Mark IV strange noise troubles, HELP!

[jazguitardude92]

I got my Mark IV on eBay about 8 months ago, and just changed the tubes for the first time a week or two ago. I have noticed that when i turn on my amp there is a crackling noise then it turns into a siren like noise, almost like an ambulance or something. I don't know what is causing this. Could it be that i put in the wrong biased tubes, because i used all JJ's, or could it be because the tubes aren't in all the way? I am new to tubes and this is my first tube amp, so i don't know too much about tube troubles. Also, my Power tubes seem kinda loose compared to my old tubes, but i am pretty sure they are in all the way. Thanks!

 

[ANIMATED SUSPENSION]

Sounds like it could be a defective preamp tube. Try swapping one at a time with one of the old tubes. Does it work at all, or just make the funny noises ? I assume you got power tubes that are matched pairs, put them in the correct sockets (XYYX) and they are within Mesa Boogie specs ?

 

[jazguitardude92]

I got Matched Quads for Power tubes, and i got them from The Tube store online. i even got a matched sides preamp for the first stage. The Amp still works, its just that when i don't play it whines like a siren and crackles and stuff. Is there a way to check the tubes without taking them in and out, cause it took me a really long time to get the preamp tubes in since they are so far in the back. Also, when i ordered them i didn't realize that you could order specific tube ratings, so i just got any matched quad, so they might not be biased towards my amp right, but i didn't think that would matter so much cause some people mismatch that anyway for a different sound

 

[stokes]

Its most likely a microphonic preamp tube.While it is squealing pull out V1 and see if it stops.If so that is the problem tube.If not replace it and go to V2 and so on till you find the problem tube.

 

[jazguitardude92]

Its most likely a microphonic preamp tube.While it is squealing pull out V1 and see if it stops.If so that is the problem tube.If not replace it and go to V2 and so on till you find the problem tube.

Wouldnt that blow my fuse?, also, how do i get it out without burning myself from the hot tubes if it is still on?

 

[stokes]

Its most likely a microphonic preamp tube.While it is squealing pull out V1 and see if it stops.If so that is the problem tube.If not replace it and go to V2 and so on till you find the problem tube.

Wouldnt that blow my fuse?, also, how do i get it out without burning myself from the hot tubes if it is still on?

No,it wouldnt blow the fuse.How do you get it out without burning yourself?Be careful.In the combo,it is a little tricky,but it can be done.If you have a head,the front panel should come off to make it easier to reach the preamp tubes,but I've done it without removing the front.

 

[jazguitardude92]

Thanks strokes. I have the combo, but any tips on how to get the V1 tube out easier, since it is in the shield thing i have trouble lining up the pins with the holes

 

[jazguitardude92]

o wow, my V4 tube is glowing bright blue, and all my other ones are orange, is that probably the faulty tube?

 

[stokes]

The amp doesnt have to be on when you put the tube back in.If you have too much trouble getting the tube back in,you may have to pull a couple of power tubes to make access a little easier.Sometimes it helps if you lay the amp on its face so you can see the socket better.If you look carefully as you remove the tube,you may be able to line up the space between pins 1 and 9 relative to the little "dimple" on the sheild base.

 

[stokes]

o wow, my V4 tube is glowing bright blue, and all my other ones are orange, is that probably the faulty tube?

When you say V4,are you refering to one of the power tubes,or V4 in the preamp?A blue glow usually isnt a problem,but it is rarely seen in a preamp tube.If you have a MKIVA as you say,V4 is the reverb driver and recovery tube and can be eliminated as the problem by turning the reverb off and the squealing will stop,if so,then that is the problem.

 

[jazguitardude92]

ok, i replaced the fourth slot with a better tube, and most of the squealing is gone, but there is still a slight fuzz crackly sound that constantly comes out of the amp. It is a LOT quiter, but it is still there. any ideas? by the way, i have been laying on its side and i just removed the two inside Power tubes for better access, thanks for the tip

 

[stokes]

Is the squealing gone or just quieter?If it is gone and you are just getting the crackling sound,I would guess your tube sockets could use a cleaning and or re-tensioning.To test for that you rock the tubes in their sockets,one at a time,and listen for the crackling to increase/change.It could be caused by other things,but that is the easiest/first thing to check.

 

[jazguitardude92]

i meant V4 in the preamp, and i have a Mark IV a, it was the tube farthest to the left if your facing the backside. right now all the noises are gone and it is completely silent. Thanks so much, ill post in a day or two if it is still silent. O, and one quick question, is there any way to change the indicator LEDs, cause my lead channel is out on my amp. Thanks so much.

 

[jazguitardude92]

would you recomend returning my power tubes also to get ones that will match my amps biasing, i dont know how much it changes the tone, and i am just wonding if it would be worth the weight and 15% restocking fee. Also, i need to know which tube rating number i would need. Right now i have JJ's number 15.

 

[stokes]

To change the LED's you have to open the amp up and remove the bad one.It is dangerous inside a chassis and,meaning no offense,it doesnt sound like you have enough experience to poke around in there,as you said yourself,"I am new to tubes,and this is my first tube amp".You would be better off to find a tech to do it for you,LED's are cheap and an honest tech wont charge an arm and a leg to change one,but if you go in there and screw something up,it might cost you a leg.There are potentialy lethal voltages in an amp,even when it is turned off,so you could get hurt or dead as well.

 

[stokes]

would you recomend returning my power tubes also to get ones that will match my amps biasing, i dont know how much it changes the tone, and i am just wonding if it would be worth the weight and 15% restocking fee. Also, i need to know which tube rating number i would need. Right now i have JJ's number 15.

I dont use JJ's or any other current production tubes,I use NOS only,unless a customer insists on the cheaper current production,and in that case they supply the tubes and I just check the current draw to be sure they are okay.I am not familiar with JJ's rating system,but when you bought them did you request tubes that will "match" your Mesa amp?Where did you get them?When buying power tubes you should always get them from a supplier that grades them for use with Mesa amps.If you got them from a source that doesnt specifically sell them rated for Mesa,I would suggest watching the tubes while you play the amp to be sure the plates arent glowing red or orange.The plate is the large grey structure in the tube,dont confuse the glow with the normal point of orange light at the top or bottom,but look for a glow on the side of the plate itself.

 

[jazguitardude92]

how much will it effect the performance of my amp though, because if it isnt to drastic of a change, i am not going to worry about it, because i am still young and i am not using the amp for any serious gigs or recording sessions. however, i do want it to sound really good, i am kinda a tone freak for my age

 

[JOEY B.]

how much will it effect the performance of my amp though, because if it isnt to drastic of a change, i am not going to worry about it

How well do you like blowing fuses and a stinking smoke coming from your amp? Do what Stokes says, or just roll the JJ dice :wink: .