Question about JVC TH-C30 System

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Sub won't stay powered up

JVC TH-C30 will not play sound. Receiver lights up and appears to be playing radio or CD, but no sound. Noticed power indicator light on sub comes on briefly when first powered up, but then goes out within a couple of seconds. Took cover off of sub and found 3 fuses, all of which are good.
Took cover off of receiver, fuse was good there too. If I unplug the cable running from the receiver to the sub and plug it back in the power indicator light on the sub will again light back up and go back out within a couple of seconds. I hear a relay switching when the light goes on and off. I've only had this unit a couple of years and haven't used it but 3-4 times Any help would be appreciated. Lankford

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  • Lankfords Aug 09, 2008

    How would I go about determining this? I have no sound at all. Thanks


  • Lankfords Aug 09, 2008

    Yes, the speakers plug into the back of the sub. The sub speaker read ~4 ohms when I unplugged it from board. The other speakers are ~6 ohms. I only have a 12 volt test light I use on my vehicle. When I checked voltage with a voltmeter where the speakers plug into the sub I didn't read any voltage. nor did I read any voltage when checking the pins that the sub plugs into.

    I tried to send a couple of pictures, but I could only send pictures of a certain size. Thanks

  • Lankfords Aug 10, 2008


  • Lankfords Aug 12, 2008

    I'm not sure I know exactly what part you said works. I assume you're talking about the rack that sits in the bottom of the sub that has circuit boards, transformers and etc.? Thanks


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  • 33 Answers

Well if your getting sound out of your surround speakers then the sub is busted, if your getting no sound at all then your speaker input's are either bad or out... i would test the speaker inputs...

Posted on Aug 09, 2008

  • 2 more comments 
  • Justin Griffin
    Justin Griffin Aug 09, 2008

    if im not mistaken i think your speakers plug in the back of the sub... if thats the case then you can take your sub out of the encloser and see if it moves off the cone or if the coil is burnt up... a coil is the wire that connects from the sub to the sub input where the wires go... if your speakers plug in the back of the receiver then take the casing off and get a light tester, (just a tester that looks like a screw driver but has a light and a gator clip on it,) and test each input...

    If your still having problems let me know and ill send you a pic, of what im talking bout...

  • Justin Griffin
    Justin Griffin Aug 10, 2008 is my email if you want to send those pics.

    i dont know if JVC has a replacement part or if you half to buy a new one... but it has a built in amp/receiver in the sub box... thats is whats bad... its not getting power to the speaker inputs, i have a spear one at my shop for the th-c50 i dont know if it will work but i will test it out on the th-c30 system and see if it works if it does ill tell you more detail on how to fix it... cause the th-c30 is a older system so jvc having spear parts is probley rare...

  • Justin Griffin
    Justin Griffin Aug 11, 2008

    well it will works but its a lil bigger then the c30, the box size is bigger then the c30. but you can also just take the sub from another series like the c40 or 50, and use it, it will run just fine on your system...

  • Justin Griffin
    Justin Griffin Aug 12, 2008

    If you got the cover off the sub, there is a bored back there that has speaker inputs on them, that is the piece im talking about... its what powers the speakers... that part is bad, it could be from 1 of 3 things, either a fuse on there is out, a wire off one of the coils is burnt out or the chip it self has gone out...

    i dont know if you have pic's of your system and of the inside of your sub mainly the bored area but if you do that would help me out alot, cause i could see just what is wrong with it...


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