[MrFixr55]

Hi James,

Congrats on getting as far as you have. Line / battery powered portables (Sometimes called AC-DC / Battery or 3-way powered portable radios) are one of the more complicated radios to work on due to the complexity of the power supply circuit.

Re the hole that you describe. Is it a full hole or a notch where the case joins the back cover?  If the latter, this is where the cord routes outside the case when the radio is run off house power.  If it is a hole, it may be to pass an external antenna wire into the radio.  There is a green wire with a u shaped lug that is grounded to the chassis.  Remove this connection from ground and you can connect a long wire antenna to this green wire.

This is a very sensitive radio because, unlike the typical 5 tube radio (Convertor, IF, Det / 1st AF, Output, PS Rectifier), this set has a tuned RF amplifier, like very sensitive console radios. In addition, these radios are the children or grandchildren of "farm radios" which by the rural nature of farms, had to be more sensitive than radios used in urban or suburban areas.

Are you able to receive any station over the static?  Do you have another AM radio that does not use a "loopstick" antenna to compare reception to?  In the past 20 or so years, noise pollution from CFL and LED lights, computers, WiFi, remotely read electric meters, the "Internet of Things", etc., etc., etc., have made AM reception almost impossible inside the house.  I live in a suburb of NYC with at least 20 AM stations that give a strong signal (At least 5 of these being 50KW "clear channel" stations), and I can receive only 2 of these inside my wood frame one floor single family home that has aluminum siding on only one side.  I must shut down every flat screen TV, computer, light, etc. in order to receive anything, even with a long wire antenna, unless the radio has a ferrite loopstick antenna. 

The following steps are if you still have intermittent power to the radio:

If you have not done so, press that tab that operates S100, the Line / Battery switch up and down several times.  Re the power switch, take a good look at it.  There should be 4 contact lugs on the power switch, 3 contact lugs on the volume control.  There is a shield over the power switch connections to prevent electric shock, as there is no interlock for the rear cover.  This shield covers the 4 power switch lugs.  A pic from the similar 46-350 is attached below:
   

To clean this switch or check its continuity, you need to loosen the hex nut, slide the switch from its bracket and pry off this cover.

This is a "DPST" (Double Pole Single Throw) switch.  One "pole" of the switch switches the A-, B- and Line Power return.  The other pole switches B+.  A and B batteries are both switched so as to prevent discharge of the batteries through capacitors.  Note that for Line Power (AC or DC House Current), the "neutral" is switched.  This is one reason why you cannot use a polarized cord on these portables, as they cannot be rewired to only switch the "Hot".  The other reason is for those radios, which, like yours, require the user to plug the power plug into a "socket" which operates the Line / Battery Switch (S100 on your set).

This is what is known as a "warm chassis" set. The "ground" (common A- and B- return) is isolated from the chassis, but to pass RF, a 150KOhm resistor and 0.05uF capacitor couple the RF signal to chassis ground while limiting line current. Whether the chassis is at "ground" potential depends on the polarity of the power cord and whether the power switch is on. For example, if the switched leg (the A-, B- "ground) is connected to neutral based on how the plug is inserted into an outlet, the chassis will be at ground potential with the power switch on, but with the switch off, the chassis becomes "warm" (connected to the hot lag through the cap, resistor and the cold 117Z3 filament.

Refer to the schematic and trace the wiring as best that you can.  The AC/DC Line Power - Battery Switch is drawn in the AC/DC House Power position.