Lost all volume/tone in 10W/45W setting..Help?

[HeadlessAxeman]

Ok...so after a long time (2 months or so) of playing in 90W mode only - I switched down to the 10 W / 45 W mode last week and found a hiss/crackle sound in both wattage modes across all three channels. Whats more - I can barely hear the tone / volume.

When I switch back to the 90W mode - the amp clips beautifully! in all three channels and functions normally.

Something wrong? I am not sure if its busted tubes...coz 90 W mode works great...

Any inputs would be greatly appreciated!
thanks in advance!

 

[rocknroll9225]

id say its probably a busted output tube or the rectifier tube (depending on your channel/settings)

 

[SteveO]

Channel three is always diode rectified regardless of output setting, so that should help with the troubleshooting right there.

 

[HeadlessAxeman]

@SteveO

I'm not sure I understand mate....

Sorry for the delayed response -

 

[SteveO]

Channels one and two are tube rectified in 10 watts, diode rectified in 90 watts, and either/or in 45 watts. Channel three is always diode rectified, no tube rectifier at all in that channel. At least, I think that's how I remember it!

 

[domct203]

Sounds like a bad rectifier tube to me.

10W mode is always tube rectified, all 3 channels.

45W mode is selectable diode/tube in ch's 1 & 3, and always diode in ch 3.

90W mode is always diode rectified, all 3 channels.

Dom

 

[HeadlessAxeman]

got a call back from MB ...said its a blown 12AX7 rectifier tube issue *most probably*

going to have to go through the arduous task of trying to find out which one!
blah

Which brand of 12AX7 do the Mark V's ship with?

 

[domct203]

The only rectifier tube in the MKV is the 5U4GB. None of the 12AX7's are used as a rectifier, nor would they be.

Tube suppliers vary over the years. The current Mesa 12AX7 is a relabeled JJ supplied by Ruby.

My money is on the 5U4GB. Replace it with a new one. They are cheap. If it doesn't fix the issue, you will have a spare. You should always have spare tubes on hand for troubleshooting.

Dom