Help with Lead Master volume problem

[droogie]

On my Mark IIB I'm finding that the lead master functions up to around 1, no effect at higher numbers. Master 1 works normally and brings the overall volume up as you'd expect. Do I have a preamp tube issue? Do I have a human error issue? Any help would be greatly appreciated.

 

[MrMarkIII]

This is from the Mark III manual, but it applies to most any master volume amp, so:

"MASTER: This control regulates the overall amplifier loudness and it remains functional in all modes. If it is set extremely low, it will
seem to reduce the loudness available from the Lead Mode.

LEAD MASTER: This control regulates the loudness and is active in the Lead Mode only. Because it works at the same time as the
regular Master, whichever one is set lower will determine the maximum Lead Mode loudness."

 

[droogie]

Thanks!