Repaired a JL Audio 300/4 Ver1 series with very low audio output on all 4 channels. After some troubleshooting and voltage measurements found pin 3 of U600 on the daughter board had no voltage on it. Pin 3 usually measures approx 4VDC. Problem found to be a open trace connecting R612-R615 caused by a corroded via (plated through hole) had no continuity between top and bottom of brd. See picture.
Hope this info is of help to someone.
Hope this info is of help to someone.
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This is a common problem on JL amps. It always seems to happen near the power/ground terminals. Green corrosion in the vias is a sign that there's a problem. There are almost always several that are near opening (either the pad around the via or the via itself). Many times, you need a high-power lighted magnifying glass to see the damaged (but still connected) traces.
THIS is another thread with a few photos showing the type of damage to look for.
THIS is another thread with a few photos showing the type of damage to look for.
I had 7 other corroded open via's I repaired on the same board including 2 under IC U600. I scraped the coating on the foil both sides to expose the copper, used a dental pick to open up the hole a bit and used 30 gauge buss wire to fill the hole. I used liquid flux to provide better flow through for the solder.
Between the Luxo lamp and a eyeloop I was able to see the corroded via's but some that looked good I found with a meter. I'll have to try that # 80 drill bit method you mentioned in the other JL Audio thread next time.
Between the Luxo lamp and a eyeloop I was able to see the corroded via's but some that looked good I found with a meter. I'll have to try that # 80 drill bit method you mentioned in the other JL Audio thread next time.
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