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any electronics wizards out there willing to help with an amplifier problem?

ForOffRoadDriving

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I installed my system about a year ago and everything has worked just fine up until about a week ago. The problem im experiencing is that my amp keeps turning on and off whenever it feels like it (when the igniton and radio are turned on of course) and its driving me crazy! i am running 3 mtx roadthunder amps, 2 of them are the RT202 model which are powering my subs (2- 8" jl 8W1V2's; 1 amp per sub), and 1 RTP202 model which powers my front and rear speakers. I have them daisy chained together starting with the rt202s and ending with the rtp202; when the rtp stops putting out the led indicator goes out also but the rt amps are still lit and keep playing the bass line without skipping a beat. I used my voltmeter and tested the positive terminal (13.9v present when running), the ground terminal to grounding stud (0 ohms of resistance), and the remote wire terminal (10.8v present, same as the other 2 amps measured) but the amp will not turn on. I removed it from the vehicle and using a battery jump box "bench tested" it to make sure it would turn on and it does. I left it hooked up for 20 min and it never turned off so i put it back in the truck and now ive got nothing once again. Its frustrating because when it turns on it produces clean sound with no interference but then without warning it turns off and im left with just the bass line again. Is it possible that something inside could be causing this intermittent failure and if so what do you think it is? ive already disassembled it and inspected the capacitors for bulging and loose solder joints on the circuit board but i found nothing out of the ordinary which makes this all even more frustrating. Ill post a pic of my setup so that you guys can easily visualize what ive got going on back there.




Heres a link to the build thread of my system: http://www.therangerstation.com/forums/showthread.php?t=74314
Page 8 has the majority of relevant pictures on it
 
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shane96ranger

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Get your ohm meter and measure the resistance for each pair of wires. It sounds like an ohm overload possibly. Might be a touching wire somewhere or even a blown speaker.
 

ForOffRoadDriving

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youre talking the pairs that go to the speakers correct? check the resistace from the - side, through the speakers coil, and out the positive kind of like checking the resistance of an ignition coil or fuel injector? i honestly didnt think id get a reply this quick, thanks! ill do some checking tomorrow when i get out of work. it just seems weird that the LED goes out and then comes back on, seems like if it was a speaker wire short or a hot to ground short that it would pop the fuse right?
 

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No it shouldn't pop fuses, it'll just turn on or go into protect mode. I'd also run a pairs of wires for each +/- on the subs
 

ForOffRoadDriving

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No it shouldn't pop fuses, it'll just turn on or go into protect mode. I'd also run a pairs of wires for each +/- on the subs
are you saying disconnect the door speakers from the middle amp and hook up 1 sub per channel since i know the subs work fine, and then see if i have the turning off problem still?
 

shane96ranger

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Disconnect the speakers from your amp and measure the resistance on the left, then the right.

It is going into protect mode either because of heat, or a overload from a short. This will determine which.
 
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407Link

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No I was saying for the subs it you run a pair of wires on the + and a pair on the - (speaker wires have 2 wires, tiwst them together and put on + side then repeat for the other) from the amp to the sub(should sound better) but for the door speakers unhook the speakers from the amp and turn on, if it stays on its a short in the speaker wires or speaker
 

ForOffRoadDriving

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well i disconnected the speaker wires and turned on the stereo but the amp still stayed off, so i smacked it and it turned on, so then i took a video of it until it went out but i need to upload it to you tube and post it up.
 

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Are you running all 3 amps off the one remote lead off your head unit? You could be drawing too much off your remote, causing a voltage drop that is too much, causing the one amp not to trigger on...
You should see closer to 12v off your trigger... Try hooking up a relay to your remote lead to trigger a 12v signal...

If that doesnt work, then maybe the amps turn on circuit is gone kapput. :dunno:
 

ForOffRoadDriving

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well i got the amp fixed, it ended up being a cold soldered joint that came loose, so im thinking it must have gotten hot enough at one point to go into protect mode, and thats likely when the solder liquified and thinned out around the connection. i would have never figured it out on my own, but luckily one of my acquaintances through work saw me fiddling with it yesterday and he just so happens to be an electronics wizard, so he suggested using a heat gun to evenly heat the circuit board and then let it cool for 20min and then test it for power. that smart ass was right and now im back in business!



after the heat gun treatment it turns on and stays on!


i did have a plan B in place so that i wouldnt have to drive to the dunes with no tunes, but i wasnt crazy about it. heres the amp i was going to borrow from my buddy, its a lightning audio ff150.2 that has the same specs at 2ohms as my MTX so it would have been a good temporary replacement, but im happy to have my original set up back in place and bumpin.


 
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shane96ranger

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Awesome! I'm glad you got it working again!
 

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