[drh4683]

Id be surprized if one of those diodes were bad, but it has happened. How is the blue left side convergence control? Lots of times those overheat and burn up. The blue shaft would be brown nearest the pot from overheating. I think those overheat though from leaky x6d diode. You'll probably have to pull each diode from the circuit to test. Lots of them have very low resistance shunted over them.
Be prepaired for loosing color from the left side of the screen. It happens on many 4 tube hybrids. Its a bad (high esr) 100uf@35v lytic from the 24VDC supply to the chroma duramodule under the chassis. You might want to check that one before going any further. Its usually a foreign made cheap cap, either gray or orange in color.