Hey, it is very likly not the boards, but a tube or a fuse. Turn the amp sideways, and look underneath the tube/light that is out. There is a fuse holder under each output (large)tube. Change the fuse. If you don't have a extra, go to radioshack and get the same size. They are about $2 per pack of 4. Power it back up. If it works, your done! If it doesn't, it's a good chance its a bad tube. If it works for awhile then goes out again...a tube going bad.
I had the same issue with my vk60. for me it was just a fuse.
I had the same issue with my vk60. for me it was just a fuse.