[MrFixr55]

Hi Kettlechip and welcom to the Phorum.

The back panel question is interesting. I have quite a few radios that use power transformers, built around 1930 through 1949, which have no backs, as opposed to the transformerless AA5 style sets which almost always have backs and, in the case of newer postwar sets, have interlocks due to "hot chassis" design. The only transformer powered radio in my collection that does have a back panel (Other than my Radiolas which have a flip top lid and no interlock) is my RCA 1R91 "Livingston"

As to adding Bluetooth, one way around this is to add an "Aux" or "Phono" jack. This was often added by radio shops and the Zenith service docs in the mid 1930s had diagrams for the modifications. Generally the mod involves adding a SPDT switch, breaking the circuit at the input to the volume control (one "leg" of the resistor), connecting the volume control to the common or wiper of the switch. Connect the wire removed from the volume control to one "leg" of the switch. Connect the other "leg" to a jack for adding the audio source. According to the schematic, your radio should have an "aux in" jack already. It should be labeled Phone or TV, and the jack should be on the back panel. It may be that little pin jack on the rear right of the chassis but is unlabeled. On both the Philco Phorum Library and Nostalgia Air diagrams, the Jack is labeled J200 and the push button is PB10. What is interesting is that J200 is not switched. Apparently PB10 is designed to switch the audio output of the radio either to the volume control or to ground without switching the "aux / phono" jack. This is strange because a ceramic or crystal cartridge may load down the audio, affect frequency response or be driven by the signal.