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Old 13th October 2009, 11:57 PM   #1
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Default Help Troubleshooting - 3pc Speakers - Storm blew something!?!

Hi all, i'm new, not sure exactly where to post this.
I have a 3pc speaker, two tweets and a sub, Harman Kardon mod#395. There was a storm recently and now there is no sound output.

I've tested the speakers but i'm not too familiar with testing electrical components, and there are so many I was wondering if anyone knew the easiest way to test the board? There are two LM324 op amps and a TDA 7375 power amp. Fuse is fine, speakers work, power is on! Just no sound... any suggestions or more info needed? I assume there are a few things that are always checked first after a storm, but i'm new to this so that info would save me some time.


Thanks for any help!
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Old 14th October 2009, 01:37 AM   #2
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Checking multiple sources in multiple inputs....
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Old 16th October 2009, 10:13 PM   #3
gfiandy is offline gfiandy  United Kingdom
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First thing to check are the power rails to all the components. Download the data sheets for the parts. Identify the power rails and the range of voltages they will work over. Use a multimeter to see if the right voltages are present on the power rails. If you don't have a multimeter go buy a cheap one, you can get them for £5 and you won't make any progress without one.

If the right voltages are not present try to work out where the voltage rail comes from by following the track back to the regulator for the rail. Then test to see if a voltage is present on the input to the regulator, if it is and there is no voltage on the output you have found your problem. Given that you have no sound at all it is most likely to be a system wide problem like a power rail.

If its not a power rail you will need to start tracking the signal through the system this is quite complex and would be difficult especially for a novice without a circuit diagram. But you could give it a go. Find a loud CD with as constant a sound as possible (A sinewave signal CD is ideal if you have one, sometimes the audio mags give these away) heavy rock is probably a good starting place. Set the multimeter to AC and measure the signal at the output of the source. Then try to track it from the input conector through parts in the circuit till it disapears to identify the part that is faulty. Note inverting opamp designs do not apear to have any input signal if you measure it at the input pin because it is a virtual earth, however if the signal is present on the output you can be happy that it is working.

Regards,
Andrew
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Old 19th October 2009, 02:28 PM   #4
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That's exactly the response I needed, thanks so much!
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