Quote: So after gathering dust on my bench for the last 5 months while there was a ban on melting lead in the house due to pregnancy, my 2nd daughter Ava has been born. I pulled out this frustrating project and had a go at it with renewed enthusiasm and it is now working fine and sounds great. To close the loop on my troubleshooting and resolution here is what I did. I followed the advise and painfully dis-assembled the heatsinks yet again to go over the bottom of the board with a fine tooth comb. I did find solder joint I was not happy with and for good measure reflowed a lot of the ground connections with a larger tip than the last time - this sped up heating the groundplane significantly! I re-did the LEDs with thinner wire and re-attached the heatsinks and still nothing. Cr*p! So I started probing again and found the problem - so simple! I did not have continuity between the switch wires regardless of the position of the power switch. Checking closer I determined I did not have a good connection between one of the fast on connectors and the wire connecting the switch to the board. So I removed the switch and jumpered the switch connection and the LEDs powered up, the tubes started to glow and the amp worked. Moral of the story - take small steps and eliminate the easy things before you just to conslusions. I could have saved myself a tonne of pain! Thanks to Tomb and the_equalizer for helping me out.