[Radioroslyn]

>1.  What is that thing with the two concentric circles in the lower-left quadrant?

Looks like a motor, the diagram may be for a set w/a phono.

>2. Are these y-caps because they each go to a (common/chassis) ground?  Or are they x-caps because they bridge the mains (L-N)?

Neither didn't have X-Y caps in '35. Can you replace them w/ x-y caps sure.

>3.  Because the caps are upstream of the on-off switch, doesn't this mean that the chassis is always hot?  (I get the voltage divider and minimal current points, but why not move the switch upstream of the caps?  Or does this mean that you can get shocked if you touch the switch and a ground at the same time (if the wall plug is not spaded)?)

Would really consider this to be a HOT CHASSIS. Typically that refers the set that have one side of the ac line connected directly to the chassis. This set up can be dangerous if the hot side of the line is applied to the chassis.
In your Philco the line is connected to the chassis but thru two caps so what you end up w/ is some small leakage current @ low voltage. This leakage can be eliminated by connecting an earth ground to the chassis. I don't recommend using the ground connection from the house wiring as it can be a source of interference via modern electrical devices.

>4.  Finally (for now) if you ground the chassis to earth (cold water pipe, radiator, etc.) does this eliminate any possibility of a shock from the chassis (per 3 above)?

Yes if you consider the leakage a shock hazard.

>5.  Another "finally": If I want to put a fuse in the power circuit, where should it go?

I'd put it on the switch side of the power transformer.

>6. What size fuse should I use?

2 amp.

7. Not quite sure what diagram you are using as I couldn't find any that had a motor associated w/it. Would think it's a 16B code 121 (table radio) I'm pretty sure this http://www.nostalgiaair.org/Resources/139/M0013139.htm would be the suitable diagram for your set.


GL