[Collins] kwm-2a problems

[YASH@aol.com]

Hi 
Need a helping hand. all of a sudden lost filament power to all tubes except the string consisting of v-7,17,5,13 9,10 and 8. I see they are all in the same stringthe remaining string are also fed from the same pin on the 516f2 supply, pin 8and 9 are tied together ,per my schematic.have voltage at both pins but no filament lite in the remaining tubes. I keep looking but nothing pops out. see no burnt resistors,caps etc. I guess I need a little steering in the right direction.Any help on this problem would be a great help
thanks
dale k8peo