[dconant]

Hello, I want to add a Bluetooth jack to my Philco 89. I'm thinking I can just add a stereo jack to the chassis sans switch and tune to a quiet spot on the dial. I would use two 1K resistors to tie the right and left channels together. I'm thinking I also want a cap to isolate any possible DC from the jack. Not sure where in the radio to make the connection. Can someone help?

Thank you,
Dan

   

[RodB]

Hi Dan,

Usually it's at the high side of the volume control where 21, 24, 25 and 26 meet. Be sure to feed the audio through a cap, maybe 0.05 mfd. Let us know how it works. My 650 didn’t work that well. The radio signal interfered. If I want to get it to work right I'll have to figure out how to shut down the radio when the aux audio is used.

[MrFixr55]

Edited 10/22/2026. You can do this with a DPDT switch. Connect one half of the switch as Rod described. The "common" of that half of the switch goes to the leg of the volume control where you broke the connection between the control and the radio's audio signal. The other leg of that switch connects to the "aux" input. You can use one or 2 RCA jacks or a 3.5 mm phone jack. If inputting a stereo signal, "merge" the signal using two 100 Ohm resistors joined. The "legs" of these resistors go to the 2 jacks. The "junction" goes to the "Aux in" terminal of the switch through the 0.05 uF cap that RodB recommends. I actually did this on an 89 years ago and it sounded great, much greater than the radio itself. It really rocked!!! The owner was not interested in the SW channel so I rigged it so when he turned the bandswitch, it hit the actuator of a SPDT microswitch. I did not have a crosstalk issue.

I made the above mod out of despiration before the 3rd attempt to rewind the oscillator coil and update to a 77 tube finally made the set work. It was interesting that the set used the 75 Detector / AVC / 1st Audio tube but not the 2A7 pentagrid convertor. The competing RCA R28 used the 2A7, used an RF amp, did not have an IF amp and used a biased detector, making the Philco actually the better set, the crappy autodyne convertor notwithstanding.

The other circuit of the DPDT switch is used to ground out the circuit not used. The "common" of that leg of the switch is grounded. Each leg of the switch goes to the opposite (not near) leg of the other circuit. In other words, if the top right contact is the Aux signal, run a jumper from that terminal to the bottom left contact of the switch. If the bottom right of the switch is the radio signal, run a jumper from that terminal to the top left of the switch. The middle left is ground. the middle right connects to the volume control. when the switch is in the "Aux" position, the radio signal should be grounded. When the switch is in the "Radio" position, the Aux input is grounded. This will solve the crosstalk issue.

[dconant]

Ok I did the hookup without the switch just to see what I would get. My best results was disconnecting the antenna and tuning to a quite spot on the lower end of the AM band. There is more noise on the upper band even without the antenna. I did not detect any hum or noise. The only thing I pick up is the neighbor's electric fence. Must have a wire touching the grass. Sounded pretty good to me. So I guess I'll go with that.

Thanks guys.
Dan

[radiorich]

Hello Dan,
Most likely one of the new switching power supplies for your neighbor’s electric fence. Even the FM band is starting to experience interference from all this new wireless technology.
Sincerely Richard