chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/
http://www.r-type.org/pdfs/6j11.pdf
Is your pinout. The filament is 6.3 V, AC or DC, at 0.8 amps. This is a dual-pentode as you already stated.
With some finagling, and the data on the sheet, it would seem feasible to test each pentode separately, meaning you would need to connect only seven pins (5 + heater) at a time.
As it happens Compactrons are remarkably resilient tubes, and short of physical damage and/or an open filament, it should be OK. Question: Does it light up?
Peter Wieck
Melrose Park, PA