[37silverstreak]

Roy, The adjustable capacitors in the IF cans are called "Trimmers" and they are used to adjust the for the 455KC intermediate frequency. this is part of the aligning procedure, which is done to get the best performance out of the set. If you look at a lot of schematics they have a section to tell you how to go about aligning a set. There will be tables telling you how to connect a signal generator to the set and what frequencies to use and what trimmer caps to adjust for each section. In the case of the IF trimmers you usually connect the signal lead to the grid of the RF tube and set the generator to the sets IF frequency which is in many cases 455KC but older sets may use a different one. With the set turned on you will get a tone at the speaker. you would then adjust the trimmer caps in the IF cans to get a maximum volume at the speaker. you can do the same thing just by tuning the radio to a station and then adjusting the caps until you get the loudest signal. It's a little involved but not too difficult. If you want to learn more, there is a DVD made by Bret Menassa of Bret's Old Radios that walks you through aligning old radio's. I bought a copy of it from him on Ebay and I think he does a good job of explaining it.
Kevin