Well after a week of messing around I replaced Q690 (IRFPF50) with a
2SK1217 and got power back to the mainboard (power LED on, degauss then into power down mode but no CRT).
I found a blown resistor (r861 .33 1/2w) which supplies 210volts from the secondary side of the main xformer to q855 and the (I think) horizontal & vertical driver (pulse?) circiut, and also to q680 which somehow connects to the flyback EHT_+B and q690.
So now the new q690 is blown and I'm back to the clicking and no power!
Back to where I started.
The flyback seems to test as good after following instructions from people who replied here earlier (thanks for all your help).
Any ideas anyone?
Regards,
Kevin.