Lights and sound cut in and out today for 5 seconds while playing.

[Ascendance]

I was fiddling around expermenting with tones today for a bit. I have not had time to play in a bit cause of college.

Anyways I watched all the lights go dim for about 4-5 seconds on my amp and the sound cut out on my mark 5 90w. I struck a few more cords after the lights stoped being dim then shut it off out of fear I might damage something?

The footswitch lights went dim as well during that 5 seconds.

Im still rather new to tube amps. I got my mark 5 35 in 2020 im just a hobbyist guitar player anymore. It was good but recently snagged a used mark five 90w in excellent condition on reverb.

Is this signs of a failing power tube? If so how do i figure out what one is the bad one.

If its something else please let me know.

I bought all new preamp tubes a while back but have not had time to put them in as well. So if its a preamp tube issue I have replacements.

 

[rarebitusa]

Just one suggestion... 1st check the fuse. Then pull the Rect tube and set all of the chans power to 90W, chan gains/masters and global master to 0 and see if it powers back up in Standby. If it's stable, while still in Standby manipulate all of the footswitch selections and see if they switch state as expected, no chattering or funny noises. If that's ok. Go off Standby and check for redplating power tubes, then slowly bring up each chan to low volumes and test.

If you get this far you're making progress

 

[Ascendance]

Just one suggestion... 1st check the fuse. Then pull the Rect tube and set all of the chans power to 90W, chan gains/masters and global master to 0 and see if it powers back up in Standby. If it's stable, while still in Standby manipulate all of the footswitch selections and see if they switch state as expected, no chattering or funny noises. If that's ok. Go off Standby and check for redplating power tubes, then slowly bring up each chan to low volumes and test.

If you get this far you're making progress

Ok thanks ill try this as soon as I can. I just hope its not the diode issue.... or something worse...