Anyone wanna help a Dummie? JVC SK-400 II

RMS 330

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I have a pair of these speakers, sound great especially with a base heavy amp. One stopped working. Like it is disconnected. I opened it up and see this. No wires are loose. Have no idea what I'm looking at but must be a bad resistor or capacitor or other thing I here talked about on AKIMG_20180825_200117.jpg IMG_20180825_200542.jpg IMG_20180825_200616.jpg . I have a mutimeter and a soldering iron and very limited skills. Can I test/troubleshoot something on that crossover and make this speaker work again?
 
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You likely did this, but I just have to ask, did you try connecting the non working speaker to the same channel as the working speaker?
 
Yes. New wire, different channels. One works, one don't. Found this on ebay. they look similar but drive 10" rather than the 8" woofers. Maybe I could just swap them out?
 
I think you blew your speaker. Put your multimeter on the lowest ohms range, and measure between the red wire on the terminal strip, and the black wires attached to the negative terminal. Should be about 8 ohms, but I'm guessing the voice coil is toast, and it will be infinite.
 
I think you blew your speaker. Put your multimeter on the lowest ohms range, and measure between the red wire on the terminal strip, and the black wires attached to the negative terminal. Should be about 8 ohms, but I'm guessing the voice coil is toast, and it will be infinite.

It shows 1.3ohms Happy. Not good right? What exactly is the voice coil?
Does that mean the drivers are still ok. Could I swap it with one of these.
https://www.ebay.com/itm/JVC-SK-500...937225?hash=item3639bd3d09:g:mtcAAOSwfcVUDK03
 
Thanks for the replies BTW, I truly appreciate it. I am determined to at least become a novice at vintage stereo repair.
 
You're not understanding me, I think you blew the woofer. 1.3 ohms means you melted the insulation, and the voice coil is shorted. DON'T hook it back up, or you'll damage your amp. Those things on fleabay are crossovers, which I would be surprised if you damaged the choke. To confirm the woofer is blown, remove it from the cabinet, unhook the wires, and test it to see if it's 8 ohms.

Speaker-Diagram.png
 
OK. so I set the ohm meter to lowest setting, placed a lead on each post of the speaker. It fluctuates between 7 and 8. However, when I test the end of the wires that I detached from the crossover and still attached to the speaker posts , it reads 1.3. Bad wires? BTW, I got no response at all from woofer or tweeter when hooked up.

Hahaha, you guys feel free to have some fun with my technical inadequacies.
 
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Umm, I don't understand how a short like that could happen there. This is actually a good sign, your amp still works on both channels, and the woofer is testing ok. My next test would be to see if the capacitor shorted. The capacitor is the little blue can that says CE 85°C on it. If that measures 1.3 ohms, that's what shorted. In which case, it might have toasted the tweeter.
 
Agreed - That was fortunate. Verify that the speaker is disconnected at the amplifier so that only the speakers and crossover network are being measured. Isolate each speaker in the enclosure and start measuring resistance at the capacitor(s) in the crossover. Anything less than several thousand Ω is probably not good.
 
The capacitor registers nothing on the ohm meter. So do I buy a new one and solder it in

No, an infinite reading is normal for a capacitor. That's not where the short is. Try putting the meter probes in the terminals where the speaker wires go, and see what resistance you get. This makes no sense whatsoever.
 
Below is a picture that may help.

upload_2018-8-26_20-41-21.png

If you are using the lowest range on your Ohm meter, a capacitor will measure as an open circuit. That is show no indication on your Ohm meter.
upload_2018-8-26_20-50-1.png

See the picture above.

Just as a check, measure the resistance between the circles of the same color. This will measure the resistance of the inductors that are labeled L1 and L2. They should measure as low resistances.
 
You likely did this correctly, but when you say different channels do you mean different as in left and right channels, or as in A and B channels as selected by the speaker selection switch on what ever is driving the speakers?

Is you amplifier, receiver or what ever you are using just a 2 channel amplifier, that is just left and right channels or is it something different?

Did you connect your working speaker to the same channel as the speaker that stopped working and if so did it work okay?

Again you may have done these tests correctly, but with a strange situation like yours, it is not a bad idea for those that are trying to help to have a clear understanding of what you have done.
 
I measured the resistance of inductors L1 and L2 (that sounds impressive). It reads .6 between both the teal and purple circle points.
The speaker was hooked up to different amps with different speaker wires with the same result. Nothing. Well maybe a very low distorted whisper.
I went and retested the driver and it actually reads .7 to .8 ohm not 7 to 8 ohm.
So that would mean voice coil short after all?
 
I measured the resistance of inductors L1 and L2 (that sounds impressive). It reads .6 between both the teal and purple circle points.
The speaker was hooked up to different amps with different speaker wires with the same result. Nothing. Well maybe a very low distorted whisper.
I went and retested the driver and it actually reads .7 to .8 ohm not 7 to 8 ohm.
So that would mean voice coil short after all?

Yes, sounds like the voice coil is shorted. If you add the resistance of the inductor, and the voice coil, you get about 1.3 ohms.
 
I went and retested the driver and it actually reads .7 to .8 ohm not 7 to 8 ohm.
So that would mean voice coil short after all?


This is definitely a missing piece of the puzzle.

Yes, if that measurement is correct, it indicates a shorted speaker driver.

It looks like you supplied the woofer with more power than it could handle. This also might mean that the same thing could have happened to the tweeter. It would not be a bad idea to measure the resistance of the tweeter if you have not also done so.

If it measures okay, you can reinstall it in the speaker cabinet, without the woofer and being careful that the loose woofer wires do not short to each other or any thing else, you could carefully connect the speaker to your amplifier and see if the tweeter works and sounds okay.
 
Thanks a BUNCH guys. What took me all day (off and on) to troubleshoot would've taken you 5 minutes to figure out. But I learned a little something. I kept checking in here for replies and doing as instructed. All the while moving my future treasures from the basement up to the spare bedroom. It will now be my testing/listening center.
If the tweeter still sounds good I will install a woofer that I found in the basement and conclude my first project.
Up next will be a thorough deoxit treatment (instructions found here) on the Realistic 2270 I use for testing. Followed by re foaming Technics SB-2680 15" woofers. Then a pile of other stuff.
 
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