Amp Experts Please Help!!!!

[Txhighroller88]

I have had horrible luck with my Mark V. I have had it in the shop 3 times now and only just purchased the amp a year ago and it hasnt even seen a gig!!!

Previous Issues: Fan makes clicking noise in Standby (still happens after being in shop 3 times). Channel 1 died (was a pre-amp tube). Lost gain in channel 3 (power amp tube). All tubes replaced amp worked for a week after previous shop visit. Then current issue occured.

Current Issue: I just got all the tubes replaced including Power and PreAmp. Channel 3 litterally has no bass. The treble is way too high. Even when rolling the prescense out treble is unbareable. It also has lost gain. Still has some gain but sounds very thin. This happened before and after preamp replacement. Anyone know what could be causing this?

Im going to be calling Mesa today. I have had more problems with this amp than I did my cheap fender deville. I seriously think I have a badly built MarkV.

 

[jdgebha]

Tubes aren't a sign of poor build quality. The fan is another issue. I would clean slate ALL the tubes with good ones from either Mesa or Eurotubes.
What mode are you using for chan 3? or does it affect all the modes?

 

[Monstercastle]

Did you buy it new or used? Are you using Mesa tubes or other? I agree with getting a full set of new tubes and see where it's at. Do you run things in the loop? Tell us a bit more about your rig overall.

 

[bandit2013]

What power settings are you using for each channel, and are you using full power or variac power ?
Type of power tubes (6L6GC or EL34) ?
What preamp tubes are currently in the amp?

When the amp is on and out of standby, how do the power tubes appear to look? At 90W power setting, to all power tube have a blue hue somewhere on the inside wall of the glass? (note: if EL34 type, they will not have the blue hue if any at all but you can see it surrounding the cathode if you look though the gaps in the plates.) You may also want to confirm the bias switch is set in the proper position for the tubes in use.

Also check the send level on the FXloop if you are using the FXloop in active mode.
For CH3, does the pentode or triode switch make a difference?

Is the load (speaker) plugged into the proper output jack? If this is a head, make sure the speaker cable is not a guitar cable.

Also verify if the reverb tank is plugged in properly. White wire should be in the jack closest to the rear of the amp.

I would also try disconnecting the footswitch cable and use the rotary channel selector on the back panel. If there is an issue with the logic controller in the Mark V, things may not work as they should.

I would hate to jump to conclusions, but I did a search on your other posts.... sorry to hear you are having issues with the Mark V. When you had it in for service, what was done to it? I would ask your tech to review the service records and indicate to you any changes or repairs to the internal circuit boards on the amp. Since you recently had some power tube issues, and if it is recurring, I may suspect there is an issue internal, screen resistors in the Mark V (depending on year???) have been problematic with some people. I lost mine about 2 or 3 years ago and replaced them with metal film high watt flame proof resistors of same value as the carbon comp did not hold up with one splitting down the middle this is usually accompanied with lots of smoke and nasty phenolic burning smell. (it smells nasty ) . Tube amp usually will not work after loss on the screen resistor or will sound really bad.

 

[Nicklotsaguitars]

The fan makes a clicking noise? It's obviously hitting something.
I recently had my 5 in a headshell. The footswitch relays made a clicking noise. If the amp was set to channel 2 or 3. That was down to the seemingly pointless screw that comes out of the chassis. It completes a faraday cage by contacting a metal film on the underside of the top of the original Mesa housing. My headshell is a homemade job.
Could your problem be similar?

Power valves don't affect gain. Particularly in Mesa amps. The 6L6's are biased so cold you'd never get em to clip. They ain't affecting channel 3's gain levels.