Jl Audio 300/4 Troubleshooting Tip - diyAudio
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Old 26th May 2011, 03:30 AM   #1
kds9591 is offline kds9591  United States
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Default Jl Audio 300/4 Troubleshooting Tip

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.
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Old 26th May 2011, 11:51 AM   #2
ppia600 is offline ppia600  United States
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Good find
Don't worry... you can always turn the gain down!
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Old 26th May 2011, 01:30 PM   #3
Boofers is offline Boofers  Canada
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Interesting, thanks for sharing.
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Old 31st May 2011, 01:42 PM   #4
amptech is offline amptech  Scotland
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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..
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