# Speaker fading in and out (Guitar Amp)



## GuitarsCanada (Dec 30, 2005)

Interesting issue here. This Johnson amp that I recently acquired has now started to act up a bit. I have the amp (combo with 1x12) running into a 2x12 extension cab and the combo speaker is fading in and out volume wise. Funny thing is that the 2x12 speakers do not do this. If there was an issue with the amp you would think all speakers would be affected and not just the internal 12" speaker in the combo.

Any ideas on what that could be?


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## greco (Jul 15, 2007)

Have you tried to hook up the internal 12" to another amp? .....Just a thought.

How are the connections to the internal speaker? ...Just another thought

However, somehow I really doubt that the speaker is the cause of the problem...My final thought

Cheers


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## GuitarsCanada (Dec 30, 2005)

greco said:


> Have you tried to hook up the internal 12" to another amp? .....Just a thought.
> 
> How are the connections to the internal speaker? ...Just another thought
> 
> Cheers


I checked the connections to the internal speaker (to the speaker that is) and they are good. I have not tried to take the speaker out and use it somewhere else, I do have some 12" speakers here, I guess I could switch it out and see if its the speaker itself. I changed the 12ax7 tube (the only tube) to see if that was it, still the same. But like I said, if it was something internal you would think that the extension cab would be doing it as well but it remains at proper volume at all times. The internal speaker will die right down to zero volume and then slowly come back up.

The amp runs at 60 watts on its own and then runs in stereo if you add an extension cab. Would the stereo have anything to do with it? Most likely not. If I take out the extension cab it is still doing the fading in and out thing with the internal speaker


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## greco (Jul 15, 2007)

GuitarsCanada said:


> But like I said, if it was something internal you would think that the extension cab would be doing it as well but it remains at proper volume at all times. *The internal speaker will die right down to zero volume and then slowly come back up.*


WHOA...now this IS getting interesting.

cheers


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## vasthorizon (Aug 10, 2008)

Natural/analog tremolo feature?  I keed, I keed.

Have you tried hooking up just one of the cabs at a time?

Maybe a problem with the impedance matching/combination?


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## greco (Jul 15, 2007)

vasthorizon said:


> Natural//analog tremelo feature?  I keed, I keed.


Theese ees no keeding maatter, ******!


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## GuitarsCanada (Dec 30, 2005)

Very bizarre. No crackling, buzzing or anything like that. Just fades out.


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## GuitarsCanada (Dec 30, 2005)

I read somewhere that it might be the send and return jacks on the effects loop, which I have used a few times and am not using right now. Possible remedy is to just plug in a small jumper to close that loop. I will try that


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## greco (Jul 15, 2007)

GuitarsCanada said:


> I read somewhere that it might be the send and return jacks on the effects loop, which I have used a few times and am not using right now. Possible remedy is to just plug in a small jumper to close that loop. I will try that


Interesting....looking forward to hearing about the results of the jumpering.

Another thought...Do you stop playing when it fades out ? (logically you would/might)...Is the speaker warm to the touch? 
How quickly does it "come back up to" volume? 

Can you tell I'm guessing.............you are correct !

Cheers


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## GuitarsCanada (Dec 30, 2005)

I think the effects loop jacks may have been the problem. I put in a small jumper from send and return and the return had a bit of crackle to it. I think they may be dirty. This amp is i very good condition but is still over 10 years old. The amp worked fine for the first week I had it and then I added some effects to it and used the effects loop. That is when I first noticed the problem. So then I removed the pedals from it the other day and it has been doing this weird volume thing. So I read a little snippet somewhere and it said that these jacks can sometimes act up and it tells the amp that there is something there when there is not. So to fix it you just take a small jumper and plug it into both jacks. I think its fixed. Will know for sure after playing it some more but it has not done it again since I plugged that cord in. The previous owner may have never used the effects loop or I triggered something when I did.


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## greco (Jul 15, 2007)

Hope it is fixed with the jumper...please let us know how it turns out.

This is a good thing to be aware of. Thanks.

cheers


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## GuitarsCanada (Dec 30, 2005)

I think we may have solved it. As bizarre as it seems it was being caused by the effects loop jacks. I have been playing it now for about 40 minutes with the jacks closed and its fine. Only other thing could be from a over heating perspective, so I will keep it going here for a bit and see what happens.


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## GuitarsCanada (Dec 30, 2005)

Well I think we may be able to close the file on this one. I have ran it over an hour and it has not done it again since using that jumper in the send and return jacks. The only question that remains would be why the extension cab continued to work when the internal speaker was affected by this. Also, assuming that the effects loop is the problem, what would be the eventual permanent fix? Either a good cleaning or replacing jacks. Either of which is not the end of the world.


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## Gizmo (Aug 7, 2008)

Dumb question, but when you say it runs in stereo, do you really mean stereo? Is this a stereo amp with two independent power amp sections?



GuitarsCanada said:


> ......The amp runs at 60 watts on its own and then runs in stereo if you add an extension cab. Would the stereo have anything to do with it? Most likely not. If I take out the extension cab it is still doing the fading in and out thing with the internal speaker


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## GuitarsCanada (Dec 30, 2005)

It is a 60 watt combo but if you plug into an extension cab it will run 120 watt stereo. It requires the extension cab to run in stereo mode.



> Stereo Operation
> Running the Marquis in stereo will add a thicker texture, and more lush sound to your instrument. The JM60 has an external speaker
> connector located on the rear panel. This is a powered output, which provides an additional 60 Watts of power for connection of a satellite
> speaker cabinet such as the J112. Connecting a speaker to this jack will automatically put the JM60 in stereo mode and provide stereo
> imaging to your effects.


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## greco (Jul 15, 2007)

GuitarsCanada said:


> The only question that remains would be why the extension cab continued to work when the internal speaker was affected by this. Also, assuming that the effects loop is the problem, what would be the eventual permanent fix? Either a good cleaning or replacing jacks. Either of which is not the end of the world.


I would try cleaning them first, personally. If volume from the external cab was fine, it just might be that it due to the way it is wired up internally. I really have no clue...this is way beyond knowledge of circuits.

At least you solved the problem....or it certainly seems like you have.

Cheers


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## Gizmo (Aug 7, 2008)

From the owner's manual...

"Loop Return -	This stereo TRS jack is used to connect from the outputs of an external effect device to the JM60/JM120. It is a stereo input to the stereo power amp within the Marquis."
So it does have two power amps and your problem was with only one side, thats why only the internal had a problem. You probably cleaned the fx loop contacts when you plugged the cable in.



GuitarsCanada said:


> It is a 60 watt combo but if you plug into an extension cab it will run 120 watt stereo. It requires the extension cab to run in stereo mode.


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