Mark V intermittent Noise issue

[Subjective Robot]

Hi Everyone,

First post here but have been a visitor for years.

I bought a second hand Mark V a while ago now, came with no name power tubes. Made in 2009, Serial number in the mid 2000s.

After a while it had volume fade issue so I completely retubed it (minus the rectifier) with mesa tubes (low noise 12AX7 in V1).

Everything was fine for a while, then this noise started:

https://youtu.be/gECM3bSPuno

I have searched here and elsewhere on the internet and have found others with the same noise, but nowhere has any confirmation of what the issue is.

I have had a local amp tech have a look at it, I think he was overwhelmed with it but he said that everything was ok with the amp.

I have bought an Orange tube tester which says all the tubes are ok (not sure if I trust it though).

I have tube rolled with known good tubes and the noise hasn't disappeared.

The noise isn't always there, but when it's there it's everywhere you want to be. All channels, all modes, all back panel settings and the sound is effected by what's in the effects loop.

Being secondhand and in the UK, I haven't contacted Mesa yet but will soon.

Have any of you had this issue with your Mark V?

Love it when it's behaving, but kinda stuck with it in its current condition

Any advise would be greatly appreciated

 

[jb's 52]

The last problem I had with mine turned out to be the last thing I checked/changed/swapped, the cable from my tuner to the amp.

 

[Eevil]

Hi,

does it make the noise without the pedalboard?

 

[Subjective Robot]

I'm 99% sure that this noise is present without my pedal board attached, but I will check to confirm this.

Thanks for the suggestions

 

[rarebitusa]

Ahh that noise sounds familiar. FWIW here's one datapoint... my V made a very similar sound which was greatly reduced by replacing the rectifier tube. Initially that sound was faintly still there, but only heard it when it was 1st powered on and after a few mins it was gone completely. Now as standard practice I just power it on and let it sit in standby for a few mins before taking it live. YMMV

 

[Eevil]

Ahh that noise sounds familiar. FWIW here's one datapoint... my V made a very similar sound which was greatly reduced by replacing the rectifier tube. Initially that sound was faintly still there, but only heard it when it was 1st powered on and after a few mins it was gone completely. Now as standard practice I just power it on and let it sit in standby for a few mins before taking it live. YMMV

If it actually is from rectifier tube one could test running the amp without the recto tube in 90w mode :shock:

 

[rarebitusa]

Ahh that noise sounds familiar. FWIW here's one datapoint... my V made a very similar sound which was greatly reduced by replacing the rectifier tube. Initially that sound was faintly still there, but only heard it when it was 1st powered on and after a few mins it was gone completely. Now as standard practice I just power it on and let it sit in standby for a few mins before taking it live. YMMV

If it actually is from rectifier tube one could test running the amp without the recto tube in 90w mode :shock:

yes this is true... full power mode

 

[rarebitusa]

Hey have to poke this thread again... cause I'm still dealing with the same intermittent noise issue that the OP outlined. It's never gone away completely, even though a Rect tube replacement helped alot a year ago. Recently the level of noise increased, which promoted another round of investigation.

First the current behavior.. on power up if left in standby for 15 mins before going live then there is no noise. However going live say a min or two after power-up, the noise is there and continues to be there for 30-40mins of playing but eventually will go away.

This noise is present on all chans and with any power setting 10/45/90, in diode/tube or tri/pent, reverb on/off, loop in or bypassed or full power or variac mode.

Have isolated the preamp using the FX loop send there is no noise there. With a jack in the Fx Rtn the noise is present in PA. Tube rolling V6, V7 and replacing the power tubes and Rect tube (again) makes no difference. Lightly tapping on any of the power tubes increases the noise substantially and with the same levels, there is not one tube that is noticeably different. Lightly shaking the head produces the same effect as tapping the tubes.

Next step is to pull the chassis and clean the tube sockets and look for anything obvious.

I've read thru a number of previous forum posts, which have been most excellent but any further suggestions on what to look at would be welcomed. Since I live close to Mesa taking it there is always an option and the service folks there are great. But want to ensure I've done my homework here first.

Thanks in advance.

 

[Slash_83]

Switching in that brutal way from 10w to 9o w and again back, is not never a good thing.

However, looking to your video, it could be a Cold welding, that after some little time start to make good contact thanks thermal expansion.

Otherwise a capacitor that is going to better life

 

[rarebitusa]

Well finally got around to pulling the chassis... no bulging electrolytic caps but a closer look revealed there was an unsoldered thruhole resistor leg on the power tube PCB @ V9. The leg was thru the PCB and it's side touching the plated thruhole but it definitely was missed in the soldering process. Touched it up and she's good to go now.

 

[rarebitusa]

FWIW here's the culprit

LHS is the before shot... left leg of the large carbon resistor

https://ibb.co/tsQJgzQ

 

[Subjective Robot]

Hey Everyone,

Thanks for the all the replies and sorry for disappearing, I had had enough and was ignoring the amp for a while but have finally fixed the issue.

It ended up being both the preamp V1 and a power tube.

The issue of the madness was rolling tubes always meant (for my ******* anyway) that the power tube and the V1 was always in the equation, and therefore always making this noise.

Anyway, it is now super quiet with no issues.

Hope everyone else here has managed to fix theirs!

 

[mace]

Glad you got it figured out! That was a hot mess of a noisy amp.