MARK V struggling to come to back to life...

[HeadlessAxeman]

switched on the Mark V after almost a week...and I could hear no sound...channel 1, channel 2, channel 3 - all three wattage modes...continued to flip the switches in hopes of coaxing the Mark V back to life...no luck...

After about 2 minutes, the amp comes back to life..for a second or two..and then goes back dead silent again..making a lot of crackling noise in between.

I do know that I had one suspect pre amp tube that might have gone bad..have a replacement on hand, but since I mainly stay in 90W mode channel 3 all the time, figured it wasnt as urgent ...

Now I'm not sure if the pre amp tubes are blown or power amp...
Switched the fx bypass off to HARD BYPASS and the major hum came in through the speakers..no microphonic stuff ..just pure static.

Any ideas if it could be something more than the pre-amp tube ?(which Im going to try swapping out this weekend)

Thanks yall!

 

[screamingdaisy]

90% of the time I don't get any sound through my amp it's 'cause my guitar's volume was left at zero. The other 10% is stuff like the guitar not being plugged in or a patch cord between pedals being unplugged.

Assuming it's none of those it sounds like a preamp tube.

With bad power tubes I've always either gotten some sort of sound, obvious red plating or a blown fuse (or a mixture of any/all of those).

 

[yeti]

bad PI tube

 

[HeadlessAxeman]

Thanks guys..it turned out to be the tube.

 

[MusicManJP6]

Thanks guys..it turned out to be the tube.

Step #1 in troubleshooting a tube amp.... check the toobz! Glad she's back up and running.

 

[yeti]

which one?

 

[SteveO]

which one?

The bad one! :mrgreen:

 

[HeadlessAxeman]

It was the one two to the left of the v1/v2 that are arranged perpendicular to the back face..must be v4?

However - I'm not sure if indeed there was a loose connection somewhere..(although I checked for it)..because it didn't explain the loss of sound in the 90W channel 3 mode (solid state rectification?)

 

[mule#1]

Were any of the tubes glowing? I have a problem and only the 5U4 tube is glowing!

 

[Neptical]

Whenever I see/hear the word 'crackling' as an amp issue, I'll automatically inspect V1 tube first and foremost!