i200yrs
Full Member level 2
Hello all...I am working in industry and recently I found one of my controller assembly from the machine cannot power up. So i removed this certain controller and did a basic troubleshooting. This controller can be power-up by 110Vac and it consist of 1 back-plane pcb with 5 pcb modules plug-in on it. What i did was I removed all 5 pcb modules at a time and power-up. But still cannot power-up even I already removed all the 5 pcb modules. What's left is the backplane pcb. I noticed that the backplane have 8 capacitors soldered on it. So i decided to removed all caps and power-up...so it CAN POWER-UP already. Then right away i measured all caps and found all 8 have high ESR up to 100ohm. I compared with the good one which only have <1ohm...(caps specs are 100uF, 25V)... I am happy in that moment I confirmed it was the capacitors were faulty. However, when I soldered back the original high ESR caps it can also power up. Then this makes me confuse....Hope some experts can explain to me how the high ESR caps can cause no power, but when you removed and soldered it back it can power up again. Thanks in advance.