Happy Days, my amp lives !
Now appears the faulty 12ax7 was the culprit.

I found a Night Train schematic which displayed a 5w 12ohm between the EL84's consistant with Marcels, Simons & Docs input confirming amp is cathode biased.

I swapped all tubes with near new mesa boogies (which could be any manufacturers from researching) and Boom. Sound again!

Thanks all for the assistance.

regards
Guvna