No sound from amp post Tube Overhaul

[HeadlessAxeman]

Hello boogie heads,

After having had my Mark V for nearly 3 years now, I decided to swap out all power amp and pre amp tubes with OEM 6L6's and 12AX7's and the rectifier tube (overhaul of all tubes)

After the swap, i hooked everything back up together (I have a Boss GT 10 sitting in the FX loop of the amp), I switched the amplifier on - gave the tubes time to warm up and tried testing it with a few chords...............I got a clean channel sound in all three amp channels ...

baffled...I tried a few more things before I switched to hard bypass and fx loop off....now all I heard was a wall of silence on all three channels.

flabbergasted, I pulled the GT 10 out of the loop altogether and the final chain was Guitar->Amp->Speaker cab....absolute silence again ...

I swapped the 5U4GB tube with the old one and still no sound in the straight simple signal chain...

I need some help/guidance from y'all - should I be looking swapping out V1 instead? I don't understand how I got only clean sounds on all three channels (with the GT 10 processor in the FX loop) with all the right gain settings. I've doubled checked my wiring and perhaps it's my lack of understanding of the pre-amp chain..unsure what the issue was?

I've called Mesa and left them a voice mail - hopefully will hear back in the next couple of days.
Meanwhlie - any inputs are highly appreciated...

Tnx \m/

 

[jb's 52]

Is the channel select in the back on channel 1?

 

[HeadlessAxeman]

turns out swapping V1 worked ..at least a little bit..

now I have microphonic noise in ALL three channels (microphonic noise is NOT present when I select the fx loop - but I get no gain/distortion /unable to push it to clipping in any of the channels)

The tap test has failed me so far..I can't make out a difference by tapping on the pre-amp tubes...

any ideas?

 

[bdubbs]

The only thing I can say is it sounds like the power section may be alright since you got sound through something that was in the effects return. Definitely something to do with a pre-amp tube. Maybe troubleshoot channel by channel. Find a schematic with what each channel uses and do that first? Its tough with the map because there are so many 12ax7s in the thing.

 

[K-Roll]

if you still have the old preamp tubes do the following -

put all the old preamp tubes in, if those sounded all right before the swap..

Then start swapping one old pre-tube for a new one .. only one at each time and try figuring out which is the problematic one.. sometimes you buy a batch of new tubes and realize that often more than one is problematic..

you may have multiple new pre-tubes going kamikaze..

 

[MichaelC4]

sometimes you buy a batch of new tubes and realize that often more than one is problematic..

you may have multiple new pre-tubes going kamikaze..

I bought 4 new Tung-Sol 12AX7s for my 50 Cal+ from Amplified Parts. 2 of them were bad. Amp wouldn't even make a sound.