Buzzing From A 5e3 Bright Channel

[Gerard]

I just got done building a Mission 5e3 kit. This is my first dive into tube electroincs and I have learned alot. I must say that I am throughly pleased the the quality of the kit.I know I made the right choice by selecting Mission Amps. I spent 9 hours building the kit and the 15 hours trying to "fix" it.The problem I have is with the bright channel and tone.With a guitar pluged in the bright channel, the tone and volume work untill you get to #11 and then the sound cuts out and a buzzing noise is heard through the speaker. It only happens if the bright channel tone or volume is turned above #11. You could have the volume on #2 and as soon as you turn the tone to #11, the sound cuts out and a buzzing noise is heard. When a guitar is pluged into the normal channel it sounds and works great, but if you turn the bright channel volume up from 0 to any other number the buzzing and cutting out carries over to the normal channel. I have spent MANY hours tring to trace down the problem with no avail. I am not ready to send it to Mission Amps for a repair!. I just need some help.Thanks , Gerard.

[Chuck H]

I am not familiar with the 5e3 kits. But what you describe is a classic parasitic oscillation. I do think Bruce provides layouts and instruction for assembly. Any deviation from the layout can result in parasitics. Double check your layout and be sure none of the leads are out of place. Other than layout it could be a grounding issue. A cold solder joint or fogotton ground lead could also be the problem.

Chuck