Surround Sound setup help

[uberpubert69]

So I've had this JVC TH-C3 system since it first came out and its worked great for years. Until several years ago where the subwoofer shuts off abruptly during movies or music. specifically when at high volumes or levels of bass. Ive tried replacing it with newer stuff but nothing comes close to having as good as my old JVCs bass. Recently I've seen it could be bad speaker connections, but I have no speakers attached when testing and it still shuts off. The louder, the quicker it does it. It can go up to 60 but I can't even break 45 before it starts to shut off. One thing to mention is when I first was given this I was a child and I butchered the connector port that connects the subwoofer to the receiver. It looks like a S-Video port but it isn't. I was thinking maybe that port is loose as shit and when the subwoofer shakes it jostles it just enough to cut the connection. If that's the case, can anyone point me in the right direction for replacement parts so I can solder a new connector to the woofer? I know it's not a port specific to my model receiver because I remember ripping the cable off my brothers dad when he had replaced his surround sound. If need be  I can take pics but I don't have time to atm. Just hoping someone would know what I was talking about.

Thanks for any help.

[hansolo77]

My sub has an RCA plug on it, not an s-video'like port.   If you can take it apart, you might be ahead to just forego the plug altogether and just solder a cable in directly.  But if it were me, I'd just get a new one.  If you've had it since you were a child, however long that was, it's probably a good investment.

[tthurman]

It looks like this:

It's a mini-din connector, popular for MAC serial interfaces, and a ton of sub-woofer applications when connecting to satellite speakers long ago.  Yamaha used them all the time back in the late 90's early 2000's on the computer speakers, along with everybody else at the time (Altec Lansing, etc...).  It's a straight through cable, and while you could've butchered the connector, if it worked this long I doubt that's the problem, or it would never work.  It's more likely you've got some failing caps on the pcb in the amplifier power supply, hence the reason it's cutting out, and louder it is brings it about more quickly.  If you pull the plate amp out you can see these, but it's anybody's guess which one it is without seeing it.

I'm sure you're not alone, do some searching and see what google turns up, or just pull it out and see which caps are swollen.  I'm betting that's all it is, and you can pickup replacements at digi-key on the cheap, and they have a good selection of caps.  A good local electronics store is another option, just don't pickup some cheap shit like jamicon's.

[uberpubert69]

Thank you both for the response. I'm more convinced that its just an overheating issue because I noticed that there's a fan inside. and the fan is not spinning. And it hasn't spun in years. I just never thought anything of it. Now being somewhat of a computer nerd I understand the need for heat distribution and importance of keeping things cool. I took the back plate off the woofer and I put a regular house fan against it and it lasted WAY longer. I was actually able to listen to a few songs without it shutting off. Though it still shut off. Just means I probably need more direct airflow. And of course a replacement fan is over 30 dollars if Im looking for that specific model fan. 0.19a 12v DC 2 pin PoS...

 

Making progress though!

[tthurman]

I'd still look for caps with dome tops while you got it out.  They are cheap and easy to change, and if you got a fan out, all the more reason to check them as heat shortens capacitor life. 

I've been using a Samsung monitor at work eight hours a day for about four years now that my coworker was going to pitch.  I put about $7 worth of new caps on the power supply board in about an hour one night.

 

[hansolo77]

Wow that link is really helpful with identifying bad caps.  I never even knew of such a thing...

Here's another question for ya..  My woofer has those speaker ins/outs (spring clips) on it too.  What are those for?  Am I supposed to be using them for anything?  The instruction manual I got with my "kit" didn't say anything about them, just to connect the standard RCA cable to the "IN" port on the back.  Are those clips for hooking in speakers, so the signal is actually passed through the woofer before going to the speakers, so it can pick up additional bass, or are those meant for OUTS to get additional amp?  I've never used them, just curious.

[tthurman]

I don't want to mislead you without seeing the sub, but typically a subwoofer will have a LFE (low frequency extension) input that is line level via an RCA jack like your describing, and that's it.  Then others have both the LFE and the high level IN/OUT option as well.

In some setups it is preferred to use the sub in line with the speakers, and that's where these connections you're referring to come into play.  Most people will never use these in my experience, and instead opt for the LFE input, and use the AVR to set the cross-over frequency for better bass management.

 

 

I have some older amps that are way before the LFE/Sub out option was even an option, and in these instances you could opt for the above option, or even use something like a "tape out" line level signal to your sub, but the line level output from these required manual manipulation of the subwoofer gain...so it sort of sucks having to adjust the amp and sub amp volume all the time, hence the advent of the LFE output to remove this nuisance.

[hansolo77]

Oh, so it's more-or-less a "backwards compatibility" feature.  Use the LFE RCA plug if you can, and the speaker lines if you can't.  Cool.  I always wondered lol.

[uberpubert69]

So I've since taken it apart to the best of my ability and I saw no popped caps or anything that looked out of place. I'm still convinced its a overheating issue. Just don't know if I can simply take the heatsink off and apply regular thermal paste to it.

[tthurman]

Not sure about using typical CPU paste, but you already suspect it's overheating, so........

The big thing I would suspect is a CPU is typically under a lot of pressure from the heat-sink mounting, whereas these heat sinks are less so securely attached.  You need something that is gong to stay in place, but without getting hard.

Most of the larger electronics I've opened up use that white thermal past.  TV's had this stuff everywhere in them on the big sinks, and I've seen it in much lesser quantities in stereo amplifiers, but it gets hard over time, cracks and stops transferring well.

I believe this is more ideal for what your doing here, and believe I've actually received some of this with a heat sink once.

https://www.amazon.com/Dow-Corning-Silicone-Compound-Lubricant/dp/B00CAVTGNE

https://www.amazon.com/Dow-Corning-Silicone-Compound-Lubricant/dp/B00D0HVYHI/ref=sr_1_3?ie=UTF8&qid=1502721942&sr=8-3&keywords=Dow+Corning+340