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Author Topic: Faulty headphone jack is driving me crazy!  (Read 2965 times)

Kubert

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Faulty headphone jack is driving me crazy!
« on: November 21, 2012, 05:40:03 AM »
So I have a Marshall MG15FX, 120v (I believe) Amp that has a faulty headphone jack. As you all know when you plug headphones into an amp it will mute the amp speaker and direct the sound through the headphones. My problem is that my amp is stuck in this muted mode even with no headphones plugged into it. I was able to get normal sounding noise to come out of the amp if I plugged headphones in and held them in a particular spot, so I know the speaker is working fine.                                           I honestly just want to get rid of the headphone jack since I rarely used it and when I did it messed up my amp, and replacing it seems like too much work for a fairly cheap amp. How would I go about manually unmuting my amp and removing the headphone jack? I've never worked on an amp but I'm guessing if I just pull the jack out it will remain silent. Any help or advice would be greatly appreciated.

Roly

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Re: Faulty headphone jack is driving me crazy!
« Reply #1 on: November 21, 2012, 07:00:54 PM »
Don't tell me - let me guess; this is a plastic jack socket that mounts directly onto a printed circuit board, and just for good measure it doesn't have a nut but just sticks through the panel - right?

How do I know?  It's a classic.  It's Sydney to a brick that the solder joints under the socket have fractured (and/or) one of the PCB traces has broken right there.

Generally these take about ten seconds to fix after ten minutes getting to it and another ten minutes putting it all back together - 'tho sometimes you get lucky and access is easy.

Unplug the amp from the mains.

Remove the chassis so you can get at the rear of the socket.

(Perhaps with a bright light and magnifier) wiggle the socket and observe that there will be movement of, or within, its solder joints.

Generally all that is required is resoldering, 'tho in some cases you need a scrap of wire to bridge a broken track.

If you really want to take it out altogether (which will take a couple of minutes vs ten seconds resoldering) then you will need to inspect the socket and work out which contact feeds the tip, and the built-in switch contact that passes the signal on to the speaker; then bridge those two points after you have removed the socket.

Frankly I think you will be better off just resoldering the joints.

HTH
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Enzo

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Re: Faulty headphone jack is driving me crazy!
« Reply #2 on: November 21, 2012, 07:22:36 PM »
What he said.   Either your jack has cracked solder, or the cutout contact is sprung (bent).  If resoldering doesn't fix it, why not just change the jack?  Jacks are cheap.   To remove the jack, you'd need to unsolder the old one, then install wire jumpers in place of it on the circuit board.