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Crossover troubleshooting...

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Manchice

New Member
Hello everyone. I'm a real noob when it comes to electronics, but I'm in a situation that might be easily/cheaply fixed by a bit of circuit board troubleshooting, and I'm actually quite interested in learning how it all works in the process. I've got a basic understanding of ohm's law and magnetism, as well as a Digital Multimeter. So if you're interested in helping, here's the story.

I installed a set of AudioBahn ABC680V component speakers in my car. One half stopped working, so I did some mixing and matching and determined that there was something wrong with the 2-way crossover that fed the midwoofer and tweeter. Someone on a car audio forum mentioned that it may be something I could fix on my own, and I'm willing to try, because if all else fails I'll just sacrifice the extra twenty bucks it would cost to buy a new pair. I've done some basic testing with my DMM, and although I don't really know what I'm talking about, some of the results don't really seem to make sense. I would assume you would find continuity between each of the positive and each of the negative terminals, but the positive tweeter terminal shows continuity with all three negatives instead of the other two positives. If anyone thinks they might know what's wrong, please respond with your suggestion. I'll be up for a while and I've got a good enough camera if anyone would like to see images of what I'm working with. Thanks for your help.
 

Sceadwian

Banned
Continuity is not guaranteed through a diode transistor or capacitor, some of the better audio folk's here might be able to help you better but some decent in focus pictures of the circuit board (both sides) would be helpful. The first thing you do before you touch the multimeter is very carefully go over the board and look for scorch marks or leakage from any capacitors, simple lose connects that type of stuff.
 
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Manchice

New Member
Here ya go. I did my best to find any scorch marks, leaks, or loose connections, but everything appears fine, at least to your average person. I noticed a couple of the connections look a little sloppy underneath, so I included a couple pictures of some crowded areas...











Hi Res: Front, Back, Terminal Area, Switch Area, Terminal Sequence
 
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Manchice

New Member
I decided to go out and re-test everything just to be sure. At first I had thought that no sound was making it through the crossover, but this time I realized that the midwoofer half of the output is working just fine. I'd assume that means the issue lies in the tweeter part of the circuit. Just another little bit of info you guys might use while diagnosing...
 

Sceadwian

Banned
Everything looks fine, it's not exactly a complex circuit. I'd replace the caps and see what happens they may have just dried out over time, how old is the board? I'm not sure how or if you could test them in circuit. I'm not even sure what that encapsulated part at the top left of the board is. Maybe someone else can take a better shot at it.
 

Manchice

New Member
Thanks for your help so far. I purchased this set about 8 or 9 months ago from an internet site, so I really have no idea about its actual age. I think I'll wait and see if anyone thinks they might see a definite issue with the circuit before I start tearing it apart. But I still appreciate your time.
 

Sceadwian

Banned
I'm a little surprised no one else has posted.
Although I do HIGHLY recommend you shrink those images down edit your image post and put them up so they're a bit more reasonably sized.
 

audioguru

Well-Known Member
Most Helpful Member
Did you disconnect the tweeter and measure continuity that it is not burned out?
 

Manchice

New Member
No need. I have both the speakers and tweeters wired all the way back to my trunk, so its very easy for me to mix and match. This morning I went out and used the one working crossover to test both sets of speakers, as well as both the left-front and right-front speaker channels on the amp. They're all good. I haven't yet continuity tested the working crossover to compare to the broken one, but like I said, the input and midwoofer terminals still work, and it just so happens that the non-working tweeter circuit is the one that reads continuity between the positive and negative terminals. This would lead me to believe that there's a short somewhere right in that circuit, and although it might be simple circuitry to you guys, I actually have no idea what's going on in that board. I'm a budding auto tech guy. Electrical might be in my future, but I've still got a long way to go.
 
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Manchice

New Member
This is going to sound like a very elementary question to a lot of you, but like I said, to me, circuit boards look about as familiar as Russian, and I'm viewing this as a learning experience. Do the different partitions on the back side dictate which soldering points are essentially spliced with each other? In other words, does each section act as a common feed for whatever connected components are later on in the circuit? I've been examining it and trying to learn what I can from simple deductive reasoning. Things like capacitors and diodes have been mentioned, and although we touched on the theory behind each of those parts at tech school, I couldn't point out which is which on the front side, nor could I explain the role each one plays in the function of the crossover. I'm still working on the basics. Thanks again guys. This is really interesting.
 
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