QuestionQUESTION: I am using a Panasonic CQ-C7401U car stereo head unit. I had it wired up to a 1980 Ford econoline van. (This van is notorious for having bad grounding.)
I had my stereo hooked up with four of the van speakers to the amplified outputs on my stereo. I have an amp and sup hooked to the sub-output rca jacks on the head unit.
I could not find the always on voltage so I wired the 12v from my cigerette lighter to my head units memory line. (The van is old and the wiring has been moved around.)
While driving, the speakers jittered a bit and cut out. I pulled the head unit and checked the fuse, I also connected a speaker directly to the outputs. This resulted in nothing.
It was suggested to me that poor grounding can burn up an amp. I then wired the sub/horn up to the aux out rca jacks on my unit and was able to get a full range of sound. So I am under the impression that the amp is blown.
I have pulled the unit apart and found a bit of brown on a transistor and a voltage regulator.
Do you have any idea what could be blown on the board/what to replace?
P.S. While running off of the Aux output, the stereo turns down and shuts off about every ten minutes. I have since then ran a large ground wire from the head unit to the frame but I have not had a chance to check the effectiveness of that yet.
ANSWER: Sorry, but specific questions about particular models of cars and/or audio systems for them is impossible for any "expert" to answer, as I don't own the car nor the audio equipment. Research on the Web using search engines or call your auto dealer for assistance. Wouldn't want to fry something serious in your car/truck with bad advice, like the computer! Cheers, Wink
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QUESTION: I understand. I was specific to try to aid in a response.
Do you have any idea what would cause a head units amp-ed channels to drop while driving?
Or what would cause the head unit to turn off every 10 minutes or so while in use? When i pop the face off and place it back on, the unit works for another ten. (BY works, I mean the un-ampliphied channels.
I myself am an EE/CE co-op student and have a bit of experience. I intend to tear apart the head unit and replace the bad parts.
Thank you for your response.
- Mike
AnswerHi Mike,
Oh, I very much appreciate the detail you went into on your question! If only the other 95% of the folks did such an excellent and thorough job. The problem comes down to, as said, that we have a hard time answering things that end up being specific to certain automobiles and/or audio gear.
Since you mention you're and EE student, then I think you should go ahead and dig into the head unit - the worst that can happen is that you're left with a still-broken unit that you need to replace! And you'll probably learn a bunch in the experience.
The hard part is that these units are almost, if not always, impossible to get parts for except for discrete components like caps, resistors, etc. Sounds like you're thinking there's a blown transistor or capacitor (cap), if it's brown it sounds like a cap to me. You should be able to figure out the type and just buy a replacement, and try putting that in.
What bugs me is the cutting out of the AUX and how it jittered when you were running it - it really sounds like either some sort of grounding problem, or a cap that's not fully blown but not working to spec. So I'd be looking at that, and at the power supply and the step-up transformer.
That's my guess as to why they were dropping, other than the other two obvious ones: bad grounding and/or an exposed wire where the driving causes it to work then a bump knocks something loose or something exposed that's grounding out. I've had problems with both in my cars: not grounded properly, or having a wire that would hit metal on the car and ground out - that used to blow fuses for me.
The 10 minute turn-off sounds like some kind of heat sensor that's turning off the unit because it's overheating. It could be there's not enough air circulation where you have it installed, or grounding problems that are causing it to overheat. Most likely it's cutting out on purpose to keep it from melting itself. This is common in most audio gear, automotive or not, in the last decade. Popping off the face panel is like rebooting a computer, so you're reseting it.
Good luck with working on it. Look at it as an assignment and learn as much as you can! The difficult part is that getting replacement boards or service manuals/schematics for automotive audio gear is impossible, which is why most people end up just tossing the stuff, since having a pro fix it is more expensive. Which is a shame, because we're filling landfills with car audio systems. Anyway, hope you find the part, be careful in all your wiring, and remember that too much grounding can never hurt! Cheers, Wink
