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Loud hum and no sound output

Started by solochoe, October 19, 2008, 03:02:01 PM

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What is producing this loud hum?

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Total Members Voted: 1

solochoe

I recently bought a used Laney Linebacker amp that did not have power at the time.  I was assured that it only need new fuses.  I replaced these fuses only to find out that there is only a loud hum from the speaker and no sound output from a guitar.  Can anyone tell me what the problem could be.  I've never done any repair work to an amp so this is all new to me.

tonyharker

As this is a transistor Amp I would think that the output has been shorted at some time and blown the output transistors - likely as the fuses have blown!

Tony 

Jack1962

If the amp has an effects loop check and see if you get signal come from there if so the preamp is fine it is in the driver or power amp stage. Blown fuses can be caused by a many different problems.

                                     Rock On

Enzo

Before you do anything else, watch the speaker cone when you power on.  If it moves one direction then stays there, TURN IT OFF IMMEDIATELY.  That means you have DC on your speaker.  It will ultimately burn up your speaker if left on.  If so, disconncet the speaker until teh amp is fixed.  You can monitor the output with a voltmeter while servicing the amp. 

If you are techie, then disconnect the speaker now and check for DC afterwards.  DC on the output alone won;t blow fuses, but WITH a speaker it usually will.

And as mentioned above, DC on the output is usually from shorted transistors.