[intoflatlines]

I have a cheap Sony transistor radio with a mono 1/8" output jack. I am trying to take the jack out and put in a 1/8" stereo jack, so that I can have sound from both channels. I though it would be simple enough. I planned to take out the jack and put in the stereo one, and bridge the left and right channels.

When I opened the case up, I found that the mono jack had three leads connected to the board. Interestingly, the positive battery lead was connected to one of them, but I couldn't find where the path led it after that. It seemed that nothing else connected to the positive lead and it just ended in the jack, which I know is impossible. I took some pictures of the area, please tell me if you anything about this.

Key:
1 - positive lead from battery compartment
2 - mystery lead on mono jack. It appears to be connected to the positive battery lead via the circuit board.
3 - the left signal lead
4 - ground lead.

I tested the continuity of the three leads on the jack with a stereo mini to mini, and that's how I found out which corresponds with which. #2 does not connect to anything, and 3 and 4 are left and ground respectively.

When stereo headphones are plugged into the jack, sound comes out of the right channel if you turn up the volume very very high, but the imbalance is huge.

I hope someone on here can help me out.

 

[Budgie]

A jack like this will often have a built in switch. It may disconnects the power if no phones are plugged in.
The other possiblity is the jack's switch is used a to kill the speaker in the radio when the plug is inserted.

Check and see if two terminals on the switch short with or without the plug in. For instance- terminal two could short to three or four when the plug is in or out.

 

[pkshiu]

A mono jack like that should have three connections, 1 to common ground, 2 to input, 3 to speaker. If jack is not plugged in, 2 is connected to 3. If jack is plugged in, 2 is connected to headphone and break the connection to 3. (disable the speaker).

THe red wire perhaps go to the speaker, not to battery. Check that!

P.K.

 

[intoflatlines]

Thanks for the replies! Wow, do I feel stupid..

Quote:

Originally Posted by Budgie /img/forum/go_quote.gif A jack like this will often have a built in switch. It may disconnects the power if no phones are plugged in. The other possiblity is the jack's switch is used a to kill the speaker in the radio when the plug is inserted. Check and see if two terminals on the switch short with or without the plug in. For instance- terminal two could short to three or four when the plug is in or out.

Yes, with a plug in the jack the speaker is disabled. With nothing in it, it appears that all four terminals are shorted. With a stereo plug in it, it appears that terminals 1/2 and 4 are shorted.

Quote:

Originally Posted by pkshiu /img/forum/go_quote.gif A mono jack like that should have three connections, 1 to common ground, 2 to input, 3 to speaker. If jack is not plugged in, 2 is connected to 3. If jack is plugged in, 2 is connected to headphone and break the connection to 3. (disable the speaker). THe red wire perhaps go to the speaker, not to battery. Check that! P.K.

You are right. I focused so much on those four terminals that I forgot that the red wire was the positive lead to the speaker, not the battery!!

I need to learn to take a step back and look at the big picture every once in awhile..

Anyway, I am assuming that putting a stereo jack in there won't work especially since it then won't disable the speaker when headphones are plugged in. What can I do to get signal to both left and right channels when I plug a headphone into this thing?

 

[JackH]

Quote:

Originally Posted by intoflatlines /img/forum/go_quote.gif What can I do to get signal to both left and right channels when I plug a headphone into this thing?

There are adapters made for this specific purpose, such as this one at Radio Shack.

 

[intoflatlines]

Thanks for the link but I want to have it built in so I don't have to worry about an adapter or putting too much stress on the jack.

Anyone else have info about how to do this?

 

[plaidplatypus]

Just get a cheap portable stereo radio that has a mono switch on it. In mono mode it should send the same signal to both the left and right channels.