Channel 2 sounds weak and thinnish

[evilsaint]

Hi guys, channel 2 of my mark 5 has lost most of its volume. I get this weak, thinnish sound from channel 2 while Channels 1 and 3 sound great as they should.

I tried changing the preamp/poweramp tubes and cleaning tube socket, but no luck.
What other potential problems there might be ?

 

[screamingdaisy]

Is the FX loop set to come on automatically with channel 2?

 

[evilsaint]

FX loop setting is fine.

 

[OryCheyne]

Assuming it's the same when switching channels from the footswitch or rear channel selector?
Guess you would have tried all combinations and settings in ch2.
Could be a high resistance at any point along the circuit from dust or oxide. If you haven't already tried cycling all the pots and switches for that channel do so.
Question, are the reverb preamp valves individual for each channel? 12am here and I should be asleep, not looking for the manual this time of night.
Otherwise, strange but it might be a component, unlikely.

Good luck.

 

[screamingdaisy]

Reverb driver is common to all.

The V2 preamp tube is only in use by channel 2.

 

[evilsaint]

Yea. Tried all the combinations and cycling
between pots and switches of channel 2, but still no luck.

Could there be any internal fuse brown ?

 

[screamingdaisy]

Not that I've seen.

I'd give Mesa a call on Monday. Once you've checked all the tubes, fuses, cables and settings you're hitting the limits of user serviceability.

 

[evilsaint]

Too bad that I am a non-US user and my local Mesa distributor only knows how to rip us off.

 

[screamingdaisy]

In that case I'd try PMing Authorized Boogie.

 

[evilsaint]

Took out the chassis and had a inspection. Nothing was burnt inside.
Cleaned the jacks and the pots of channel 2.
Had test run and my channel 2 is finally back to normal.

But everytime when I engaged FX loop with nothing in the loop,
FX loop would cut-off overall volume of my Mark V dramatically and intermittently no matter which channel.

As long as I put a patch cable in the loop, there would not be any issue.
I never had this kinda FX loop problem and never need a patch cable before.

I am not sure the problem coming from "send" level pot or FX send and return jacks.