stereo receiver blowing fuses


  #1  
Old 02-27-04, 09:52 AM
jimfh
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stereo receiver blowing fuses

i have a 26yr old technics receiver,that blows the right speaker fuse as soon as i turn on the receiver. we also have our tv wired into it for surround sound,can someone help me to troubleshoot this problem?i miss my my oldies!thanks!
 
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Old 02-27-04, 01:50 PM
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There may be an internal fault with the output stage of the right output which could be causing this. Couple of possibilities I can think of.

1. Most output stages incorporate a slow turn on circuit that connects the output transistors to the speakers after a time delay. Most amps will generate an output voltage spike when turned on while the output transistors settle down to the quiescent state. The slow turn on prevents the speakers or the fuse from blowing. If this has developed a fault the turn on spike can blow the fuse.

2. Most amps have two power transistors driving the speaker - commonly called a push-pull pair. If one of them has failed and the collector-emiter junction shorted the output will be at the high/low rail and this could cause the fuse blowing. Also one of the driver stages could have failed and could be foring the output transistor high or low. Way to check this is to measure the voltage at the output with a voltmeter. If it shows a fixed value like 20V this would point to such a fault.

In both cases troubleshooting at the circuit level will be required.
 
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Old 03-09-04, 06:10 PM
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If you've recently changed or moved your stereo set-up look closely at your speaker wires. Make sure that there is not a fine thread of wire shorting the two speaker leads.

If that does not do it, you are in for some electrical engineering stuff. An old receiver like that is pretty easy if you are into electronics repair. If you don't know a resistor from a transformer than I'd throw it in the garbage and buy a new one.
 
 

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