The PHILCO Phorum
40-180 phono plug - Printable Version

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40-180 phono plug - Patrick - 04-07-2020

I know this subject has been beaten to death, but I can't find specifics. Customer wants to add a phono plug to their 40-180. Ron posted a schematic a looooooong time ago, but it doesn't seem to be accessible.

What's the best way to do this? And no, they don't want to use a transmitter.

Pat

RE: 40-180 phono plug - radiodale - 04-07-2020

http://www.nostalgiaair.org/pagesbymodel/336/M0013336.pdf

Add a spdt switch at top of volume control which in one position connects cap 38 to vol control 42. Add cap to to other position and route to an input jack on rear panel.

RE: 40-180 phono plug - Ron Ramirez - 04-07-2020

Here it is:

https://philcoradio.com/phorum/showthread.php?tid=2095&pid=13406&highlight=peter+balazsy#pid13406

Scroll to the bottom of the page.

RE: 40-180 phono plug - Patrick - 04-08-2020

Thank you Ron and Dale.

RE: 40-180 phono plug - Patrick - 04-08-2020

One other quick question, Ron. Am I correct in assuming that this method would eliminate the need for the spdt switch that Dale mentioned?

RE: 40-180 phono plug - Ron Ramirez - 04-08-2020

Let's just repost that modified 38-40 schematic here for clarity.

[Image: https://philcoradio.com/images/phorum/Phorum_Stuff/3840mod.jpg]

This mod uses a closed circuit 1/8" (3.5mm) stereo jack instead of an RCA jack. The jack takes care of the switching so you are correct, no additional switch is needed with this design. Just make sure you wire it up correctly.

I believe the 1/8" jack was chosen to not only provide the automatic switching, but also to better match the input from an iPod or other MP3 player. You can also use this to add Bluetooth capability to your radio.

RE: 40-180 phono plug - Patrick - 04-08-2020

As always, your help is invaluable. Thank you!

RE: 40-180 phono plug - radiodale - 04-08-2020

Phones must be terminated with a 100 Ohm resistor in each channel. Bluetooth needs 1000 Ohms in each channel.

RE: 40-180 phono plug - Patrick - 04-08-2020

Could you expand on that? Thanks.

RE: 40-180 phono plug - radiodale - 04-08-2020

Left and right channels must be added to together since you do not have a stereo input. See attached:

RE: 40-180 phono plug - Patrick - 04-08-2020

So how would that then affect Ron's schematic?

RE: 40-180 phono plug - radiodale - 04-08-2020

There are three terminals on the 1/8 in. jack. One is for left and one for right. Put one resistor on each and connect the two loose ends together, then attach capacitor. Third terminal is ground. It is less complicated than Ron's schematic shows.

RE: 40-180 phono plug - Patrick - 04-08-2020

Thank you, sir. Much appreciated.

Pat

RE: 40-180 phono plug - Steve Davis - 04-08-2020

Yes but, the idea behind Ron's circuit is that it automatically disconnects the radio's audio when connected.

Steve

RE: 40-180 phono plug - Ron Ramirez - 04-08-2020

Thank you, Steve.