Help diagnosing problem with my Mark V

[mva801]

Hello!

So My Mesa Mark V has been having an issue lately. On the first (clean) channel only, after about 10 minutes of playing, it starts cutting out. Almost sounds like a loose cable for a second, then the volume drops to almost nothing. The other 2 channels seem to work alright. I've tried three different cables and three different guitars.

Could it be tubes? Something else? The head is about two years old. It hasn't gotten a ton of use (mostly just sitting at the studio)

I'm sure it's due for a tube change anyway. And while we're at it, I haven't been too happy with the sound of the distortion channels lately either. Seems to sound thin and grainy. I usually play it out of a rectifier 2x12.

I'm a drummer so I don't know much about guitar amp problems. I know you guys can probably help before I go ordering tubes or calling the Mesa repair guy in my area.

Thanks for any help dudes!

 

[rispsira]

Hey man i dont want to guarantee that this is the problem since im not so good with technical issues, but i did have a similar problem (same head) where the volume would drop, and i would get some crackling.. i replaced V1 and it worked properly. Mine was new so you could still have tube issues regardless of the use; some just fail.

As to the distortion sounds i can help because mark series have a specific way of being dialed in if you understand the tone stack pre vs graphic post eq gain and what it means but of course as you already know the mark is pretty tight and that its character which will not sound as big as say a recto or 5150 no matter what you do. Im sorry as you probably know all that but i thought id mention it anyway.

Also what volume are u using? the character i find changes drastically as you turn the volume up (i know a lot of people say it can be used at bedroom volume with decent results but im not sure i really agree that much..)

 

[Sloan]

Swap around your preamp tubes and see if you can find a bad one. remember that 12ax7's are actually two triodes in one tube, so you can have one half bad and the other half good; it can be confusing as it might work great in one socket and not at all in another.

if you've got all known good tubes, then i would clean the tube sockets. spray contact cleaner on a tube's pins and then work it in and out of the socket.

if problem persists with known good tubes and clean sockets, check the suspect socket for loose contacts. http://billmaudio.com/wp/?page_id=171

 

[MatrixClaw]

Usually, I'd say it's a power tube problem (volume drops are almost always a sign of needing to change power tubes) - But if you're only having that issue on the clean channel, it's likely a preamp problem.

 

[mva801]

Well I replaced the V1 with the Mesa spax-7. It sounds better. The crackling seems gone and channel one didn't cut out when I played it. But the distortion channels still sound like ass. I fired up a brand new Mark V at the guitar store, and it sounded amazing. BIG difference between mine and a new one. There's still something else not quite right.

Maybe I should replace the power tubes as well? I'll also check the pre-amp tubes. Videos on Mesa's website say to turn on the amp and gently tap them with a pencil eraser and see if they make noise. I may try that. I got all excited again when I played the one at the store. It sounded great from the start.

 

[Sloan]

Videos on Mesa's website say to turn on the amp and gently tap them with a pencil eraser and see if they make noise.

That's to check and see if they are 'microphonic'. Typical symptoms of microphonic tubes are uncontrollable feedback like howling noises when you aren't even playing anything.

Microphonic problems usually appear in the form of a ringing or high pitched squealing that gets worse as the gain or volume is increased thus are more noticeable in the higher gain Lead modes. Microphonic problems are easily identified because the problem is still present even with the instruments' volume off or unplugged altogether - unlike pick-up feedback which ceases as the instrument is turned down. Microphonic noise is caused by mechanical vibration and shock: think of banging a microphone around and you'll understand where the word came from.

 

[mva801]

That's to check and see if they are 'microphonic'. Typical symptoms of microphonic tubes are uncontrollable feedback like howling noises when you aren't even playing anything.

Ok. That doesn't seem to be the problem I'm having. It just sounds like shit compared to the new one. The distortion is very thin and grainy sounding. There's something really annoying going on in the high end. I'm getting kind of a weird buzz that's constant. Doesn't sound like a normal bit of hum.... it's kinda.... weird.

I know certain preamp tubes are exclusive to specific channels. Would it be more prudent to start looking at those, or replacing the power tubes first?

Thanks for the help guys!

 

[MatrixClaw]

TBH, if it's 2 years old, I'd just replace them all. To me though, it sounds like you're having issues with the preamp tubes, however, since you still have the stock tubes in there, once you replace them all, it should sound better than the one you played in the store.

 

[mva801]

Bumping this thread rather than make a new one. Was talking to the Mesa rep I know a bit ago, and he sent me out a full set of brand new tubes for my Mark V. Pretty awesome.

So now the issue. I go to swap the tubes. When I get to the V3 preamp tube, it has two wires soldered to the pins of the tube. They've bent two pins on either side and there are two yellow wires soldered to it. So obviously I'm not going to muck around with switching that out. Anyone have any ideas why they would do that? And I'm guessing I'll have to take it to a tech to have the tubes swapped?

Couldn't find any info on that in the manual or on the boogie sites.

 

[Sloan]

Bumping this thread rather than make a new one. Was talking to the Mesa rep I know a bit ago, and he sent me out a full set of brand new tubes for my Mark V. Pretty awesome.

So now the issue. I go to swap the tubes. When I get to the V3 preamp tube, it has two wires soldered to the pins of the tube. They've bent two pins on either side and there are two yellow wires soldered to it. So obviously I'm not going to muck around with switching that out. Anyone have any ideas why they would do that? And I'm guessing I'll have to take it to a tech to have the tubes swapped?

Couldn't find any info on that in the manual or on the boogie sites.

Can you post a pic of this?

 

[thefalloftheheretic]

This is just hazarding a guess, but I reckon that the wires mean that whoever had it before you had grounding issues.
Take it in and have it worked on.

 

[ArthurD]

I had a similar problem, and I resolved it with a cable test.
I had 5 BAD CABLES. Couldn't believe.
Bought Monsters.

 

[mva801]

Can you post a pic of this?

You can see some of the pins bent up and soldered onto these wires.

This is just hazarding a guess, but I reckon that the wires mean that whoever had it before you had grounding issues.
Take it in and have it worked on.

It came from Mesa this way. They sent it to a band we were recording as a review piece, and I got hooked up with a good price by their Mesa Rep. It's serial number 13. I know for a fact nobody has touched the tubes or inner workings since Mesa shipped it..... The band had it for a week, and it's been sitting in the studio and or my bedroom for the last two or three ish years.

So weird.....

 

[bryan_kilco]

You can see some of the pins bent up and soldered onto these wires.




It came from Mesa this way. They sent it to a band we were recording as a review piece, and I got hooked up with a good price by their Mesa Rep. It's serial number 13. I know for a fact nobody has touched the tubes or inner workings since Mesa shipped it..... The band had it for a week, and it's been sitting in the studio and or my bedroom for the last two or three ish years.

So weird.....

wtf.....

 

[rispsira]

yes it is weird, mm sorry dont really have any helpful advice but id say definitely take it to a technician to check it out

 

[Sloan]

Yeah, that's strange.

 

[mva801]

Balls. Well my Mesa guy hasn't responded to my email yet. I'll send him the same pic. Guess I'll look up the Mesa authorized fixer upper guy in my area and give him a call.

Thanks anyways guys. I'll report back when I figure out what the hell those are doing there!

 

[sprack]

If I'm seeing the key pin properly then it looks like he wired straight to the heaters. Why he'd do that I can only guess. Maybe a bad trace he didn't want to hunt down or even lazier he didn't want to remove the board and just direct wired it rather than correcting it at the socket. That's craftsmanship.

Ja, get that to a tech.

 

[MatrixClaw]

That is definitely NOT normal on Mark Vs.

I send gear to my friend who runs a shop in Russia and we have ordered numerous, brand new, Mark Vs and I always pull the tubes and wrap them up before shipping it out. I've never once seen that on a stock Mesa amp. I guess it's possible they did it since this was a test unit, but I honestly have no idea why they would even think to do something like this.

 

[greyskull]

Wow... That is a right bodge.