Marklll acting up

[marklll]

I have a Marklll black dot non simulclass combo that sounds slightly distorted on the clean channel regardless of the volume 1 setting. Could this be caused by a vaulty tube in V1 socket?

Any troubleshooting suggestions would be greatly appreciated.

Thanks

 

[McBarry]

Easy and "external" things to try are change V1 - any difference?
Change V5/PI - any difference?
patch lead in FX loop - any difference?

Rest of things involve working inside the chassis - let us know if U are comfortable/capable..
Caveat - if you don't know what you don't know about dangers lurking inside, don't go in there.

Good luck, DB

 

[marklll]

thanks for the information. Is V1 the tube that has the metal cover on it?Can you provide me with a link that shows the layout of the preamp tubes on the chassis?

Please advise,

Thanks

 

[Val666]

thanks for the information. Is V1 the tube that has the metal cover on it?Can you provide me with a link that shows the layout of the preamp tubes on the chassis?

Please advise,

Thanks

Yeah it is, changing tubes for the first time can seem daunting but it really is no different to replacing a light bulb! Check out this old thread, it should give you all the info you need http://forum.grailtone.com/viewtopic.php?f=27&t=38874

I suggest getting a new tube kit consisting of 5 preamp tubes and 4 regulars (just in case replacing the V1 doesn't solve the problem)

 

[MrMarkIII]

Does fiddling with the Reverb knob change anything?
If the reverb tank or the connection is acting up, the clean sound will be distorted and thin.
Just one more thing to check.

 

[McBarry]

If you're saying the reverb knob/reverb circuit affects your symptoms then yes, it may well be the culprit.
I would try and isolate the problem first, then go tube changing.
Don't worry about V3 - it's the lead channel.
Good luck, DB

 

[fretout]

I agree with the guys who posted ahead of me. V1 sounds like the issue, especially if the amp sounded fine before. You may also want to look into a SPAX7 of a 12AX7 with a lower noise floor. It could improve the tone you already know...