Yea I think I know where that is on this, its a small pcb by itself soldered into a connector, it does have a diode on it. Now the game is stuck on 31k mode, 15k boards will no longer cause the monitor to power on. I will try swapping out the sensing circuit to see if that does work.
Also, cbartek just informed me he plugged in a Wei-ya 29in chassis on one of these tubes today and it actually works with some minor imperfections on geometry. I have never heard of a replacement chassis from wei-ya, i've always assumed you needed the rodotron 666b. This might be my ultimate solution, just waiting to see a pic of his result first.