[MrFixr55]

Hi Coffeeboy, 

First off, Welcome to the Philco Phorum.  Plenty of Phine Phriendly Pholks Phull of Philco Pfacts (see a pattern here?).

Secondly, don't worry about not figuring this out.  It is a simple radio complicated by a couple of things, not the least being that this is a transformerless set.

The Schematic is located in our library, but a link is here:
Part45-Philco 1940 RMS Year Book.pdf

Below is a section of the schematic that I marked up for installing an "Aux Input".  This can be an RCA Jack, a 3.5mm jack or you can wire your Bluetooth receiver output here directly, but a jack is preferable:

   

Below is a closeup view to show the detail better:

   

The switch is the easy part.  The red X (yes, poorly drawn.  My art with a pen and paper is bad enough, trying to draw with the eraser type pointing device is worse!) indicates where you break the connection.  There are 2 "ends" to the resistance element in a "pot" (potentiometer).  The side that you are breaking into has a wire (possibly blue) going to the IF output transformer secondary (This is the detector output), one end of a 3.3MegOhm resistor (the input to AVC) and a 250 pF cap (Detector RF Bypass Cap).  Once you break this connection, wire in a SPDT (single pole double throw) switch.  The common of the switch goes to the volume control.  the wires disconnected from the volume control go to one leg of the switch.  The other leg goes to the pin terminal of an RCA Jack or the tip terminal of a 3.5mm phone jack.

Now for the dicey part.  What to do with the other connection (the body of the RCA Jack or the phone jack).   

A 120V outlet in the USA has one pin at "Neutral" potential, and the other prong at "Hot" potential.  Neutral and ground are tied together at the Service Entrance equipment, making neutral potential and ground potential the same thing.  This means that one prong of a plug is at ground potential when plugged in, and the other prong is 120V above ground.  This set like almost all transformerless set is a "Warm Chassis" set.  The difference between a warm chassis and a hot chassis is that the power line connects to the chassis of a hot chassis set bit in a warm chassis set, the power connects to the chassis through a cap, for the purpose of conducting RF but not the AC.  Ordinarily, adding a polarized plug to ensure that the chassis remains at neutral potential, not hot potential will add a measure of safety.  The problem here is that almost all of these AA5 or AA6 AC-DC sets put the power switch in the B-, filament return, chassis side of the radio.  See the complete schematic from the link and the detailed area, shown below:

   

Because of this, if the plug is such that the power switch is at neutral potential and closed (on), the chassis at neutral potential, but when the switch is open (off), the low cold resistance of the tube heater string puts the chassis at hot potential.  If the plug polarity is such that the switch is in the hot leg of power, the exact opposite occurs, with the switch off, the chassis is at neutral potential through the filament string, but becomes hot when the switch is on.

This becomes a large problem when adding an aux jack.  If the return ("Body "of an RCA jack or "shield" if a phone jack) is connected to B- then the body of the MP3 Player, CD Player, etc. becomes hot.  If connected to the chassis, it becomes "warm" and hum may occur.  In the above diagram, I show the body of the RCA Jack going to "ground".  This is the safer way to do this but the safest way of doing so is to make the following modification.  Refer to the diagram below:
   

The blue line indicates the "B- and heater (filament) return" circuit.  The first part of the mod is to disconnect all connections from the power switch and connect these wires directly to each other.  The second step is to put the switch in the "Hot" side of power (the wire that goes to the pilot light and 53 Ohm resistor.  The third step is to add a polarized plug with the wider pin going to the Neutral and the narrower ping going to hot.  If the connections are made in this manner, then the return of the jack can be connected to B- instead of the chassis but care must still be taken, I would only do this if the jack is only to be used for the Bluetooth.

Finally, how to power the Bluetooth receiver.  the easiest and safest way to do so is to use batteries, or if the radio has room, a power supply having a transformer.  If using a high efficiency "brick", the output MUST be isolated from the power line.

Hope this all helps.