[Hallicrafters] What's the differnce?

[Brent Seres]

As a newbie to this fun, can someone tell me what the electrical 
differences are between the s40, s40A and s40B. I have downloaded the 
S40A manual from BAMA, and a quick glance seems to indicate that it is 
pretty much the same as the S40. My S40 howerver uses a #80 rectifier 
tube, and seems to be missing  a trimmer (C22) in the oscillator section.

Thanks again

Brent
VE3CUS