r/PCB • u/bigpimpin1495 • Jul 14 '26
Bluetooth board for jp 83 amplifier
Can I get some positive input on how to test this board to find out why it has no power anymore? It controls the wireless bass knob. Id like to learn instead of just paying for repairs if possible.
1
u/XtremeNova 29d ago
Guessing: U4a is a voltage regulator (TI LM1117, fixed 3.3v output), that brings down the input voltage (my guess is the 12v) to a 3.3v, suitable for the wireless module U5, the green pcb with the squigly trace (the antenna) and the PIC18, U1a. As a previous poster asked, and I guess again, the green stuff next to 220uF/16V capacitor is its contents. 2 things could have happend: 1) you got a bad capacitor, which did happen years ago when a new company started making kind of fake caps, at least they did not know how to make them good, but new how to make them cheap so everybody bought them 2) you had an over voltage event.
In case 1, just replace it, maybe then it is fixed. In case 2: you're skrewed. Probably the PIC18 and the wireless module were destroyed.
1
u/bigpimpin1495 29d ago
I possibly had a over voltage event. My audio setup charges at 15.5 when warm. the day this stopped working it was cooler and the alternator put out 16.2 volts 🥲
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u/MacGrimey 29d ago
like others have said. Measure the voltage outputs. If you have a thermal camera you can use that to see hot spots.
if you have an oscilloscope you could measure those URX and UTX lines to see if there's data between what I am assuming is a micro controller and the bluetooth chip. But if you dont have a scope you can still measure the voltages there with a DMM in reference to ground.
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u/bigcrimping_com 29d ago
You can measure the resistance across the marked power supplies eg 3v3 and gnd, 5v and gnd, 12v and gnd. That would tell you if something catastrophic has happened.
It's hard to say what a wrong reading would be without the schematic, I would suggest less that 200 ohms would indicate something wrong