mark IV is a similar vintage as yours. Mine has some odd little nagging symptoms that suggest a major overhaul may be due, but it still works well enough to keep me happy for the moment.

So changing out that one tube fixed some of the problems, but not the muddiness - did you change any of the other tubes?

 

[jpdennis]

... Should have been using a power conditioner i know better and the studio should to lol...

Though not directly on subject of the muddy and the tube, I use a Monster 3500 power conditioner which works great. I also just read that Brad Paisley was having power issues even with his conditioner so his techs put an APC UPS in his rig which solved their power problem. Not sure if I am willing to carry any more weight with me where I go, but ... :lol:

Dennis