studiomaster focus 808 600w power mixer

[rjb100]

Hello all
This is my first post.
Could any one please help with a Studiomaster Powerhouse Focus 808 600w powered miixer fault.
I have found two 'roasted' resistors on board R1A1-4.
Before I replace them I was wondering if I should be looking to check any other components relevant to these resistors.
I don't have a circuit diagram so I'm working in the dark.

Thanks
rjb100