Mark V Problem....help !

[stug345]

Hi All,

My MkV seems to have died last night......(on a New Years eve gig too !!)

The symptoms are: almost no volume at all, in any channel or mode, (it's pretty much inaudible), but will randomly give short loud bursts of volume.

I've changed the all the power tubes and swapped around a few of the pre-amp tubes, as I dont have any spares to hand.

Is this likely to be a tube fault or does anybody know of any other issue I should investigate? It showed no sign of breaking up or fading out, it just stopped.

I'd really appreciate any advice. It's my first Mesa, and apart from this fault, it's by a long way the best amp I've ever used !!

Thanks in advance

Stu

 

[screamingdaisy]

Sounds like a failed preamp tube.

 

[Jim Ed Love]

If playing professionally, you need to have spare tubes. Also, you should swap out old tubes after awhile, don't wait for tubes to go. You must have felt embarassed dicking around with your amp on stage.

 

[Barry]

Check this out.

http://mesaboogie.com/news/2010/11/mesa-amplifier-tube-troubleshooting/#more-1885

 

[domct203]

Are you sure it's not a cable/guitar issue?

Dom

 

[ATR1]

I had the same problem. Replaced all (7) pre-tubes and instrument cable. Works fine now. Focus on guitar cable 1st.

 

[stug345]

Thanks for the replies, advice, etc.

The amp sprang back into life today, but I'm not sure why. All i did was remove and re-seat the pre-amp tubes. I cannot get any spares till Tuesday.

However, shortly after that I lost sound on the 10w & 45w tube setting, which led me to the rectifier tube. I discovered that the glass tube is starting to break away from the plastic top part of the valve, so that obviously needs replacing, (I'd not removed it before).
But, it still does not explain why I lost sound on all settings beforehand. 90w & 45w diode are now fine.

I think I'll replace the rectifier tube and get some pre-amp spares ready and see what it does. I'd already tried it with a different guitar & cable, so had ruled that out.

And yes, I did feel a fool on stage on the gig, but thankfully it was on the last song it died, so I just about got away with it !!!

cheers

Stu

 

[stug345]

Hi,

I finally managed to replace the Rectifier tube after a huge delay with the postal system !!, and all seems well now with the amp

I've also purchased a spare and some spare pre-amp & power tubes.

Thanks to all who helped me out !!

regards,

Stu

 

[ixoye777]

Right on, glad you got it figured out Stu

 

[stug345]

Hmmm...After my somewhat triumphant last post my MkV Combo has died again. It’s back to intermittent sounds, worse than before

So after checking/changing everything once again, all tubes, cables, etc, I've decided to send it back.

It's a great amp with a great sound, but I think I need it checked properly, I feel I've run my course with trying to fix it, and I don’t fancy poncing about with bits I don’t fully understand and possibly make things worse.

It always seems to breakdown at rehearsals or on gigs.........never at home. Sods Law eh?

Cheers

Stu

 

[Rkorn]

That is a stupid and shi**y problem!!!
Could that have to do with volume???
I don't know where I have heard or read this but since you changed one tube and everything was ok...
Maybe you should change them all!!
as I have heard or read that once you find a problem in a tube you know that's the one... and that's all!!! That's the one with the problem, but you should change all of them!!

 

[stug345]

Yeah, I have changed them all. But I've got to the point that I'm sure somethings not right in the pre-amp. The rectifier fault I had was either a coincidence or I unkowingly damaged it removing the cage....who knows ??

I checked all the obvious, speaker connections, etc, but it has a mind off it's own. So I think it's best the shop handle it now.

I'll let you know the result..........at the risk of boring everyone to death

Stu

 

[rstewart2000]

Sounds like the same problem I am having. I just left a reply to another post from someone that seems to have a similar issue. I have mine in the shop, but the shop is having trouble replicating the problem. Very strange. The sound coming out of the amp is fine, it is just very quite. Turning the volume does nothing, then it will get loud all of the sudden, then after a few minutes quiet again. I'll post a reply if I get any answers.

 

[stug345]

Hi rstewart2000,

Thanks for your message....... I'll post any info I find out too.

My concern also is that the shop will not be able to replicate the fault and tell me it's OK, but I know it isn't !! Have to wait till they give me their results. It's a real pain of a problem eh ?

cheers

Stu

 

[Rkorn]

Well, mine was left at the store today... lets see what they can make of it.
The problem is not the same as yours... it makes this crackling and wind sounds... its not the tubes!! that´s for sure!
They say maybe a week, I have a gig by the end of next week also, if I don't have the amp i'm going to the store and they must lend me something else (in portugal a Mark V is only ordered in case someone pays it upfront)
I tell you my story once I know what has happened and if they fixed ir!

 

[stug345]

Hi,

Well, here's the update, as promised...............

My V is now back from repair. They say it was a speaker coil that failed.

So that all seems well now, but I appear to have a buzz with any overdrive, high gain on, which is irritating.

However, maybe I'm looking for a fault that isnt there ?? I'm sure it wasnt like that before, I remeber it being very quiet......... but after borrowing other amps for gigs, etc, the V is a distant memory now. I'm sure it's more pickuop/guitar related............I hope so.

Guess I'm going to have to try it on rehersal and see how it goes. Any ideas and advice would be welcome !!

cheers

Stu

 

[stug345]

Hi,

I think the buzz noise was me being too fussy. Tried it last night and volume and it's fine. I was just being paranoid !!

cheers

Stu

 

[wild_bill]

My new Mark V combo was only a few weeks old when I started having problems. Ch 1 sounded like crap. Ch2 was total distorstion and was popping. Ch 3 sounded too clean and was weak. I replaced one 12AX7 and Ch 1 sounded a lot better. Took it to the service repair shop because the other two channels were still real bad. Ends up I had a shorted JFET, a couple bad solder joints, needed two more 12AX7 and one of the wiring harnesses had to be rerouted because it was picking up noise. Amp sounds great now, but my Mark V head with 4x12 has it beat. Never had a problem the Mark V head and its a good thing had it so I could compare amps. In your mind you know it does not sound right but you always try to think its something you are doing wrong or something simple you can fix. Mark V is a great amp and I love it. I just got a lemon Mark V combo.

 

[stug345]

Hi wild_bill,

Mine seems OK now, I think I was looking for another fault that wasnt there.

so far, so good !!

cheers

Stu

 

[tofisi]

My new Mark V combo was only a few weeks old when I started having problems. Ch 1 sounded like crap. Ch2 was total distorstion and was popping. Ch 3 sounded too clean and was weak. I replaced one 12AX7 and Ch 1 sounded a lot better. Took it to the service repair shop because the other two channels were still real bad. Ends up I had a shorted JFET, a couple bad solder joints, needed two more 12AX7 and one of the wiring harnesses had to be rerouted because it was picking up noise. Amp sounds great now, but my Mark V head with 4x12 has it beat. Never had a problem the Mark V head and its a good thing had it so I could compare amps. In your mind you know it does not sound right but you always try to think its something you are doing wrong or something simple you can fix. Mark V is a great amp and I love it. I just got a lemon Mark V combo.

What JFET mean?