The A15MK clean channel has a low power

I bought in 2007 the MADAMP A15Mk2 rev 1.0 and it remained in my room until now that I had time to build
(more precisely I bought the A15MK1 de luxe ... but the instructions that I followed were of the MK2 1.0)

I'm testing the ampli with a 4 ohm speaker of medium quality before using my new Celestium
I noticed that There is a big difference in volume between the two channels

• channel 1 is very low
• channel 2 has the power reserve that we can imagine for a tube 15w amplifier

I twice inspected the wiring of the ampli and there should not be errors(I will do again in both direction from final ti input and viceversa)

can you suggest me where to mod the ampli in order to have a right clean volume?
or at least where to inspect more deeply to find possible defected components or wiring?

the retroaction goes from the 8 Ohm secondary to the E point on the schema
further info could follow on request

help please

thanks
Renato

hi
the schema that I used were of mk1 and mk2
Plans A15Mk1 Rev14a.pdf

unfortunately the development was done after 10 years of receiving
and the second schema was acquired in 2011 after losing the first (then recovered from a backup)

Plans A15Mk1 Rev14a.pdfPlans A15Mk2 Rev10D.pdf

the black shielded wire is the retroaction from the two F points of the MK2 schema
that is not seen in the picture but is attached to the 8 ohm output jack

I think I have to recheck everything but wich of the two schema? that I possibly have confused

regards