# Amp Isn't Lighting Up



## pimpride (Mar 28, 2005)

Hello all, I am fairly new to the audio scene. My brother bought this amp about a year ago, along with some nice subs, which were regretfully stolen, but the thiefs left the amp. A year later I inherit the car, and the nice Pioneer sound system. I want more bass so i look online and get 2 12" Kicker Comps for $90, not a bad deal I think. This is all besides the point though.

Tonight I just got done building a custom subwoofer enclosure, and I go to install everything (all the wires are left over from when my brother had his stuff in there), I replace the fuses, but the amp doesn't light up. WTF?

The amp is an MTX Thunder 251D- http://mtxaudio.com/caraudio/archive/2004amps/thunder251D.cfm . It is a bit lacking the power for my subs, but not by a whole lot.

I am at a loss on what to do now, I have power on the connections for my amp (+, and - wires), and I know the subs are hooked up right. That leaves the remote wire, I'm not sure how to test this, I don't have a volt meter but I could get one if needed.

Any help would be appreciated.


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## captain_shrapnel (Sep 10, 2004)

pimpride said:


> ...
> 
> I am at a loss on what to do now, I have power on the connections for my amp (+, and - wires), and I know the subs are hooked up right. That leaves the remote wire, I'm not sure how to test this, I don't have a volt meter but I could get one if needed.
> 
> Any help would be appreciated.


Without a voltmeter, how do you know you have power? In any case, check the positive power for 12v, if that checks out, turn on your stereo and test the remote line for power, 12 volt as well. If all that is good, be sure you have a solid ground (not a likely problem, but worth checking to be sure), otherwise the amp is fragged. Either get it fixed or just buy a new one.


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## pimpride (Mar 28, 2005)

captain_shrapnel said:


> Without a voltmeter, how do you know you have power? In any case, check the positive power for 12v, if that checks out, turn on your stereo and test the remote line for power, 12 volt as well. If all that is good, be sure you have a solid ground (not a likely problem, but worth checking to be sure), otherwise the amp is fragged. Either get it fixed or just buy a new one.



Okay well I tested them using the dumbass theory, if it sparks it has power. I will go buy a voltmeter this afternoon after school. I would doubt the amp is fragged, but, if that is the case, how would I fix that?


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## captain_shrapnel (Sep 10, 2004)

If there is spark, its probably the remote wire. If the amp is broken, it needs to be sent back to the store/manufacturer to be fixed.


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## TheMadCheshire (Dec 30, 2004)

Even a cheapie from harbor freights is better than the dumbass theory. Good name btw. Fixing the amp is prolly something best left to a shop. I know some people have fixed theirs, but it really depends on whats wrong with your amp. Basically, each amp has its own flaws.


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## pimpride (Mar 28, 2005)

Well I just bought a volt meter about half an hour ago. I tested and my + and - leads are fine. I wasn't sure on how to go about testing the remote wire. I used the - lead as my ground, and then put the positive tester thing on the remote wire. I got .03 volts. If I read the above correctly, it should be somewhere around 12v? If so what do I do about the wire, just replace it?


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## pimpride (Mar 28, 2005)

Sorry for the repetitive post, just thought it deserved a new one.

Update:

I got the amp on YAY! I ran a new wire to a +12v supply that turns on when the car does so the amp doesn't kill my battery.

I am still having problems, I have everything hooked up, but the subs aren't woofing. The amp is lit up and everything, but not a peep from the subs. What could do this?

Do I have to adjust the gain before I hear any sound? Right now it is turned all the way down. I believe I have them wired right, both go to their own speaker terminal. Two 4ohms= One 2ohm right?


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## captain_shrapnel (Sep 10, 2004)

pimpride said:


> Sorry for the repetitive post, just thought it deserved a new one.
> 
> Update:
> 
> Do I have to adjust the gain before I hear any sound? Right now it is turned all the way down. I believe I have them wired right, both go to their own speaker terminal. Two 4ohms= One 2ohm right?


Start with the volume on HU about 3/4 up and the amp gains all the way down. Turn up the amp gains till you get to distortion then back them off some. Two 4 ohms= one 2 ohm load, if they are wired in parallel (not series). That would be + speaker wire going to both +'s of the 2 speakers and the - speaker going to the 2 subs -'s terminals. Basically fork the wires between the amp and the 2 speakers, kinda like a y-adaptor would. This assumes your amp is something that can be bridged (or monoblock) to a 2 ohm load, and the speakers are single voice coils.


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## pimpride (Mar 28, 2005)

Wouldn't I be able to hear the subs even with the gain all the way down? Right now they don't even budge. I have them wired so that each has their own plug in on the amp.
Spkr2|Spkr1
-....+|-....+

That is what the amp sub plug ins look like, and that is how I have them hooked up. Is that right?


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## captain_shrapnel (Sep 10, 2004)

Ideally, no you shouldn't hear anything with the gain down. Here, maybe this will help with the wiring... http://www.bcae1.com/spkrmlti.htm


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## pimpride (Mar 28, 2005)

Okay well I will try the gain again, how do I know what is 3/4 up?

Hear is my setup-










Does that seem right?

Edit: I tried the gain again, on volume 20, no response from the subs. My amp also has a Bass Boost with settings 0, 6, and 12. It is on 0 right now. The amp is rated 160watts rms, but scored 202watts rms. So that should give me 101watts rms per sub right? The subs can handle 150rms. I really want to get these working.


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## captain_shrapnel (Sep 10, 2004)

a rough guess will do. The idea is to get it fairly loud, but not distorting from the HU.


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## pimpride (Mar 28, 2005)

I edited above ^^^.

And by head unit you mean the actual CD player right?


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## captain_shrapnel (Sep 10, 2004)

you have the RCA cables hooked up, right?


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## pimpride (Mar 28, 2005)

Yes I do. The subs should work, they are brand new.

I should also mention that the subwoofer isn't enclosed, but it isn't neccessarily Infinate Bass. It looks more like a table with two holes in it . It's only temporary, but I doubt this has anything to do with it.


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## captain_shrapnel (Sep 10, 2004)

ok, so the rca cables are attached, the gain is opened, the volume on the hu is up, there is power going to the amp, hmmmm....

ok, with the amp on, set the voltmeter to read an AC voltage signal. Put in a cd and turn the volume up some. Test the speaker outputs, the voltage will change alot, but thats ok. Be sure to ground on the speaker terminal -, NOT chassis ground. Your trying to trace the problem, if you get signal on both outputs then its prolly the subs. No signal and its the amp or before it in the chain. If you get no signal at the amp, check for a signal from the rcas going into the amp.


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## captain_shrapnel (Sep 10, 2004)

pimpride said:


> \
> I should also mention that the subwoofer isn't enclosed, but it isn't neccessarily Infinate Bass. It looks more like a table with two holes in it . It's only temporary, but I doubt this has anything to do with it.


woah, stop the boat. are your subs moving, or not making noise? subs out of a box are pretty quiet, you HAVE to have a properly built box to make the subs do anything.


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## pimpride (Mar 28, 2005)

I tested the subwoofer outputs on the amp, did you mean to test the actual speaker outputs on the amp? Anyways I didn't get any readings from the amp outputs I tester. I got a .1 reading on and off for about 10 seconds and then just a flat 0.

I think this means my amp is messed up, but I can still test the RCA inputs. How would I do that? The same way as I tested the subwoofer outputs?


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## pimpride (Mar 28, 2005)

captain_shrapnel said:


> woah, stop the boat. are your subs moving, or not making noise? subs out of a box are pretty quiet, you HAVE to have a properly built box to make the subs do anything.


My subs are doing neither!


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## captain_shrapnel (Sep 10, 2004)

ok, test the rcas too. if you get something there, your amp is the problem.


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## pimpride (Mar 28, 2005)

Test them the same way then? With the Ground as my RCA White wire and my Red RCA wire as my Positive on AC?



EDIT: Okay well I tested it both ways, with my Red as +, and my White as Ground, and vice-versa. I got nothing except that .1 for a few seconds. Whew, so maybe my amp is okay?

Hopefully so. I can't really do much more tonight, it is pretty dark out.


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## captain_shrapnel (Sep 10, 2004)

no, pin in the center is positive, sleeve is negative.


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## pimpride (Mar 28, 2005)

Okay well I can check that. 

Edit: No voltage on either RCA cable, but that is using AC. Am I supposed to be measuring DC? This is a good sign... Even if I have to replace the CD player it would be cheaper than replacing my amp lol. Hopefully it is just the wires, either they got cut or came unplugged.

Thank you so much for your help so far!


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## captain_shrapnel (Sep 10, 2004)

No, you still will be checking ac voltage at the rca cables. Audio signals are always ac. Ok, if you have no signal at the rca's, check the output of the HU for signal. Is the rca connected? Is there an internal setting to activate them? ARe there level adjustments for the rca? This is the next step to look at.


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## pimpride (Mar 28, 2005)

Okay when I get home in 3 hours (In the school library), I will check those things. If everything is hooked up and stuff, I'll look in my HU Manual for instructions if it has them...


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## pimpride (Mar 28, 2005)

Well it turns out all of this was for 3 unplugged wires. I guess my brother unplugged the RCA's and the Remote wire. Subs and Amp work fine now, except subs sound like shit without an enclosed box.

Thanks for your help Captain Shrapnel. I learned stuff so it wasn't a complete waste.


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## wes (Apr 30, 2002)

pimpride said:


> Well it turns out all of this was for 3 unplugged wires. I guess my brother unplugged the RCA's and the Remote wire. Subs and Amp work fine now, except subs sound like shit without an enclosed box.
> 
> Thanks for your help Captain Shrapnel. I learned stuff so it wasn't a complete waste.


Where did he unplug them from the HU or the amp? Either way I would think you would have noticed that given that you were messing around with stuff. 

Get a box ASAP!


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## pimpride (Mar 28, 2005)

He unplugged them from the HU, I would have seen them unplugged from the amp .

I will get a box. I actually just took all of it out because my car isn't working now. It's blowing billows of smoke out of the exhaust, it is so bad when I drove down the block I couldn't see anything behind me.


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## captain_shrapnel (Sep 10, 2004)

pimpride said:


> Thanks for your help Captain Shrapnel. I learned stuff so it wasn't a complete waste.


Hey, no problem. Were all here to learn something :thumbup:


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