Mark V issues : Crackle popping ; changed V1 V7 but no luck

hello folks,

Need some help with identifying the cause of this issue I have been facing recently with my Mark V.

Issue : Crackle, Popping Hiss sound on all channels after putting it to ON (after being in standby for a couple of mins). Changes with volume - less volume - less hiss / cackle / pop ; more volume - more hiss / crackle / pop. As per the threads I have read here n on other message boards, it sounds like an issue with V1 or V7 (PI). Most likely V1. Amp warms (?) up a bit and the disturbing noises go down..

I tried : Changing V1 first. no change same issue. Changed V7 as well. nope, Didnt fix it. :evil:

Stange behaviour ?? -- All this Crackle, pop & hiss sounds is completely gone after the amp has been ON for a while(15 mins or so after its turned on).. all the disturbance reduces and its all clear after some time.. This is completely baffling to me . has any0ne noticed this ?

Any / All advise would be appreciated.

Thanks !

I'd lean more towards power tubes, since the problem is with all channels.

Monstercastle said:

I'd lean more towards power tubes, since the problem is with all channels.

Click to expand...

+1
Output tubes can definitely cause this problem.

One other thing (though, I admit, a 15 min warm up should not affect this)...have you tried bypassing the FX loop? The switching jacks used on these can cause noise as well.

I third the power tube suggestion. That's how my V sounds when the tubes are worn. Seems to me it happens if I don't let the tubes warm up enough before powering on.

Thanks everyone. I would have never thought Power tubes would be the issue.. hmm.. but then again, I am a tube amp noob, so....

Old BF Shred said:

Monstercastle said:

I'd lean more towards power tubes, since the problem is with all channels.

Click to expand...

+1
Output tubes can definitely cause this problem.

One other thing (though, I admit, a 15 min warm up should not affect this)...have you tried bypassing the FX loop? The switching jacks used on these can cause noise as well.

Click to expand...

Could you please explain how to bypass the FX loop ? I am not sure I understand this fully...


Thanks..

Small toggle switch on back panel next to FX loop jacks.
See page 40 of owners manual.
Also plugging a cable in from send to return jacks essentially accomplishes the same thing for this procedure. :wink:

Old BF Shred said:

Small toggle switch on back panel next to FX loop jacks.
See page 40 of owners manual.
Also plugging a cable in from send to return jacks essentially accomplishes the same thing for this procedure. :wink:

Click to expand...

Thanks Shred. Unfortunately, didn't help any... Been busy for a while and couldn't post. Fired it up last night and got the same thing again, this time I took and pencil and tapped on almost all the pre-amp & power-amp tubes; no luck.. Didn't get any microphonics,ringing, etc. 5minutes later the noise died slowly and I was able to play without any disturbances.. This thing is driving me nuts!!

Old BF Shred said:

Small toggle switch on back panel next to FX loop jacks.
See page 40 of owners manual.
Also plugging a cable in from send to return jacks essentially accomplishes the same thing for this procedure. :wink:

Click to expand...

Hard bypass completely eliminates the FX Loop circuit, including two triodes (V4A & V6B).

Using a cable between send & return simply bypasses the switching contacts in the FX loop jacks, but the entire FX circuit is still active.

Definitely not the same.

Dom

domct203 said:

Old BF Shred said:

Small toggle switch on back panel next to FX loop jacks.
See page 40 of owners manual.
Also plugging a cable in from send to return jacks essentially accomplishes the same thing for this procedure. :wink:

Click to expand...

Hard bypass completely eliminates the FX Loop circuit, including two triodes (V4A & V6B).

Using a cable between send & return simply bypasses the switching contacts in the FX loop jacks, but the entire FX circuit is still active.

Definitely not the same.

Dom

Click to expand...

Correct; not the same circuit or scenario.
But....to determine if the switching tab of the loop jack (usually return) has developed corrosion (which can definitely cause noise), either way should remove them from the circuit, although the switch also takes out the rest of the loop circuit (assuming the Mk5 loop is similar to other Mesa loops....granted, I do not have access to a Mk5 schematic to verify this).

I was trying to explain, simply, one easy troubleshooting step that Bankim could use to check this.
If nothing else, it is more info to provide a service tech (which if output tubes don't do it, would seem to be the next step).
Good luck to Bankim on this!

Take care! 8)