Your Delco diagram is on the following site. You'll have to download per instructions and you'll need the special viewer, which they list there, too.
The way the site works is you click on the index and look first in the index for your set, then go back to the original page I list here and open the corresponding year volume. Your Delco is in 1959 on pages 18 and 19. Apparently it's a set for a Buick. Sometimes instead of a year the index will indicate a volume number. Count from the beginning of the yearly downloads to get the volume number. The first group of several years together is volume 1. Then starting with the individual years are volume 2, 3, etc.
http://makearadio.com/beitmans/index.php
Edit: By the way, I looked up your Silvertone 6220 and it's in the 1946 volume of the above site on page 120, and very clear, easy to read. Another By the Way note, of academic interest, perhaps, the 101 that starts the model number of this radio (on the rear chassis tag) means it was made by Colonial, which Sears had purchased at one point.