[Eric]

I have a Zenith 7-S-240  http://www.nostalgiaair.org/pagesbymodel...025342.pdf 
 that is done and plays well, my problem is the eye tube it had a 6T5 which only the outer ring lights pretty weakly. I have changed R15 1 meg resistor the original was open. I have put in a 6U5 in place of the 6T5 which is impossible to get at a reasonable price if you can find one. The problem is I'm not seeing the sensitivity on the stronger stations. Is there a resistor that I can change the value to increase the sensitivity like R-14 22k

Thanks 
Eric