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post #1 of 7 Old 08-14-2014, 07:49 AM - Thread Starter
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Unknown Problem?

Instead of writing it all out again, here is the link to the post I made in the wrong section, you can reply to either one, thank you for your help.

Unknown Problem?
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post #2 of 7 Old 08-14-2014, 11:10 PM
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trying to understand

Sub does not work on current amplifier in your car

Sub works on different amp

different sub works on current amp

no changes to wiring

correct?

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post #3 of 7 Old 08-15-2014, 12:31 AM
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what i cannot determine, is how you came to the conclusion that your amp is fine... you did not go into detail about that.

also, it would help a lot if you mentioned what equipment you are using. head unit, amp, sub. give brand and model numbers.

also, you mention that you have .3 volts on the RCA's... were you measuring AC or DC ? and does that voltage increase when the volume is turned up ?

it is not hard to find the problem, but you have to give some important info first.
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post #4 of 7 Old 08-15-2014, 02:40 PM - Thread Starter
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AMP is brand new MB Quart FX Series 700W - Confirmed working. - I bought a new one cause I thought mine died originally and I wanted an upgrade anyway, so it can't be the amp.
Sub has been tested in a different car with a different amp and worked.
I am using a Kenwood deck - not sure what model but its 2-3 years old.
I tested power getting 12.3, Remote 12.3, ground is good, re-checked all fuses.


I was testing on DC the 2000m setting it was getting 90~ on low and 120~ when I had the volume turned up.

So in summary, I've tested every single cable and they all are getting power.
I've checked my wiring with the harness and everything is connected.

How it originally died was, the sub just stopped working randomly when I went to start my car, then the next morning I started my car and the sub worked again and I went to double test and turned my car off and turned it back on again and the sub no longer worked and hasn't worked since then. All my other speakers are working, deck is still working. Can you kill the pre-amp but still get voltage from it but no sound?
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post #5 of 7 Old 08-15-2014, 11:59 PM
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MB Quart is a Maxxsonics amp... you can find the same build Hifonics used in their amps. i take it that it is a FX1700 ? being a Maxxsonics board, i would not assume that it is good, even if it is brand new... you get what you pay for, and i have worked on literally thousands of them. including the boards used by Digital Designs, American Bass, Audioque, DC Audio, etc, etc. they are all made by the same manufacturer in Korea and China. the bigger amps being Korea, and most of the smaller amps like the MBQ being China. i have seen them not work brand new out of the box.

you did not explain how you determined the amp was good... did you hook it up in another vehicle ?

know that if you do have the FX1700, it is a 2 ohm minimum stable amp. measure your speaker wires and make sure you have more than 2 ohm load. while that amp can run a little bit lower, it will live an extremely short life.

yes, you can blow out the RCA outputs for the sub on your head unit. people do it all the time by hot swapping the RCA's... in other words, not turning the unit off before unplugging and plugging the RCA's. if your head unit has 3 pairs of RCA outputs, then there are 6 surface mount transistors driving them. 2 of them for the sub. your mistake is you were measuring DC... if you see DC on them, then that means one or more of those transistors are shorted. you should be measuring AC. you should see the AC voltage go up as you increase the volume.

try something... hook everything up except the RCA's, and then use an ipod or MP3 player, phone or whatever with an headphone to RCA adapter, and plug it into the RCA's of the amp. if the amp is really working, then it should play. if it does, then swap the RCA cables. should work, unless your RCA output from the head unit is bad.

if it does not play, then the only thing it can be is the amp. ( since you said the speaker is tested good )

but before you do anything, make sure that your RCA's are plugged into the input RCA's of the amp... not the output RCA's. seen that many times...
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post #6 of 7 Old 08-16-2014, 06:55 PM - Thread Starter
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I cannot confirm that the amp is perfect, but I also swapped it out with a buddies alpine 500 mono and still nothing. So two brand new amps have been tried.

Yup, I went and tested the sub with multimeter and it says its 4 ohmz. Does that mean anything in terms of it's functionality?
I went and bought the 3.5 to RCA and tested that, everything hooked up as normal, but using the IPOD with the RCA adaptor and got no sound.
I measured the RCA coming from the deck in DC and it shows voltage, doesn't that mean the deck is shorted out like you said above? I also measured it in AC and got 9.3~.
But since the IPOD thing didn't work, and i'm recording DC voltage on my meter, wouldn't it be highly unlikely that I blew my sub and my headunit?

I only tested the sub by using on my friends 450 watt old ass kicker amp, and my other friends 4 chan amp, both played through the sub but pretty quiet, I figured it was just cause the lower wattage and the amp was still powering a few other small speakers. But maybe it just wasn't reaching enough load to shut the sub down? Because my friend said "Just because you test it on another amp doesnt mean its all good the other amp might have been 1ohm stable and not shutting down."
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post #7 of 7 Old 08-17-2014, 02:04 PM
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4 ohms is fine. that amp puts out 350 watts RMS at 4 ohms. you measured at the speaker wires that connect to the amp, right ? any amp will run a 4 ohm load. i have no idea what your friend is talking about a 1 ohm load... you have a 4 ohm load.

if the ipod did not work, then the amp is not working.

9.3 volts AC is too high. you probably are not measuring right.

you did confirm that you are plugged into the "Input" RCA's and not the "Output" RCA's right ? that amp has both, and will not work if plugged into the wrong ones.

you never mentioned how you have the amp set up... try this. going on memory of what the amp has:

1. turn the Level halfway up.

2. turn the Low Pass around 80Hz

3. turn the Subsonic all the way down to 10Hz

4. Bass Boost does not matter... but turn it around half way.
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