How to wire a five prong 3.5mm input jack into a portable ra

mjl1297 · Joined: 17 Jun 2006 Posts: 22

I'm wiring an input jack into an old portable radio. It has five prongs on the bottom as opposed to the three you generally see on a 3.5mm stereo input jack. I do have five wires to connect to it but I'm not sure which one goes to which prong. Here are links to the schematics on this old GE radio--

http://www.4shared.com/document/X_64HEVI/schematic_20080505_0002.html
http://www.4shared.com/document/0axfHLIs/schematic_20080505_0001.html

and I'm wanting it so that when I move the selector switch to the cassette position and plug in my cable it will disconnect the tape player and allow the signal being input to come through the speakers.

Iv'e had this wired once already but I recently took the radio apart because one of the connections came loose and as I was dismantling the box the wires separated from my input jack. I actually thought I had a post in this forum from the time I wired this but I can't seem to find it.

Just curious but is there no way to use the input jacks for the external microphone on this unit to route the signal for input from a mp3 player? They are already hardwired is the reason I ask.

Please help as I'm stuck for the moment. If you need additional information let me know.

vtech · Joined: 08 May 2006 Posts: 1264 Location: USA

Not sure what 5 wire inputs are you talking about? I'll try to explain the signal path; When you say an input, it is usually 3 (as you mentioned yourself). You'd need left, right and ground which is usually common to both channels.
When you are going to use what is referred to as standard "line level" input, it is not necessary to provide pre- amplification as the signal has already been conditioned. As in example, an output from a microphone or a tape head is much lower than lets say an output from a cd player or mp3 player which are already amplified to some degree. This has to do with the impedance of the said device.

If you look at your posted schematic, it is easy to see the path; you have a main amplifier(IC5) that gets its audio signals thru pins 8 and 13 from connector FS2. Right below, FS2 is connected to FC2 which gets the L,R (EQ conditioned)signal from the pins 1 and 3.
Backing up the signal path, the graphic EQ (IC6), gets the L,R signals from connector FC1(pins 1,3) which in turn connects to FS1 just above it.
Backing up further, you'll see that Q112 & Q212 are the actual entry points for the signal. Depending on the position of S1, you can select signals from Tape, Radio or CD to be sent thru the processing path to the speakers. Also, in backing up further, you'll see that tape play/rec heads require even more pre-amplification and level control compared to mic inputs at JK1 & JK2.

mjl1297 · Joined: 17 Jun 2006 Posts: 22

Thanks for the response.

Here is a link to a diagram of my 3.5mm jack--

http://www.4shared.com/document/oAzYga97/Input_jack.html

and by the wires I mean that I already have five wires labelled FS1, FS2, FC1, FC2, and GRD. Now to which prong in the diagram above do I attach each one of those wires to?

Guest · Posted: Tue Oct 12, 2010 6:56 am Post subject:

I think I may have it figured out. Connect my GRD wire to prong 1 (top line), FS1 and FC1 to prongs 2&3 on the left of the diagram, and FS2 and FC2 to prongs 4&5 on the right side of the diagram.

Can anyone confirm that?

mjl1297 · Joined: 17 Jun 2006 Posts: 22

That's me in the post above by the way! Very Happy

vtech · Joined: 08 May 2006 Posts: 1264 Location: USA

This may sound difficult but it is not; I can see your picture of the jack. There are no known standards and while your assumption may be correct, I have no way of knowing by simply looking at the tab end of the jack. It all depends on the orientation of what is going in to the jack?
You mentioned you are installing an "input". First you need to know the orientation of the signals on the input plug (left/right/Gnd etc) before you can determine what tabs to use going out of the jack. As far as the audio signals goes, you only need left, right and ground(3 total). Often, there is some sort of a switching used within the jack. It is strictly used as a switch to open or close a connection as the plug is inserted to the jack.

Exactly what are you using as an input signal and how many signal lines.
Is there any sort of number/logo on the jack itself?

Guest · Posted: Mon Oct 18, 2010 3:57 pm Post subject:

It will pass the audio signal from the radio, tape, or CD player when nothing is inserted in the jack's receptacle but when I insert the jack from my mp3 player and move the selector switch to the tape position on the radio the signal from my mp3 player will be output from the speakers.

I can't see any sort of mark on the top of the input jack's housing.

Does that help? Many thanks!

mjl1297 · Joined: 17 Jun 2006 Posts: 22

In the event anyone is interested I figured out the wiring scheme (just as I said above) but I've decided to go with a 6.5mm jack as opposed to the 3.5mm since the 6.5mm has larger tabs and is easier to work with in general. I've decided to use the Switchcraft 14B.