Valvestate 8040 too loud on boost channel

[SuperPunky]

Hello forum, this is my first post here.
I have an issue with a VS 8040. I bought it second hand and all the pots were completely wore out so I replaced them all. I measured them and they're all ok (VR1= A100K, VR2=A1M, VR3=B22K, VR4=B220K, VR5=A1M, VR6=B22K, VR7=A1M, VR8=B220K, VR9=B100K, VR10=B22K), the solderings are OK as well.
Now the controls on the normal channel section work fine but the volume on the boost section is really too loud. It sounds fine with volume at 0.5 or 1 (gain, contour, bass and treble are fine) and becomes too loud after volume 2. At volume 3 it starts to hiss with positive feedback. I suspect that there's a shorted cap somewhere because the solderings seem to be ok.
I'm lost because there are no test points on the schematic. Where can I try to focus to find out what's wrong in the boost section?

PS: I don't think that's related, but this amp makes a pop when turning on and off

 

[Gbc66]

I have this very same problem. I replaced most of the pots due to wear and noticed vr9 (boost ch volume pot) is 100k linear. I always thought volume pots were log pots? Marshall schematic confirms its linear but its behaving like it should be a log pot.
Maybe its the way the circuit is designed as the schematic listed log pots are bass, gain and contour.
Any help on this would be appreciated.

 

[Jon Snell]

I have always fitted Log pots in this chassis and all of my clients said how much more control there was, after doing that.

 

[Gbc66]

Did you fit the same value just log?

 

[Gbc66]

Log 100k ordered. I'll report back later.

 

[Jon Snell]

Same value but Log.

 

[Gbc66]

100k log pot sorted it....although
When the volume is totally off you can still hear the guitar being played albeit very faint. I can live with that though.
Maybe because the circuit was designed for a linear pot? Who knows!