Fan noise can be heard on all channel

[masterMarkV]

Hi everyone ! New Mark V user here, got a good deal for a used Mark V Head (1400$ with Amp Gizmo included) but found a small issue...

I can hear the fan running on all channel. It seem to be more present on clean channel just probably because this channel is less noisy at all. If I turn up the Master or Output, the fan noise stay at the same level (is not beeing amplified). If I turn off the fan, channel become quiet and no noise at all but owner manual say to let the fan running if possible !

This is my first Mesa Boogie and of course my first Mark amp so I don't know if this is normal ?! I didn't find a GC with a Mark V head to compare noise.

As I see in layout, the Fan is located near the V7 tube (phase inverter), may be this tube is microphonic... ? If I knock the amp gently, the fan noise disapear shortly.

 

[Demon Of The Fall]

Hi, does V7 have the metal screen in place? all pre tubes has their corresponding metal screen in place?... https://www.youtube.com/watch?v=hPw_lJhWuZg#t=190

At very low volume (at my apartment after 10pm on a monday with my son sleeping next room) I can hear the fan but not through the amp... at normal volume (channel master at 9 o'clock and global master at 11 or 12 o'clock) I can't hear it at all. I hope it just a problem of insulating the tubes.

Greetings!
DZ

 

[masterMarkV]

Thank for reply !

All metal screen are in place, well seated. I will try to replace V7 to see if problem persist... If this is a microphonic issue, I will be able to isolate the preamp tube by tapping each with a pen !

The fan noise through the amp appear after 10-15 mins playing, so probably an overheat or microphonic issue ?! Or may be an electric noise from the fan, but this will be amplified with Master or Output setting...