Mark IV crackling noise

[jace]

I need some help guys, my mark iv has been making a crackling noise and I cant pin it down to which tube or tubes are making the noise. The tubes are all about 6months old, except the 2 6l6 outer tubes, which were replaced in september. I replaced them because I had el34s in and 1 went bad making the same crackling noise that im getting now. The crackling noise isnt always there though, the last time it did it was about 2months ago but it started again today. It does it on all 3 channels, most noticeable on r2 and lead channels though. Any advice on what it might be would be appreciated?

 

[swbo101]

It sounds like a power tube for sure. First I would try switching it to class A..Do you still hear the crackling? If so it's the outer tubes. If you only hear it in Simul-Class then it's the inner tubes. That's what I would try next.

 

[jace]

I tried that, it still crackles just not quite as much when switched to class A. So I guess I need to replace the outer tubes again then. If thats the case could there be some other issue thats causing the outer tubes to fail so quick? The reason I ask is because I bought the amp in august, all the tubes were only a month old when I got it. Then 1 of the outer tubes went out in september and now again just a few months later. Could it just be bad luck with the tubes or somethin else causing them to fail?

 

[littlephil]

I had a similar crackling with my Mark IV, it would come and go quite often. It was a preamp tube, I had JJ's in there, and I was going to replace them, so I got some NOS RCA's from ebay. After I replaced them the crackling was gone completely (and the whole amp sounded much better too!)

I'd do the microphonic tube test with a pen/pencil, you might not find a microphonic tube, but it won't hurt to test them anyway before you go replacing anything else.

 

[jace]

I tried the test and all the tubes are quiet. I tapped on top of the head lightly when putting the pencil down and it crackled, and the crackle was there on all channels, tried both class a and simul class and still there. I tapped the head lightly a few more times to see if it would still do it and it did. So still an outer power tube or what?

 

[swbo101]

When you did the pencil test on the pre-amp tubes..how did it go with the V1 tube? I would concentrate there. Maybe just try replacing the V1 tube with a spare if you have one.
As far as the power tubes what do you have in there (brand) currently?

 

[topcat0399]

or perhaps dirty pins/sockets.

Pull the head out of the cab - its very simple to do; I do it regularly (takes about 3 minutes).

get a can of electronics cleaner; pull every tube and hit the pins with the cleaner.

I also hit all the socket contacts with the cleaner.

Then insert and pull 7 or eight times each tube in and out of its socket (to clean the contacts in there).

Sometimes it also helps to re-tension the socket contacts - I use an ice pick for this.


Good Luck man - Mark IV's ROCK.

 

[swbo101]

or perhaps dirty pins/sockets.

Pull the head out of the cab - its very simple to do; I do it regularly (takes about 3 minutes).

get a can of electronics cleaner; pull every tube and hit the pins with the cleaner.

I also hit all the socket contacts with the cleaner.

Then insert and pull 7 or eight times each tube in and out of its socket (to clean the contacts in there).

Sometimes it also helps to re-tension the socket contacts - I use an ice pick for this.


Good Luck man - Mark IV's ROCK.

This is a excellent idea to try. Just please be sure NOT TO TOUCH the capacitors after you pull the head out. There maybe enough juice there to shock you really bad.

Good call topcat.

 

[jace]

When you did the pencil test on the pre-amp tubes..how did it go with the V1 tube? I would concentrate there. Maybe just try replacing the V1 tube with a spare if you have one.
As far as the power tubes what do you have in there (brand) currently?

V1 was quiet also, could hear the tapping a lil more but thats all. I dont have any spare tubes right now I need to order some. All the tubes are mesas.

or perhaps dirty pins/sockets.

Pull the head out of the cab - its very simple to do; I do it regularly (takes about 3 minutes).

get a can of electronics cleaner; pull every tube and hit the pins with the cleaner.

I also hit all the socket contacts with the cleaner.

Then insert and pull 7 or eight times each tube in and out of its socket (to clean the contacts in there).

Sometimes it also helps to re-tension the socket contacts - I use an ice pick for this.


Good Luck man - Mark IV's ROCK.

What type of electronics cleaner do you recommend?

 

[topcat0399]

When you did the pencil test on the pre-amp tubes..how did it go with the V1 tube? I would concentrate there. Maybe just try replacing the V1 tube with a spare if you have one.
As far as the power tubes what do you have in there (brand) currently?

V1 was quiet also, could hear the tapping a lil more but thats all. I dont have any spare tubes right now I need to order some. All the tubes are mesas.

or perhaps dirty pins/sockets.

Pull the head out of the cab - its very simple to do; I do it regularly (takes about 3 minutes).

get a can of electronics cleaner; pull every tube and hit the pins with the cleaner.

I also hit all the socket contacts with the cleaner.

Then insert and pull 7 or eight times each tube in and out of its socket (to clean the contacts in there).

Sometimes it also helps to re-tension the socket contacts - I use an ice pick for this.


Good Luck man - Mark IV's ROCK.

What type of electronics cleaner do you recommend?

I dunno - any thing "fast dry" and "no residue". Sometimes I get some at auto parts stores, sometimes at place like radio shack.

You can discharge your caps by playing a chord on a guitar as you shut the amp off.

 

[jace]

I will give it a try this weekend and see what happens, hopefully it does the trick. If not I guess I will have to order some tubes on Monday.

Just played on it and tested it again, no crackles at all. So idk whats up with it. I'm still gonna buy some cleaner 2nite and see what happens.

 

[McBarry]

Don't wanna rain on the easy fixes, but I've had crackling in 2 amps..
First one (Kity Hawk M1 head) was a leaky coupling cap, letting a little DC through. Replaced. Sorted.
Second one (Boogie MkIIA) was crap on the board - allowing DC between tracks. Cleaned with solvent then metho. Quiet as a mouse. Very easy fix, but was a bugger to find and I acknowledge working with a live board is not for everyone.

 

[jace]

Don't wanna rain on the easy fixes, but I've had crackling in 2 amps..
First one (Kity Hawk M1 head) was a leaky coupling cap, letting a little DC through. Replaced. Sorted.
Second one (Boogie MkIIA) was crap on the board - allowing DC between tracks. Cleaned with solvent then metho. Quiet as a mouse. Very easy fix, but was a bugger to find and I acknowledge working with a live board is not for everyone.

Did it crackle constantly or just every once in awhile? I havent tried the cleaner on it yet, but it hasnt crackled since Thursday.

 

[McBarry]

Hey Jace,
the cap was pretty much constant crackle, intensity varied a little. Not a "horrific" noise and not audible against the band, but present none-the-less..
Board contamination betweent tracks was very much from powerup and declined to zero over about 4-5 mins. Of course, if U left standby OFF in this time U would miss hearing the noise, but it was easly detectable and measureable with a fine tip DMM probe.
One source was undetermined, but another was me -I eventually discovered the flux had been used on a plumbing job - some of the plumbing flux contaminated my electronics flux - pitfalls of lending out your gear I guess..
With lights turned off, I've seen old Fender boards lightly arc between tracks on power-up. No pyrotechnics, but just visible.

 

[Waspination]

I have this crackling issue too, but it seems to be something that when the amp vibrates enough from playing too loud... it breaks up badly. My buddies dad is gonna look at it cuz he did tech on amps for a living but i wonder what it is...Class A seems to make it worse... All i gotta do is tap the amp itself a bit and i crackles so i cant pin point a tube.

 

[jace]

Heres an update. Well I ended up taking the amp to get repaired and it was a broken power tube socket. I have had the amp back for a few days now and it sounds better than ever. The tech said since it was broken the 1 power tube prob wasnt functioning all the time just going in and out. When I did the pencil test right before I took it in I was getting noise from only that tube socket and when it crackled I also noticed a change in the glow of that 1 tube. So that would make sense.

 

[topcat0399]

Heres an update. Well I ended up taking the amp to get repaired and it was a broken power tube socket. I have had the amp back for a few days now and it sounds better than ever. The tech said since it was broken the 1 power tube prob wasnt functioning all the time just going in and out. When I did the pencil test right before I took it in I was getting noise from only that tube socket and when it crackled I also noticed a change in the glow of that 1 tube. So that would make sense.

as successful low cost simple repair is always a happy ending.

Rock On!

 

[McBarry]

But even better, is that after a few months U wrote a followup, showing the cause/solution.
Great stuff.
Just out of interest, did he say what was actually broken about the socket ie: dry joint, broken incoming wire, broken pin socket etc etc..??

 

[jace]

it was a broken solder joint on pin 8 of tube socket. And my amp is still under warranty so the fix was free

 

[McBarry]

Cool, glad it was a simple fix, and "free" also helps..