JL 300/4 with Low Ohms Light On

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craigs2k

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Joined: December 07, 2008

Location: Montana, United States

Posted: December 07, 2008 at 8:57 PM / IP Logged

Just wired everything up, all were wired correctly. Triple checked. Brand new rear speakers, brand new RCA's, fairly new front speakers etc etc... The amp currently has no speaker wires hooked up, no RCA's hooked up. Only power, ground and remote. With the three wires hooked up the amp's Low Ohms light turns on immediatly and stays on. what could cause this? When the RCA's and speakers were wired up, it played music but heated up fairly quickly. I bought it used, heard it work, but didn't know much about about the low ohms light to check. Anyone had this experience and know what it could be? any help is appreciated, and I would like to figure it out myself because its not under warranty.

soundnsecurity

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Posted: December 07, 2008 at 9:18 PM / IP Logged

maybe an internal short

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craigs2k

Member - Posts: 8

Joined: December 07, 2008

Location: Montana, United States

Posted: December 07, 2008 at 9:23 PM / IP Logged

wouldnt the amp not work completly then?

xplorin16

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Joined: November 08, 2008

Location: Georgia, United States

Posted: December 07, 2008 at 9:41 PM / IP Logged

JL's are excellent amps, i have the 300/4 also. One of the only downfalls of Jl amps are that they do not have on board fuses. There fore if you were to accidently short the outputs of the amps it could cause internal damge, that could only be fixed by jl or a electronic repair specialist.

I would contact JL and see about a repair.

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craigs2k

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Joined: December 07, 2008

Location: Montana, United States

Posted: December 07, 2008 at 9:42 PM / IP Logged

Looks like I get to crack her open tomorrow since I dont have a warranty, yay

i am an idiot

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Joined: September 21, 2006

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Posted: December 07, 2008 at 10:02 PM / IP Logged

If all 4 channels played and had no distortion on any channel, there is probably no shorted outputs in the amp. There is a biasing adjustment on each channel, if someone tampered with these adjustments, it is likely that this is your problem. Do not play it until you do this. Unhook the amp and set it upside down on a flat surface. Remove the 3 phillips screws from the bottom cover, and remove the cover. Heat sink fins away from you, There are some vertical circuit boards on the left hand side of the amp. Between these boards mounted to the main circuit board, there are 4 Blue Potentiometers with yellow center pieces. The yellow piece is the piece that needs to be turned. It will require a #0 phillips screwdriver. That is a small "Jeweler's Screwdriver" Locate all 4 of the pots and try to turn them gently, in the clockwise direction, If they do not turn, this is definitely your problem. Turn them all of the way down. These pots at full counter clockwise position will cause NO DAMAGE to the amp. Fully clockwise they WILL DAMAGE the amp. Hence the heat you are dealing with. If you have access to a 10 amp capable amp meter, I can teil you how to properly adjust the pots. Till then turn them full counter clockwise and hook it back up, notice if the heat problem has gone away. It is very common to see this in an amp, some IDIOT opens it up and decides that the pot is a magic power limiter that the manufacturer did not want you to find. Their first instinct is to turn it all the way up.

craigs2k

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Joined: December 07, 2008

Location: Montana, United States

Posted: December 07, 2008 at 10:12 PM / IP Logged

do you think that would cause the light low ohms protection light to come on though? I am definatly calling JL tomorrow in hopes of getting some sort of help. I have read that many people have the same problem... but I will try what you are talking about tomorrow thanks alot!

craigs2k

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Joined: December 07, 2008

Location: Montana, United States

Posted: December 08, 2008 at 8:38 AM / IP Logged

fun phone call with JL.

Me: I have a 300/4 and the low ohms light is on with just power, ground and remote wire hooked up, what could cause that?

JL tech: Your amp is defective

Me: Obviously, but what could cause that?

JL tech: You have to send the amp in to have it reparied for 120$.

Me: I don't want to send it in to have it repaired if it is somthing simple, the amp still works, the light is just on.

JL tech: the parts are very expensive, you must send it in for repairs.

needless to say, they are no help at all... I mean, if the amp still works but the low ohms light is on, something causes that to happen. Just wonder what.

craigs2k

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Joined: December 07, 2008

Location: Montana, United States

Posted: December 08, 2008 at 9:57 AM / IP Logged

I just hooked the amp up at my lab at work and the low ohms light did not come on. I lowered the voltage to below 10 and the amp cut off, which it should, so protection is working. I guess I will re check all my wiring.

DYohn

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Posted: December 08, 2008 at 12:15 PM / IP Logged

If you have the amp installed properly but have no speakers connected to it and get a "low ohms" light, the proper reply from JL Tech support is "send it in." If on the other hand you powered it on a test bench and did not get the same results, then there is most likely something wrong with your installation.

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