Amp problems - cuts in and out.

[Plutoman 10+ year member]

Alright. This post is for my friend's 300ZX, he's running a single Jensen amp. He got it cheaply off a friend when his friend stopped using it, he doesn't have a lot of money, so getting a new amp is out. If he can't get it working, then he's just running it off the HU.

Situation - 600W Jensen amp - supposedly rated for 150 watts RMS at 2 ohms times four channels. He's running infinity coaxials that are 2 ohm speakers, gains at minimum, because they're rated for 60 watts RMS.

As he's playing, the amp will cut in and out. Usually on bass hits, but not always. You can tell when the amp light flicks on and off. Sometimes it just seems like it's skipping on a cd, but then at other times it just cuts completely off for a few minutes.

He's got a nice JVC HU, which is pretty new.

Suggestions? His battery is pretty old - I wondered if it was that. The car's an '86, so the alternator could be going out. I'm wondering about power draw. It's a small amp, though, so I'm not sure. Trying to figure out the cheapest solutions here.

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[lantz 10+ year member]

first thing to do is definately check the ground wire where it goes to the chassis.make sure theres no paint under the ring terminal.i know a shitty ground connection does this.

 

[Plutoman 10+ year member]

first thing to do is definately check the ground wire where it goes to the chassis.make sure theres no paint under the ring terminal.i know a shitty ground connection does this.

Checked that, though I'll recheck that. I don't think that's it, though I guess it's a possibility. When checking it, I got a full good connection with the DMM.

 

[thegreatestpenn 5,000+ posts]

is the HPF on? it shouldn't be affected by low notes if the high pass filter is on. The amp is probably not a big fan of 2ohm loads. is it covered up? maybe its not getting enough circulation

 

[Fach 10+ year member]

haha happened to my car also the other day, found out it was the headunit skipping the cds when the bass gets too high. I have a 2005 jvc head unit, I guess the laser is just burning out.

 

[thegreatestpenn 5,000+ posts]

same thing is happening with my jvc HU //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif. cd's have trouble reading from time to time and sound scratchy. good thing the USB connection has no problems //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Fach 10+ year member]

yeah, im feeding about 1250rms and when I turn the volume up to where the bass is significantly loud itll cut out sometimes, like its "skipping" sometimes it doesn't but its starting to do it more and more, so there's a good chance it could be your headunit.

 

[thegreatestpenn 5,000+ posts]

it doesn't matter if its bass or not, the laser just seems to lose its way at times with mine. but with ipod hookup, usb, and aux in i don't really need to use cd's again

 

[Fach 10+ year member]

The way I can tell its the problem is because when I turn the radio on, which is usually lower then cds, but turn up the bass as loud as it will go and put the volume up real loud, it doesn't skip when the bass hits.

 

[Plutoman 10+ year member]

is the HPF on? it shouldn't be affected by low notes if the high pass filter is on. The amp is probably not a big fan of 2ohm loads. is it covered up? maybe its not getting enough circulation

HPF is set at 80hz, but it's still cutting out on lower notes, they're toned down, but not completely filtered, since it's a slope. It's mostly those lower notes though that make it cut out. It could be the 2 ohm load, it's kinda funny though, when he hits the amp, it turns back on sometimes. Makes me wonder if something's loose in it. It's a Jensen, so, ya know. -.-

He plugs in his Zune, with the same problem. So it's not the laser. I'm thinking it's something with the amp, or possibly an RCA connection. The HU is only about a year and a half old. I can get model numbers for everything tomorrow.

 

[thegreatestpenn 5,000+ posts]

could be something loose on the amp's board. that happens sometimes

 

[lantz 10+ year member]

use a DMM and check the voltage at the amp when its playing to see if its dropping at too low a voltage.also,make sure the rca's arent loose where they go into the amp.is the amp mounted on the sub enclosure?

 

[Disco Nate 10+ year member]

First thing

1. how many speakers are hooked up per channel?

2. Is it bridged? If so usally when a amp is 2ohms stereo it going to be 4ohms bridged just something to think about.

 

[Plutoman 10+ year member]

use a DMM and check the voltage at the amp when its playing to see if its dropping at too low a voltage.also,make sure the rca's arent loose where they go into the amp.is the amp mounted on the sub enclosure?

No subs - just speakers. I'll check that tomorrow, it's midnight tonight. My friend would probably find it odd to see me checking out his car at midnight.

It's one speaker per channel, each speaker is two ohms, four speakers on all four channels.

I'll open it up tomorrow, too, to check it out.