Printer Friendly Forum Posts - Big problem that does’t make sense, deck

Hi everyone, i'm going nuts ! posted_image

I've been trying all night to figure out what is wrong with my buddy's system. (Pionner DEH7600MP, MTX RT202 amp)
The problem is that his "sub out" is going wacko: pops and rumbles when turning on and changing tracks and sounds like a bunch of rumbly messed up bass.

I have tried everything, litteraly, to find what is causing the problem. Here's what i tried:

Diffrent RCA wire - same thing - RCA wire not the problem

Diffrent source (from my deck inside my car) works perfect - amp not the problem

Put his deck in my car - works awesome - his deck is not problem

Put my deck (DEH5500MP that works 100% in my car) in his car - exact same problem, problem defenetly not his deck

Tested all wires with meter - Everything normal when on and when off (ON:yellow 12v, red 12v, blue 12V - OFF:yellow 12v, red 0v, blue 0v)

Grounded the casing of the deck - nothing changed

Tried a diffrent source for the turn on lead for the amp - same

cut the harness and rewired it - nothing changed

cut the power wires (yellow red and black) from the harness, connected the yellow to a wire coming directly from the battery, the red connected to a acc relay that i just installed and the black to a nice solid bare metal ground, and with the rest of the harness NOT connected in case speakers were interfering - results....same damn thing !

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Speakers connected to deck works perfect
rear RCA out WORKS
front RCA has that problem
sub out, the same
Deck show no signs of malfunction
Remember that both decks work 100% in my car and has exactly the same problem in his car
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His car, 90 prelude
my car 98 corolla
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If someone could help me out with this, it would be greatly appreciated. Thanks for your time

- Nick

Try regrounding the deck and the amp. Also you said its a popping noise right? Find out if it happens with the car running and also when its just sitting there with the ignition on. If it is only with the car running it could be the spark plug wires. A bad connection or a pin hole in one of the wires can cause a popping noise when runnning an amp.

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double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

Make sure any wire bundles that are behind the installed deck are secured out of the way so that they don't touch the deck casing or the RCA's. Make sure the RCA's aren't bent or touching anything when the deck is installed. Test by running a different deck ground directly to battery with deck out of installed position...then into installed position.

If you don't find the solution there, run separate RCA's over the seats through the car to the amp to isolate that possibility.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

did you try a different amp? that sounds like the only thing that you didn't change. make sure your gain settings aren't too high, thats probably not it, but somthing minute like that will cause more problems that you'd think. on thinkg that also comes to mind that was suggested to me by one of kickers tech guys is that a sub may have a small bad spot on it's coil and when it's at rest it shorts. that would be extremely out of the ordinary, but possible. the tinsel leads could also be bad and cause a problem. try changing the subs. also, running another battery ground is never a bad idea.

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It sounds like either an amp ground issue, or a gain issue.

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My ex once told me I have a perfect face for radio.

im thinkin gain too...

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Canadian Auto Sound
Starting Installer

I greatly appreciate the help everyone but it looks like there's a few things in my first post that has been not been looked at.

When i was rewiring the deck, i had the deck on my lap with the harness streched out attached to it. I also tried moving around the harness to see if it had any affect, nothing changed

It's not a gain issue, when i connect the rca from my car's amp rca output to his amp rca input, the gain behaves normaly. When it's connected to the deck inside his car, if i turn the gain beyond 1/4 there's some sort of feedback (basicly a loud constant humming rumble).

The poping noise is not "thump", it's like a series of soft "pomp pomp popopomp" when the deck is working (reading the cd) it's not loud at all but still an indication of a problem.

could it be the amp's grounding somehow interfering with the deck? The only thing that seems to work is when i connect my deck which is entirely from a diffrent electrical system which it could not interfere. Does this make sense?? The amp in his car is solidly grounded on a bare metal surface.

Today i'm gonna try to connect the deck straight to the battery see what happens. I'll post the results.

Please look clearly at my first post before replying

Thank you very very much for your input everyone. I greatly appreciate it.

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oh, sorry i forgot to add
this happens with the car off or on. doesn't change

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The symptoms you describe in the post above indicate your amp gain is too high. Plus I suggest NOT using teh factory ground for the HU but connect the HU ground wire directly to the chassis.

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I strongly believe that it's not the gain, when running from my car, the deck works perfectly on his amp. I can turn up the gain to a resonable level w/o any defects or feedback.
Also, i don't understand why the rear RCA out works but the front RCA out and the sub out has that problem.

In my first post, i indicated that i ditched the farctory harness all together:
"I cut the power wires (yellow red and black) from the harness, connected the yellow to a wire coming directly from the battery, the red connected to a acc relay that i just installed and the black to a nice solid bare metal ground, and with the rest of the harness NOT connected in case speakers were interfering - results....same damn thing ! "

There's something in the electrical of his car that i just can't put my hand on. I'll try a few things today and post them.

Thanks !!

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OK, so let's be clear: You have installed the same amp and same HU in another car without issues? Then I suspect a bad ground in the vehicle. Assuming your amp ground is good, try cleaning both battery terminals with a wire brush and then baking soda and make sure the engine ground strap is solid and not rusted.

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i'm out of ideas
i tried even more stuff today, still same damn crap.
Grounding the amp didn't help, i ran a booster cable to ground the amp.
I tried his deck in my car with a rca going to his amp (in his car) and it didn't give me the feedback but the signal was very weak. the odd thing is as soon as i plugged in the RCA for the speakers (on rear out) the sub out came to life and was working like normal :S i tried many other configurations and nothing changed. Either way, no matter what i do, if any deck is running in his car i get that problem. I'm about to set this car on fire.

Next sunny day i'm gonna take the damn thing appart, i'm gonna ditch the factory harness forever, run new wires, new relays, new everything.

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Take your car to a professional install shop in your area and pay for some help.

Based on your most recent post, you may have a defective HU. But it's time to get help.

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I'd imagine it would have to be something in the car such as bad ground or low impedance maybe even grounded spkr lead. I was gonna say bad deck but if any deck installed into the car has the same problem this rules that out.

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Tell the Snap-On guy I'm not here!

Internal fault with the ground plane of the Pioneer cd player. Replace the cd player or have the problem fixed at a repair deptot. Not the first time I have seen nor heard of this problem.

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Top Secret, I can tell you but then my wife will kill me.

I'm gonna try to get a non pioneer deck see how that works out. Also I'll try to get my buddy's deck replaced on warranty. Thats pretty much the only other thing i can do.
Thank you very much forbidden

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i always approach troubleshooting from a " what's the same..what's different?" attitude... you say both HU's act up in his car, yet not if wired in yours where you snake signal into his amp (say a 20' RCA cable) yet if you install the same HU in his vehicle the problem reoccurs... what the same? the HU whats different ? the physical power and ground connections (since signal is now going into the amp on car A (his)) applying this same test, does his original HU work fine when "mounted" in your car but plugged into his amp? if so, whats the same? the HU's... whats different? the power and ground planes from amp to deck.... it sure sounds like a ground loop or possibly an open ground to me.... keep in mind that until the two components are connected to the same ground potential, it's unlikely you'll experience a ground loop issue.....

also keep in mind that every output stage ( pre-amp and powered ) are isolated.... you could easily have burned ground foils on one pre-out but not the others or a bad OP amp for the sub out which will have no effect on the other preouts.... the problem you were describing sounds like servo noise coming from the mecha control PCB or the pre out section....this is usually indicative of an open ground path within one or more individual circuits within the HU......

a last simple test you may want to make is to take a jumper wire from ground and physically connect it to the shield of the RCAs at the back of the HU... if it's an open ground in the audio path that channel may suddenly "come to life"... you then would have to take the HU apart (i'm not saying YOU should do this) and isolate and repair the burned/open ground foil....

of course it's really tough to try to troubleshoot something from a distance ( over the phone, over the net, etc )

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Kevin Gerry
Certified Electronics Technician
MECP First Class Installer

Owner/Installer
Classic Car Audio
since 1979

I have actually had a similar issue, at least I think it was similar.

I had my ground come loose on my amp during testing before everything was bolted tight, and the amp grounded through the RCA's of my deck, surpirsingly this was a Pioneer HU that I was using as well. since a 12 volt ground had passed through my RCAs it fried a nice line in the board of my amp and caused a popping/crackling sound in the deck, when you turn the volume up the crackling gets softer and the subs start to fully respond for short periods of time, but that was just because of the current arcing across the burnt sections of the ciruits which was probably what the crackling and popping was.

I had to replace both my amp and my HU, but as I said this does not sound exactly like the issue you are seeing, but it was a ground issue, and from the sounds of it, it's definetely a ground issue.... but that has already been established.

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eh? what did you just say?

Thanks for the extremely valubable peice of information :D
Just one thing, when you say connect a jumper ground to the "shield" of the RCA, thats the outer rim of the connector right? just want to make sure.
Again, thanks alot for your help kgerry

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yes it's the outer shield... some units use an isolated audio ground which isnt common to chassis ground.. so this may tell you nothing, also if the ground path is open anywhere other than the audio path, again this wont tell you anything... but it's just one of the many things i try when i'm chasing down a problem like this.....

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Kevin Gerry
Certified Electronics Technician
MECP First Class Installer

Owner/Installer
Classic Car Audio
since 1979

I've had similar trouble as well, goes back to my very first install....apparently painted metal isn't a good earth!! Who would've thought huh? The drama ended up being that it wasn't earthed through the body of the car but was actually earthing out through the rca leads itself.

Another drama I had with that car that scared the daylights out of me was when I installed the head unit, I connected the power leads, speakers, antenna and was looking around for a spot to earth the unit out too when I hit power button and the thing came on! I was like Whoa! it's got no earth and it's playing the damned CD! It was earthed through the antenna cable wasn't it? Just goes to show that although you may have an earth, if it's a bad earth you may not know it.

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Check all advice given with a meter

BTW, "earth" is the first thing you should hook up, not the last !!!!

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Kevin Gerry
Certified Electronics Technician
MECP First Class Installer

Owner/Installer
Classic Car Audio
since 1979

Search on my username in this forum and you will see that I recently had issues with a thump noise. I tried the same trouble shooting techniques that you did with the same results. I attacked it again last night and I think I found the problem which, in turn, may be your problem because the symptoms sound the same.

My system can be seen here for reference. My amp was mounted on a sheet metal box and the box was screwed into the sheet metal of the truck which, in turn, grounded the box. The screws I used to secure the amp to the sheet metal box also provided continuity to ground through the amp chassi via the sheet metal box. Also, part of my seat's brackets were rubbing/scratching on the frame of the amp which provided another point of ground. Basically, my amp was grounding in two or three spots at once which, according to tech support at Alpine, can cause the head unit to go in and out of safe mode inducing a thumping noise in the system.

Last night I insulated my amp from the sheet metal box and surrounding seat supports using rubber material. I even put rubber under the screw heads to make sure they can not contact the amp. I checked for continuity to ground all over the amp surface and added rubber until I got zilch, nada, nothing. So far today - no problems. Not even a hint of a thump noise.

I say all of this to ask you to check and make sure your amp is gounding only at one point. That point should be the ground wire. This will avoid any ground loops that will induce popping sounds in the system.

My 2 cents (based on experience).

Mike
posted_image

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2000 F150 Supercab Lariat, Alpine CDA-9831, Polk MMC570 in Doors, One Polk MM2104 Sub, One Polk Carbon C400.4 Amp.

John 3:16

kgerry..one of the first things I learnt when I got my first job in the industry posted_image

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Check all advice given with a meter

overworked2 wrote:

I connected the power leads, speakers, antenna and was looking around for a spot to earth the unit out too

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Kevin Gerry
Certified Electronics Technician
MECP First Class Installer

Owner/Installer
Classic Car Audio
since 1979

overworked2 wrote:

"I've had similar trouble as well, goes back to my very first install".........."Another drama I had with that car that scared the daylights out of me was when I installed the head unit, I connected the power leads, speakers, antenna and was looking around for a spot to earth the unit out too "....

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Check all advice given with a meter

does everyone in australia say "earth" instead of ground, or are you just trying to be trendy? because it's not clever, witty or catchy. just curious. now im done.

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soundmasta: it's really "earth". We in the US say "ground". All in all, if anybody's guilty of being trendy....it's us in the USA. The peoples of other cultures seem to be a little more down to "earth"!

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Just to add real quick. My 1990 Prelude had a noise issue, not one like this but it was a noise through the speakers. I ran the RCA's down the passangers side and the power down the drivers side. Also, when mounting the amp i put Rubber feeties so to speak so the amp wouldnt be connected to the chasis. Also on the ground make sure u sand it down and have no paint where it is. Sorry if I repeated something but this is my experience.

Please, so I don't look trendy, witty or clever.....Just trying to stop further confusion.

Earth = Ground

Bonnet = "hood"

Boot = Trunk

Cutters = Side Cutters

Motor = Engine

Engine = Motor

Speaker = Round thing

Sub = Bigger round thing

Amp = That thing that makes music louder.

Did I miss anything?

oops, now I'm trying to be funny, comical and witty.

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Check all advice given with a meter