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Home stereo stopped working possibly has burnt out voltage regulator? Answered

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Greetings,

My Altec Lansing home stereo stopped giving out sound.  There is still fuzz audible from the speakers, but there is no musical sound whatsoever coming through the speakers.  It is a simple stereo but with good sound.  It has one input Jack which has always been loose and finicky; as long as I carefully plug into the Jack and make sure it is a good connection, the stereo has worked fine.  One day however it suddenly stopped giving any musical sound.  I decided to open up the stereo and look inside.  First I tried bypassing the input Jack since I suspected that was the problem.  Bypassing the input jack however made no difference, there was still zero audio signal coming out of the speakers (still only the buzz).  I then looked around on the motherboard to check for any oddities. Everything looked normal except for one Voltage Regulator.  It is a L7809CV.  It has three prongs and a built in heatsink. The point at which it connects to the motherboard is slightly burnt looking as it is discoloured. In the upclose picture you can see two voltage regulators, the one on the left is the one which appears burnt. I was thinking this is likely the culprit. 

Would anyone on the forum have any feedback to offer.  Do you think this is the problem, and would replacing the voltage Regulator likely fix the amp?

7 Replies

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Josehf MurchisonBest Answer (author)2015-07-20

That looks over heated check to see if you are getting 9 volts on the output.

Is the other voltage regulator a L7909CV?

You can get a replacement and the datasheet here:

http://www.mouser.com/Search/Refine.aspx?Keyword=L7809CV

If that link doesn't work go here and search the part number:

http://www.mouser.com/Electronic-Components/

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ootagun (author)2015-07-28

I wonder though if it has been burned out, would replacing it fix the problem? Might there be a different problem causing the voltage regulator to overheat?

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rickharris (author)2015-07-22

It is quite possible that the reg has un-soldered itself from the board as it over heated.

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ootagun (author)2015-07-21

Thanks for the replies. I'll check the output on the Regulator and go from there.

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Downunder35m (author)2015-07-20

Well, it was definately getting hot, but that can be a normal operating sign.
Without testing for defect components there is little chance of fixing.
Sure you can replace it and test but if the fault is caused by something else you start all over.

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