4 Channel Amp Spends Majority of Time in Protection Mode.

[GMFreak38]

I just finished installing a car audio system in my Buick. I have an Infinity 475a 4 channel amp, and a JL Audio a1800 mono sub amp. I used 0/1 gauge main power wire connected to a distribution block that splits the power line into two 4 gauge wires. The two 4 gauge wires then run to the two amps. I also have the grounds connected the same way.

My problem lies with the Infinity amp (the JL Audio amp comes on fine). The infinity amp appears to come online just fine, but the protection light remains lit for a good chunk of the time. Randomly it'll switch from protection mode to normal mode for a split second before returning to protection mode. When I had it connected to speakers, it would play a short part of the audio when coming out of protection mode. To rule out any speaker shorts or problems with the RCA inputs, I disconnected everything except the remote turn on lead, 12 volt power, and ground connections. With just these connections remaining the amp still does the same thing.

Using the same distribution blocks and grounding points the JL Audio amp appears to be running just fine. I don't have a sub connected to it yet, but the power light is on and the protection light is off, so at the least it's doing better than the infinity amp. I also checked the voltage running to the amps using a voltmeter connected to the terminals on the amps. When the car is off it's reading 12.28 volts, and when on it reads 14.32 volts. The remote turn on lead is around 12.5 volts. All the voltages seem to be within range.

Does anyone have any more pointers for troubleshooting this issue? I'm starting to believe that it's a defective amp, but I hope it's not. Hopefully you guys here can help me out with this. Thanks in advance.

[pre98zetec]

sounds like a loose wire/bad ground.

[GMFreak38]

Originally Posted by pre98zetec

sounds like a loose wire/bad ground.

I have it grounded to the sheet metal on the bottom of the trunk. That's not good enough is it? But then it begs the question...why does the JL Audio amp seem to work just fine using the same grounding spot? Thanks for the quick reply.

[pre98zetec]

Really a tricky question. I had 2 amps the same way. The component amp was fine but the sub amp would go into protection if you tried to turn it up.

Are the wires tight in the infinity amp? Does it ever work? you said it comes on, does that mean it plays, or just comes out of protection? Try running it off the wires the JL amp is.

Just because the JL amp comes on, doesn't mean it can't be a bad ground. That amp has no load on it. It could go into protection with a load

[GMFreak38]

Originally Posted by pre98zetec

Really a tricky question. I had 2 amps the same way. The component amp was fine but the sub amp would go into protection if you tried to turn it up.

Are the wires tight in the infinity amp? Does it ever work? you said it comes on, does that mean it plays, or just comes out of protection? Try running it off the wires the JL amp is.

Just because the JL amp comes on, doesn't mean it can't be a bad ground. That amp has no load on it. It could go into protection with a load

I've got all the speaker wires on the infinity amp disconnected, along with the RCA inputs. The only wires connected now are the 12V, ground and remote turn on. The wires seem to be snug in the terminals. I'm attempting to ground it directly to the frame of the vehicle right now (which is essentially two inches from where I originally had the ground in the sheet metal anyway.

The amp has blue lights that come on for decoration. Those come on. A few seconds later the protection LED will light up. Occasionally it will come out of protection and the green power LED will come on. This occurs for maybe 1-2 seconds. Before I disconnected the speaker wires, sound would play when the green LED power light was on, but I have since disconnected the speaker wires in order to narrow down the problem.

[pre98zetec]

I would try a new ground then report back.

[GMFreak38]

Originally Posted by pre98zetec

I would try a new ground then report back.

Just finished changing the grounding location. It is now directly grounded to the frame. It still does the same thing. The protection light will stay on for the majority of the time followed by random lightings of the power light (which is normal operation). I should mention the lights dim when the amp switches to the "normal operation" mode temporarily before switching back to protection mode. I don't know if that means anything. Like I said though, the JL Audio amp is just fine. I really hope it's not defective.

Is there a way I could test the amp?

[pre98zetec]

You could get a spare car battery, hook the wires up to it just hook the remote wire directly to the hot wire so it will always be on and see if its turns on that way.

[GMFreak38]

Originally Posted by pre98zetec

You could get a spare car battery, hook the wires up to it just hook the remote wire directly to the hot wire so it will always be on and see if its turns on that way.

I'll have to try that later on. Does the symptoms of the random spurts of normal operation usually indicate an amp problem or something else?

[PaulD]

the only things that send an amp into protect mode is 1) overheating 2) DC offset in output 3) short in speaker wires or defective output IC's.

[GMFreak38]

Originally Posted by PaulD

the only things that send an amp into protect mode is 1) overheating 2) DC offset in output 3) short in speaker wires or defective output IC's.

What exactly is DC offset in output and defective output IC's? is it something that could be caused by improperly connected power cables? such as power wires that have a few exposed strands? I'm just grasping at straws here to see if it's anything i can do to fix the problem or if 'm just going to have to wait for a replacement amp to arrive from the dealer i bought it from.

I'm currently at work right now typing this on my pda, but hopefully later today i can try and do some more troubleshooting. It's really frustrating. I spent a good chunk of three days installing everything and now this one thing is preventing me from enjoying it.

[PaulD]

dc offset is where a steady dc current is getting into the speaker output .... BAD for speakers. instead of IC, I should of said output transistor. If the protect light stays on even when no speakers are attached, you usually have major problems.

Note for situation #3 - wiring in too low of an impedance is the same as a short as far as the protection circuitry sees it.

[GMFreak38]

Originally Posted by PaulD

dc offset is where a steady dc current is getting into the speaker output .... BAD for speakers. instead of IC, I should of said output transistor. If the protect light stays on even when no speakers are attached, you usually have major problems.

Note for situation #3 - wiring in too low of an impedance is the same as a short as far as the protection circuitry sees it.

That basically answers all my questions. You saying that if the protect light stays on with no speakers connected combined with the fact that the other amp works just fine leads me to be 99.9% positive that the amp is indeed defective.

I've emailed the seller, hopefully I'll hear back from him shortly. I bought it on ebay, but the guy is an audio dealer, and has great feedback along with a 6 month exchange policy, so hopefully by the end of this week I'll be up and running again. Thanks for the help with the troubleshooting. Too bad it's a bad amp and not a simple (comparably speaking) issue to fix.