[morzh]

Anyways.
It worked. I mean, the 0603 resistor idea.
I think it is a simple and easy fix, works as expected.

Photos:

The 0603 1M thick film resistor with soldered 28 gauge wire leads.
   

Same compared to 1M 1W through-hole, app. size of that in the tube socket.
   

Inserted in the socket.
   


After this the tube works, the sector tracks the signal.
I suspect the 6U5 would work better, as it is the exact equivalent of the 6T5. But I am OK with 6E5. I expect it will work even better once I replace some tubes that I suspect may be somewhat lazy by now.