Hi Warren

Long but good read, thanks for all the feedback, it will come in handy for sure.

When I replaced the 2 diodes that make up the new dual diode tube, thought about the snubber caps and resistors across them. I have heard they protect the diodes from surges and also help reduce ringing which probably also helps lessen IMD.

Turns out another Ham in Texas KD5WT tested his Tbolt and he does have a "hair" of needle movement on the mA meter for the plate in TUNE.
Perhaps not as high as mine, but I am gonna figure with the higher plate KV and the possible mod from AB2 to AB1 perhaps thats normal for the TUNE position.

Tried to resume testing today but the KV supply was being overloaded, and it threw the breakers in the panel. At least I know the breakers in that box work now. I was bummed that something else went out on me - however it was the safety interlock providing the dead short on the
HV line the way I guess Johnson intended it to be. Makes me wonder how often people did that back in the day, which for sure puts wear and tear on the Thunderbolts PS.

The HV supply, a Heathkit KS-1 has (2) round glass type 15A fuses on the outside of the chassis - they are the kind used in older houses AC line fuse boxes back in the day. When they blow you can see the broken metal line inside. These have been hard wired short at the base pin to the screw thread. Id like to put breakers in there, but I hear those kind are unreliable.

After defeating the interlock, I powered up just the filaments with the bias plug in and no HV just to make sure all is well, and its looking ok again. Tomorrow will apply the HV in standby and maybe get brave and apply an input RF signal.