Late to the party (as I'm usually not around here on weekends). But a few things:
- The resistor smoking on the AR is due to a bad connection between the AR and game board, most likely at the edge connector. This is common on these games. Clean your edge connector with a fiberglass pen and DeOxit. This isn't optional, it's a must do for any Atari game, to prevent future power problems. Also apply DeOxit to all Molex connectors in the cabinet, especially the ones on the AR. Here's what you need:
https://www.ebay.com/itm/201067762269 (Fiberglass brush)
https://www.ebay.com/itm/306144854777 (DeOxit)
- Loss of half of the screen, with no blown fuses, means there's a cracked or bad connection to whichever one of the frame transistors controls that axis and half. This can happen at the header joints, header traces, or a break in the wiring to/from the frame transistor, and also a loose transistor socket. It looks like you found it, but FYI, you want to actually find these issues, not just guess. That way you know you really found and fixed the problem, as a lot of problems (especially intermittent ones) can come and go simply from handling the board. Also, the transistors you replaced on the deflection board are still fine, I hope you saved them, as they're like $5 each these days. You can always use them as spares.
- The HV diode had nothing to do with your issue here. When the HV diode has problems, you get blooming (or just no picture), not brightness problems. You disassembled the diode, but be aware that all that crap inside the boots needs to be cleaned out. I also solder the springs (springs, not the wires) to the diode, then put the diode back in the boots. It's critical to do this correctly, otherwise the diode and boots will burn up again.
The way to test this is to run the monitor for ten minutes, power down, discharge the CRT, then feel the diode with the back of your finger. It should be cool to the touch. If it isn't, that usually means one or both of the connections to the diode is not solid, and has enough resistance to generate heat. (Or it can mean the diode is bad in some cases, but that's not usually the case.)
Note that I have a longer post about doing the diode cleaning here:
I have updated first post with some of the myths and their status. Will try to catch up and add some others but if you feel real strong about changing status of one, quote it and post a fact. The fun ones are fine but too many for me to try and update.
forums.arcade-museum.com