SP 14 Uneven Gain

I build this SP 14 about 5 years ago and it has been a great performer.

Recently I've had to adjust the right gain all the way up and reduce the left gain to about 75%.

I don't know if my tubes are getting weak or if there is another problem.

May I request your input as to what you think may be the problem?

The original tubes were used when I got them.

Thanks,

John

Swap the tubes Left to Right and visa-versa....See what happens. Is there any noise in the volume controls. If yes, spray contact cleaner might fix the problem.

I'll try to swap them out and see if the situation reverses itself.

The volume controls are quiet.

I switched the tubes with no change in volume.

I then re flowed the solder on the right and left gain.  It worked!!!

poor solder connections are the source of 90% of all problems we find with customer build tube gear.