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Keyboard Amp Issues


Tothedisco

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I currently have in my possession a Behringer Ultratone k3000fx keyboard amplifier, given to me by a friend to fix as I have some experience in electronic repair.

I'm aware alot of people will write off behringer as cheap unreliable equipment, but honestly I've been quite impressed by this amp.

Anyway the issue is there is no sound from the 15'' woofer, but there still is from the tweeter. I've put a multimeter across the terminals of the woofer, no continuity and no resistance reading.

 

I'm assuming that this is a broken/blown speaker, which can be replaced with the same part; however I would appreciate some confirmation of this before I go and order the speaker for it, if anyone could provide this.

 

Many Thanks

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Another 'quick & dirty' method to check the woofer is with a 9v battery, but make sure it is disconnected from the amp!!!!

When you connect the battery the cone should move in or out, if not, try waggling the cables between the terminal block and the actual cone, if they are accessible. Don't hold the battery on if the cone does respond as they don't really like DC up 'em.

If the cone responds to waggling the wires, then you may get away with just soldering the wires. However the chances are that the driver is knackertated.

 

Don't be trying this method with little speakers or tweeters/horns, they won't like it..... like I said it's a quick'n'dirty method.

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It does sound like the speakers burnt out but test the output of the head with a multimeter to be sure your problem isnt up stream.

 

To expand on that a bit, if you power up the amp and put a voltmeter across the woofer terminals you shouldn't see any more than a few millivolts. If the bass amp is blown up then you'll likely see a lot of DC across it. Is this a dual amp unit (i.e. one amp for the tweeter and another for the woofer) or a single amp with a passive crossover to separate the signals?

 

Dave

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