Granddrink
New member
I had a failure of my one year old Mesa Express 5:50 Plus head and had it repaired under warranty. It was a difficult problem to diagnose and it began to fail at a gig by distorting and losing power on the clean channel (Channel 1). I tried to troubleshoot it by replacing the power tubes and eventually all of the preamp tubes with no improvement. At some point the reverb quit too. After bringing it to a local Mesa authorized repair shop, the final story from the repair tech was that the reverb failed due to a switching transistor and the distortion was caused by a bad capacitor.