Mark V tone issue

[MarkV User]

Well hey there, I can see what you are talking about and I do see one thing that looks wrong to start with. Are your channel 2 and 3 LEDs both lit up at the same time when you are in channel 3 mode?

If that is the case then yes something is probably broken. Possible culprits are the low voltage diodes and the footswitch or its cable or the channel switching “logic” it controls in the amp. Some of the JFET switches controlled by the modes may also be burned up.

And also you didn’t tell us what line voltage and line frequency you are using and make sure they match what the amp needs. There is a note next to the fuse in the back. I think Thailand has 240V/50Hz at the wall which would be a big surprise to the Mark V. If you are using a power converter then make sure that is not the source of the problem.

If you have to make a series of repairs make sure of the power first and find out what has been done to the amp to make it work on 240V / 50Hz if that is the wall voltage you have. Make any corrections needed. Then replace the low voltage diodes, preferably with diodes that have a higher current rating. Then look for the other problems.

Not All of this applies if the simultaneous channels are somehow an optical illusion

You may be able to get some information on your amp by contacting Mesa Boogie. I don’t know. Good luck!

 

[user 85366]

Hi Mark V user, unfortunately it is an optical illusion, I might going to see a tech this weekend, the voltage has been set up at the right voltage 240/50hz I think when they sell Mesa amps new, they are already set up for that specs as the previous owner told me, he bought the amp new and also 3 technicians had already inspected it, if that was the case they might have noticed that hopefully. I will keep you updated, thank you!

 

[danut]

I see what you mean, the 2nd and 3rd channels seem to be lacking, a bit, in the saturation department (but it also depends alot on the output of the pick-ups, too! For example, I can't believe how much less saturation I get with my Les Paul Traditional, equipped with '57 Classics, compared to my Les Paul Custom, equipped with 490R/498T! It's almost like I'm playing two different amps!).

Other than that, there is, however, one little thing I am not comfortable with, when it comes to your settings: the way you balance the Output with the Master sections. IMHO, with the Output at 2 o'clock and the Master barely on, you have them set them pretty unbalanced. I would like to hear your samples played again, with lower Output and higher Masters (keeping both Output and Masters in the 9-11 o'clock region).

 

[user 85366]

Hi Danut,
I got your point, I've plugged in different guitars from Ibanez, Fender, Ernie ball, but not much difference also when you set the output on 9 -11 it rises up the volume with more room but not many changes about saturation, it gets even worse.

 

[rarebitusa]

Hi Danut,
I got your point, I've plugged in different guitars from Ibanez, Fender, Ernie ball, but not much difference also when you set the output on 9 -11 it rises up the volume with more room but not many changes about saturation, it gets even worse.

Curious have you tried disabling the fx loop which bypasses the master volume out to see if there is any change in tone?

 

[user 85366]

Curious have you tried disabling the fx loop which bypasses the master volume out to see if there is any change in tone?

Yep I did not many changes it might be something related to caps or diods or the voltage on the plates I will contact another Mesa tech to give it a look ;the circuits on those things are not easy cake,will keep you updated cheers!

 

[rarebitusa]

Yep I did not many changes it might be something related to caps or diods or the voltage on the plates I will contact another Mesa tech to give it a look ;the circuits on those things are not easy cake,will keep you updated cheers!

Ok, it certainly seems you've tried everything. The only other thing I can think of is to take the FX Send and run it into something you can monitor with and see if the preamp by itself sounds any different. Good luck.

 

[Slash_83]

Have you tried another speaker? With another cable

 

[user 85366]

Hi Slash-83,yes I did with both.

 

[Nandrewjackson]

I don't have a specific idea of what it is, but I would guess internal switching issues. That ch2 doesn't seem 100% right. The ch3 is very wrong.
Maybe a bad preamp tube. Look at owners manual tube task chart for a tube that is only shared by ch2+ch3.

 

[MarkV User]

I wonder if it changes when the amp is warm or cold or gets a little bump. It could be anything that attenuates the preamp signal. If the signal were split between channels 2 and 3 it might do it. Sometimes the camera shows things that are true but not visible to the eye. Check in a dark room to make sure channel 2 is not lit up a little in ch 3 mode? Good luck!