"Phil Allison"
"Gareth Magennis"

The problem is around the two Lateral Mosfets Q16 and Q21 (EXC10N20 /
10P20).

Another major problem is actually getting these Mosfets - you can't, as
far as I can tell, and Allen and Heath no longer supply parts,


** You did not look very hard ..

http://www.profusionplc.com/pro/gex/...teral%20mosfet

The " R " suffix is of no consequence for your amp, just an improved
version.


.... Phil