As it turns out, the PC board that controls HF is fine. There is 115 volts coming into the inputs of the HF system. Then, per schematic, it goes through a big resistor and feeds a high voltage transformer.
What I know is that 110v comes into the HF system, but nothing happens in the HF circuit after the transformer.
However, one more observation is that out of maybe 50 times I turned on the HF system, about two times there was arcing between output wires from the high voltage transformer, coming into chokes, and something near that area (it was a little hard to see). But during all other tries, there was no visible arcing.
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