I have a set of JBL LSR25P speakers in which one had a popping noise about once every 2-3 seconds. A local tech (who only worked on pro equipment) bet without looking it was a bad cap. So I replaced all the caps and the problem persisted. The board has 3 LM3886 amp chips. 2 of them appear to be a push-pull setup and drive the woofer. The other one drives the tweeter. I powered it up and noticed that the LM3886 that ran the tweeter was extremely hot. The other two were room temperature. The datasheet stated that it has thermal overload protection and will shut down at a certain point and then restart. I figured that was what I was hearing. Being a novice I expected the chip was bad. I replaced it and powered up. The new Chinese chip exploded. So now I wonder if the tweeter was shorted and blew the cheap chip while the original could stand it. The tweeter appeared open now and I thought maybe the exploding chip drew enough to burn it out. So I got another chip and left the speakers disconnected. Turned on and the chip didn't blow but it quickly grew extremely hot again. Turned it off quick. I have verified the +-35volt supply at the chips. But I need help. I've attached the schematic and datasheet for the LM3886. Any guidance is appreciated.
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Re: JBL LSR25P amplifier chip overheating
Spray contact cleaner in those hf switches and look to see if you have DC going through those coupling caps between stages. Also if you have a scope look for for oscillation on that hf path -
Re: JBL LSR25P amplifier chip overheating
"The new Chinese chip exploded"
now its anyone's guess without knowing if the new ic is fake or not .Comment
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Re: JBL LSR25P amplifier chip overheating
A clean switch is good but could a dirty one play a role in this problem? So do I need to pull this chip again to do this testing?Originally posted by Devil_rider View PostComment
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