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 Post subject: SX 424 fuses
PostPosted: Oct Mon 28, 2019 6:29 am 
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Joined: Jan Mon 24, 2011 7:21 am
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Location: saint clair shores, michigan
I picked up a Pioneer SX 424 today. The line cord was cut and two fuses blown. There are 3 fuses on the back panel. One is labeled AC lines and the others right and left protection. Both protection fuses are blown. Are these fuses protecting the speakers?
Should I slowly power it up using a variac?

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 Post subject: Re: SX 424 fuses
PostPosted: Oct Mon 28, 2019 12:56 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Utica, NY 13502 (USA)
I looked at the schematic available here:

https://www.hifiengine.com/manual_libra ... -424.shtml

Those fuses are in series with the power supply going to the left and right power amp stages and not necessarily for speaker protection. I would test the output transistors for shorts before applying power even if using a variac.

Dave


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 Post subject: Re: SX 424 fuses
PostPosted: Oct Mon 28, 2019 7:31 pm 
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Joined: Nov Sat 07, 2009 11:37 pm
Posts: 2214
Location: Sayreville, NJ 08872
I agree with Dave. Those 2 fuses are there to protect each channel. If they are blown, most likely the output and/or the driver transistors are bad.

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 Post subject: Re: SX 424 fuses
PostPosted: Oct Mon 28, 2019 10:40 pm 
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Joined: Jan Mon 24, 2011 7:21 am
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Location: saint clair shores, michigan
Thanks, guys. I got the schematic.

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Bright antennae bristle with the energy - The Spirit of Radio


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