# JL 300/4 Problems any tips?



## Aleksrussian (Jul 8, 2013)

Hey fellow audio heads, I looked through some of the other 300/4 threads and didn't find a satisfying answer in there. 

I have a JL 300/4 powering 4 JL c2 speakers in my car, when I hit some bumps in the road I get crackling and the front speakers cut in and out. I initially thought the speaker wires were loose so I tightened those down and doubled up on the copper. Later I realized when I touch the RCA cable for the front speaker the crackling happens. Before I spend half the day replacing my RCA cable, is there anything you guys can think of that would cause this? The RCA's are brand new and are good quality. The rear speakers seem to be fine.

More info that may be useful.

JL 300/4v1 4 speakers JL c2.
Mid grade RCA.
Amp is used but works otherwise.
No Low ohm light or thermal light.
Green power light is on.
All power connections feel solid.
Speakers started crackling several days after install.

One last question, can this cutting in and out of the speakers damage them?

Any help would be appreciated!


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## Mack (Jul 27, 2007)

Does it happen to both fronts or just one side. If it's one side swap RCA cable from left to right to see if it follows suit.

If it follows it's the cable, if it stays it sounds like the jack on the amp. You can always run a spare set of RCAs from the H/U to the amp without tearing up carpet just for trials.

It it's on the jack, as long as it's not a broken leg, then it seems to be a simple broken/cold solder joint. A simple fix.


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## Aleksrussian (Jul 8, 2013)

Well actually both sides do that when you mess with the RCA's but typically only one side (driver side) makes noise during driving. Also the other side has given me problems too but never simultaneously. 

Thanks for the tip on trying a new RCA from the HU without tearing everything up! Good idea!

I will switch the RCA's around and see if the problem goes to the other side.

Can you explain more by what you mean by the "leg". All my stuff is screwed to the back of the seat so I can't pull the RCA's out without taking stuff apart..

If its not the RCA's what else can it be?

Thanks for the reply


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## Mack (Jul 27, 2007)

By leg I mean the actual part of the RCA input jack (on/in the amp) that is soldered onto the amp's PCB(printed circuit board). If both inputs are giving you fits, then it's likely a bad componant in the amp......hopefully just the jack. 

Something else just hit me, you're running 4 of the same speakers, so you can actually swap front to rear as well. this will further simplify the problem. 

If the rears aren't giving you any problems, then swap the RCA cable front-to-rear. That will let you know if the cable is the problem.


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## Aleksrussian (Jul 8, 2013)

ahh I see I figured thats what you meant, these dang JL Slash amps are a pain to repair..  I hope its not that. I guess if I switch the rears with the fronts the annoying noise will be further away 

So I guess the actual RCA female ports on the amp could be bent or slightly disconnected from the PCB so they go in and out when the bass hits hard enough or the road is bad?

Any "ghetto" easy fixes? like Stick a screwdriver in there type of stuff? lol :laugh:

You've been good help thanks!


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## shawnk (Jan 11, 2010)

This is actually a fairly common problem with the slash amps. They are fantastic amps, but this is a problem I have seen many times. I know exactly what is going on and yes, unfortunately you need to open the amp to fix said problem.

So here's the deal. There are two (2) possible problems that cause this intermitant malfunction that you are describing. 

1st: There is a dedicated circuit board (known often as a daughter board) that sits above the main board. The circuit is completed between the two boards is completed by several "legs" on the daughter board that sit into a receptacle on the main board. I have found that in some cases, the legs no longer fit snug into the receptacle and can cause intermitant connection/disconnection. To rectify this, I like to add a very "VERY" light coating of solder to each of the legs which allows them to seat a little more snug into the receptacle.

2nd: I have also found that the bottom of the duaghter board rests extremely close to some of the components on the main board and can often short out when the amp is jostled. In "most" of the Slash amps I've opened up I've seen that JL placed a thin cardboard-like strip between the bottom of the daughter board and the main board in an attempt to prevent the shorting, but I have found that the material is so thin that it can actually be punctured by the sharp solder points on the bottom of the daughter board and can still short out on occasion. To rectify this, you can simply duplicate what JL did with the thin cardboard strip, only use a slightly thicker non-conductive material to do the job. (I've had good luck with a strip of velcro.... no it doesn't matter which side you use )

Take care of those two problems and you should be good to go  

Hope this helps

Shawn


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## Aleksrussian (Jul 8, 2013)

Yay got it working right!! Thanks for all the tips! I had a double RCA malfunction, what are the chances... Replaced one than had to do it again with a different one! Fortunately that fixed my problem :blush:


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## shawnk (Jan 11, 2010)

Aleksrussian said:


> Yay got it working right!! Thanks for all the tips! I had a double RCA malfunction, what are the chances... Replaced one than had to do it again with a different one! Fortunately that fixed my problem :blush:


Well ignore my post then....lol :laugh:


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## Aleksrussian (Jul 8, 2013)

shawnk said:


> Well ignore my post then....lol :laugh:


No no, I am a Craigslist shopper, maybe one of these days ill get an amp that needs that done, and what you've explained seems to be a common problem, mini lesson greatly appreciated


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## Mack (Jul 27, 2007)

Aleksrussian said:


> No no, I am a Craigslist shopper, maybe one of these days ill get an amp that needs that done, and what you've explained seems to be a common problem, mini lesson greatly appreciated


Sweet! Rock on!


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## TrickyRicky (Apr 5, 2009)

shawnk said:


> Well ignore my post then....lol :laugh:


I notice that on the longer slash amps (such as the size of the 500/1 and bigger) the daughter board starts to separate from the main board, just like you mentioned. What I did what placed a stiff 3/8 fuel vapor line and with the back/bottom cover it will hold the daughter board nice and tightly against the main board. This happen because of gravity, when the amplifier is upside down the daughter board is just holding itself by both ends (and not by much) while the middle will sag a bit or just enough to cause intermitting. 

I know because I had a 500/1 that did that and with the quick mods I did it fixed it and I no longer had that issue (cutting on and off with bumps).


I've also had to replace a few RCA jacks on a couple of JL slash amps as they where seriously damaged. I got pictures, I'll post them here in a few minutes.


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## Aleksrussian (Jul 8, 2013)

TrickyRicky said:


> I notice that on the longer slash amps (such as the size of the 500/1 and bigger) the daughter board starts to separate from the main board, just like you mentioned. What I did what placed a stiff 3/8 fuel vapor line and with the back/bottom cover it will hold the daughter board nice and tightly against the main board. This happen because of gravity, when the amplifier is upside down the daughter board is just holding itself by both ends (and not by much) while the middle will sag a bit or just enough to cause intermitting.
> 
> I know because I had a 500/1 that did that and with the quick mods I did it fixed it and I no longer had that issue (cutting on and off with bumps).
> 
> ...


I would love to see the guts of one of JL slash amps just to see how much of it I understand so If I do need to take it apart one day I should have any idea of what went wrong. 

I got to tell you guys though I'm loving this setup! Most of you would probably laugh about me going JL since they aren't the best value but I feel more confident in a product I am familiar with and a company that has been making excellent products and are known for it. I'm thinking to add some small midrange drivers, anybody know of anything similar to the accuton midrange drivers except not $400 a peice? It will be for the car, any one used the b&g neo 8-s? 

Probably need a new thread for that huh:surprised:


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## TrickyRicky (Apr 5, 2009)

Aleksrussian said:


> I would love to see the guts of one of JL slash amps just to see how much of it I understand so If I do need to take it apart one day I should have any idea of what went wrong.
> 
> I got to tell you guys though I'm loving this setup! *Most of you would probably laugh about me going JL since they aren't the best value *but I feel more confident in a product I am familiar with and a company that has been making excellent products and are known for it. I'm thinking to add some small midrange drivers, anybody know of anything similar to the accuton midrange drivers except not $400 a peice? It will be for the car, any one used the b&g neo 8-s?
> 
> Probably need a new thread for that huh:surprised:


What? Most here know that JL slash are decent amplifiers. No doubt their pcb design is very complex layout, but they are very nice amplifiers. I currently have a JL 500/1 powering a pair of 12's and it does a fantastic job. Its crossover and eq setting are awesome not many amplifiers have its features.


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## Aleksrussian (Jul 8, 2013)

TrickyRicky said:


> What? Most here know that JL slash are decent amplifiers. No doubt their pcb design is very complex layout, but they are very nice amplifiers. I currently have a JL 500/1 powering a pair of 12's and it does a fantastic job. Its crossover and eq setting are awesome *not many amplifiers have its features.[*/QUOTE]
> 
> Yup! thats for sure! I just been laughed out of other forums for going with JL makes me wonder if I'm the idiot or they are haha. My favorite feature of the Slash amps is the power regulation if it says 500 watts on it, it will do that anywhere from 1.5 ohm to 4 ohm. I have a feeling its pushing closer to 600 watts though, seems much louder than my other 500 watt amp.
> 
> I got my 500/1 wired up to 12w7 and it is very good no problems yet.


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## TrickyRicky (Apr 5, 2009)

Aleksrussian said:


> TrickyRicky said:
> 
> 
> > What? Most here know that JL slash are decent amplifiers. No doubt their pcb design is very complex layout, but they are very nice amplifiers. I currently have a JL 500/1 powering a pair of 12's and it does a fantastic job. Its crossover and eq setting are awesome *not many amplifiers have its features.[*/QUOTE]
> ...


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## Aleksrussian (Jul 8, 2013)

TrickyRicky said:


> Aleksrussian said:
> 
> 
> > Trust me its true to its rating. 44.27V is its maximum output voltage at 4ohms (which translates to 500watts rms). Then of course you have to adjust the gain to keep the voltage to a certain level to match the impendence.
> ...


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