Over the years I have seen this problem a few times and thought that it would be worth mentioning.
The symptom is that there is no high voltage on the 11-065 ion gun control HV1 board, or the voltage is low.
On the system, the symptom will be no or low target current.
If you have this problem the first thing to check is whether or not C5 on the HV1 board is blown out. It is an electrolytic capacitor and these days most electrolytic have some creases in them which allow the capacitor to expand and release gas and fluid when it fails.
The location of C5 on the HV1 board is shown below.
For a recent 11-065 repair the symptoms were no high voltage on the beam and the COND was low. C5 on the HV1 board was obviously blown out so I replaced it. However I still did not have any high voltage on the beam, and the COND voltage was also low.
The resistors, capacitors, diodes and transorbs on the HV1 board all checked out fine. It was then that I remembered I have seen this problem once or twice before. What happened is that when the C5 capacitor failed some of the electrolytic capacitor fluid seeped onto the board. It was not really noticeable, but there was enough electrolytic capacitor fluid on the board to effectively add a high resistance to the board surface and load down the high voltage supplies.
The schematic for C5 in the filament circuit is shown below.
The solution was to clean the board with a diluted mixture of Alconox detergent and a tooth brush then rinse the board thoroughly in warm water. Avoid wetting the transformers. Blow the HV1 board dry with compressed air and then use a heat gun on low to completely dry the board.
After cleaning all of the electrolytic fluid off and drying the board everything worked fine.
Keep this in mind with any electrolytic capacitor failure where the capacitor blows out and leaks on the board.
If you need to check the drive transistors on the heat sink, they are shown below.