Jl Audio 300/4 Troubleshooting Tip

kds9591 · 26th May 2011, 03:30 AM

Worked on 2 of these JL Audio 300/4 4 channel amps last week with similar problems on the driver boards. ( On these boards the component #'s are not silk screened on the PCB.)

The first amp had a very low output on one channel. The problem was found to be a very, very fine hairline crack in the solder joint for the upper one of the 2 47K ohm SMD resisters on the board.

The other amp had no output on one channel and the bias current was not adjustable. The problem was found to be the lower 47K ohm SMD resister- the plating had separated from the resister. This was NOT visible even under high magnification.

ppia600 · 26th May 2011, 11:51 AM

Good find

Boofers · 26th May 2011, 01:30 PM

Interesting, thanks for sharing.

amptech · 31st May 2011, 01:42 PM

Hello there, I've seen many car amps over the years from burnt pcb's etc..the last one came to me rattling and not powering up due to being bolted to the sub box this is a no no. I would agree there circuit board cracks will make the unit cut in and out...

keep amp away from the bass box well not bolted to it any...lol

even easer this chap would to use his amp in the house so I rigged him up a 750w atx power supply unit to run it on..

26th May 2011, 11:51 AM	#2
ppia600 diyAudio Member Join Date: Jun 2007 Location: Louis y ana	Good find __________________ Don't worry... you can always turn the gain down!

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26th May 2011, 01:30 PM	#3
Boofers diyAudio Member Join Date: Oct 2008 Location: Ontario Blog Entries: 1	Interesting, thanks for sharing.

31st May 2011, 01:42 PM	#4
amptech diyAudio Member Join Date: Jan 2009 Location: Glasgow	Hello there, I've seen many car amps over the years from burnt pcb's etc..the last one came to me rattling and not powering up due to being bolted to the sub box this is a no no. I would agree there circuit board cracks will make the unit cut in and out... keep amp away from the bass box well not bolted to it any...lol even easer this chap would to use his amp in the house so I rigged him up a 750w atx power supply unit to run it on..