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Amp with no sound

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(@akflyingv)
Honorable Member
Joined: 18 years ago
Posts: 406
Topic starter  

So today I got my new amp in from UPS. I got it from a store on Ebay, and the guy had over a 100 positive comments and 4 bad ones. First thing I do before I plug it in is give it a quick look over to make sure nothing is busted, everything looks fine. I plug it in and turn it on, then put it in standby to let it warm up a bit. Let it sit for 5 or 10 mins, and then plug my guitar into it. I had already turned all the knobs to about 12 o'clock, I took it off standby and strum the guitar and nothing comes out. So i tried another guitar and another guitar cable, still nothing is coming out. The power switch is lit up and so are the tubes so I know its getting power.
Everything looks fine, does anyone have any ideas as to why it isn't working??? I'm sure it isn't something very big and I may have just overlooked something.


   
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(@akflyingv)
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Joined: 18 years ago
Posts: 406
Topic starter  

Just so you know it is a Marshall JCM 900, 50w dual reverb combo.


   
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(@jtb226)
Estimable Member
Joined: 18 years ago
Posts: 106
 

did you check to make sure the speakers were plugged in? i think on a marshall you can unplug them. not sure though as i'm not too familiar with the amp

"Heavy decibels are playing on my guitar
We got vibrations comin' up from the floor
We're just listenin' to the rock
That's givin' too much noise....
Rock and roll ain't noise pollution"
~AC/DC


   
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(@ricochet)
Illustrious Member
Joined: 21 years ago
Posts: 7833
 

I've also fussed around wondering why a silent amp wouldn't play and found my guitar volume turned down. Or a cable had gone bad.

"A cheerful heart is good medicine."


   
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(@akflyingv)
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Joined: 18 years ago
Posts: 406
Topic starter  

I tried 2 cables that work on my other amp, checked my guitar's volume and it was up all the way. I don't know exactly where the speakers plug in but I followed all of the wires that I could see and none were unplugged. There was a wire that came with it that was plugged into the Loudspeaker output jack that wasn't plugged into anything. In the manual it says it is to link cabs so I'm assuming it wouldn't be used for anything at this point.


   
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(@ricochet)
Illustrious Member
Joined: 21 years ago
Posts: 7833
 

Unplug that thing! It's probably plugged into a shorting jack that connects the internal speaker(s) only when no external speakers are plugged in. Playing an amp with no speaker connected is risky. May puncture the insulation in the output transformer primary winding, leading to shorts immediately or later.

"A cheerful heart is good medicine."


   
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(@akflyingv)
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Joined: 18 years ago
Posts: 406
Topic starter  

I unplugged it right after I plugged it in. It was only plugged in for maybe 1 or 2 minutes while the power was on, but it was on standby for most of that time.


   
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(@slejhamer)
Famed Member
Joined: 19 years ago
Posts: 3221
 

This looks like a 1x12 version of that amp, but I think you need to connect that cable from the speaker out to the speaker as shown here:

I *think* one is for connecting the internal speaker and the other for an external cab. If one doesn't work, try the other.

"Everybody got to elevate from the norm."


   
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(@akflyingv)
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Joined: 18 years ago
Posts: 406
Topic starter  

Yeah, that is the wire that I was talking about. At the bottom it is split into a red wire and a white one, where does each one go??
Sorry for posting if this is a common thing, but i had no idea what was wrong, kinda freaked me out!


   
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(@demoetc)
Noble Member
Joined: 21 years ago
Posts: 2167
 

Hmmm...with the amp off long enough for everything to cool maybe gently push the tubes upward into their sockets? One of them might've gotten a little loose in transit.


   
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(@slejhamer)
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Joined: 19 years ago
Posts: 3221
 

Yeah, that is the wire that I was talking about. At the bottom it is split into a red wire and a white one, where does each one go??
Sorry for posting if this is a common thing, but i had no idea what was wrong, kinda freaked me out!

Those wires most likely need to be connected to the lugs on the speaker. One lug should be marked with a +, the other with a -. The wires should have ends that push into place on the lugs with a bit of wiggling.

If you hook them up the wrong way, the wiring will be out of phase (I think that's what it's called) and the sound will be somewhat trebly and thin. Just swap 'em and it should be good.

"Everybody got to elevate from the norm."


   
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(@akflyingv)
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Joined: 18 years ago
Posts: 406
Topic starter  

It splits into two different wires, one red and one white. There are two lugs available on each speaker, does it matter which speaker I connect them to? And which wire would be the + and which the -. I would assume red to be the +, and white the -.


   
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(@slejhamer)
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Unless someone familiar with that particular amp chimes in, I suggest getting in touch with the person who sold it to you and asking for the correct configuration.

Wiring the speakers incorrectly (i.e., series when they should be parallel, or vice versa) could cause problems for the amp. With a 1x12 it wouldn't be much of an issue; but since there are two speakers in yours it can be more complex.

"Everybody got to elevate from the norm."


   
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(@akflyingv)
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Joined: 18 years ago
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Topic starter  

Ok.....I finally got it working. It was real simple, that wire just plugs into one speaker's lugs. Thanks to everyone who answered me, I thought I got ripped off but it works perfect.


   
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(@slejhamer)
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Joined: 19 years ago
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Glad it's working, but is the other speaker connected? If not, you're likely going to have an impedance mismatch with the amp ... not good.

"Everybody got to elevate from the norm."


   
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