Got one of these that is a tough dog. Everything is fine, except there are no LEDs, draws no current, its as if it has no remote signal. Matter of fact, thats exactly what it is.
I know the remote circuitry is on the pre-amp PCB. So i swapped another pre-amp PCB from a known good unit in, The amplifier powers up and works fine.
but the original pre-amp PCB does not. So i begin checking transistors around the LM324 circuit. (remote circuit) and am coming up empty. Even checked all the resistors, they are fine.
There is a 5-leg SOT23 transistor that has a Marking N09 B or it might be 60N. Not sure. Cant find any data on this part. Closest thing I found was an Analog Devices watchdog/reset management controller and i know this isnt right. the pinning isnt the same.
The working board has 1.8V between the 22K resistors next to that part. The non-working board has 7.3V there. with 0V on the other side whereas working board has 5V.
I know the remote circuitry is on the pre-amp PCB. So i swapped another pre-amp PCB from a known good unit in, The amplifier powers up and works fine.
but the original pre-amp PCB does not. So i begin checking transistors around the LM324 circuit. (remote circuit) and am coming up empty. Even checked all the resistors, they are fine.
There is a 5-leg SOT23 transistor that has a Marking N09 B or it might be 60N. Not sure. Cant find any data on this part. Closest thing I found was an Analog Devices watchdog/reset management controller and i know this isnt right. the pinning isnt the same.
The working board has 1.8V between the 22K resistors next to that part. The non-working board has 7.3V there. with 0V on the other side whereas working board has 5V.
It might not be a component failure. JL amps often have problems with a lack of plating or corrosion in the via's(plated through holes) causing open traces.
Trying to just eyeball them is not enough as even under magnification they can look good but are not. Check the traces for continuity in the remote circuit and any that you are unsure of where they go (ex:trace goes under a component) check against the known good board you have for comparison.
Trying to just eyeball them is not enough as even under magnification they can look good but are not. Check the traces for continuity in the remote circuit and any that you are unsure of where they go (ex:trace goes under a component) check against the known good board you have for comparison.
Look for any feed-throughs that have a green powdery substance in them. Do not clean the board. The images below show the substance before and after cleaning. The defective feed-throughs are easier to find before you clean the board.
You may need a high-power lighted magnifying glass to see the damage.
You may need a high-power lighted magnifying glass to see the damage.
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So many of these car amp repair threads start out well but end up being cliffhangers with no conclusion.- Status
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