[Yamamaya42]

The stupid focus potentiometer fried again, and smoked the new 560 ohm resistor that was feeding it, both being rated at 500v 5w, this happened as soon as it was mounted back to the chassis and it's ground, it had been working fine all this time out in the open, not sure why it did this, the 560 ohm resistor is hooked to the main filter choke through the H & V centering pots, (30 ohms), seems that the entire LV bias is fed through the centering pots, sort of like the early RCA sets, then the focus coil (409 ohms) / focus potentiometer & resistor then to the voltage divider network.

The only difference I see from this set and early RCAs is that RCA had the focus circuit in series with the -100v line, and this has it in series with the +250v line, other than that, they seem the same.

Since I can't get an original OEM pot, I guess I will have to keep the focus pot isolated from the chassis, and mount is elsewhere, not sure why it burned through the dielectric of the pot again, it's not like it is being hit by huge voltages or something. :/