Cheers bud - you've saved me a shedload of time :-)

Turned out to be the 33uF 50V cap above R15. Got the trusty old meter out
and found this one to be 2.7uF - replaced with a temporary 47uF 50V cap and
the display was as good as new.

Just placed an order for 5 of these with RS so I'll pop over and pick them
up - hopefully I'll get a few more years out of my workshop amp (hooray -
music again :-)

Thanks again bud

Dom