Ok, so I did some testing on the tube. All electrical connections appear to be working as expected. I used a couple of alligator clips to apply power from he power source to the tube without the pigtail connected. Viola! Everything worked properly. Gain was high and the adjustable gain functioned normally. I reassembled the unit and tested again holding the device shut. Again, everything was bright and working as it should. I put the four screws back in and tested it again, and Boom, back to square 1. Low gain, adjustable gain not working. I removed the screws and sure enough, the unit started working normally again. I found that depending on how tight the cover was affected how the unit worked. At this point I have no idea why. I do feel however, that this latest discovery eliminates the tube as being defective. The tube appears to perform normally under the right circumstances. I now need to find what is causing the variance when the unit is tightly sealed (screwed together) vs. being loosely held together.