SMD electrolytic capacitors 10uf 25v

Discussion in 'General Electronics Chat' started by imraneesa, Apr 28, 2016.

  1. imraneesa

    Thread Starter Member

    Dec 18, 2014

    I got few 10uf 25v smd electrolytic capacitors on this pcb (audio car amplifier). the ESR is of all the capacitors are from 3.5 to 7ohms. but as i know the esr for 10uf 25v should be 1.5ohms range.

    it had blown outputs and i have changed them all. earlier it was going into protect mode. but after changing the outputs and some bad resistors the amplifier start to come on and play. but when i increase the volume it is going into protect mode.

    then when i checked these capacitors i am in doubt. so kindly show some light on this. Thanking you in advance.

  2. Tonyr1084

    Active Member

    Sep 24, 2015
    Do you realize a capacitor is basically an open circuit? Well, not exactly, but a perfect capacitor (in theory) will have infinite resistance.

    You can use an ohm meter to determine if a capacitor is shorted, but that's not the best way. The ohm meter sends out a very tiny current and reads the voltage drop across a resistor and determines the resistance quite accurately. A capacitor does not conduct current - it stores it and discharges it back to the circuit (basically). When you test a capacitor with an ohm meter the longer you leave the leads on the cap the higher the resistance reading you'll get because the capacitor is charging up.

    I too had a recent amplifier problem. The main 7 amp fuse blew. When I replaced it the new one blew immediately. Upon opening the unit I found an 8 amp fuse on board had also blown. Suspecting the capacitors I did an ohms check. I was looking for a shorted capacitor. My caps appeared to be healthy based on the test. So I disconnected everything from the power (except the Bridge Rectifier). When I put a new fuse in - it blew immediately. So I took the BR out of the circuit and with another fuse I determined the problem was IN the BR. checking for shorts I found one leg was shorted. Replaced the BR and problem solved.

    I also tested the output transistors, all of which appeared good using the ohms test. Nothing shorted. As to why your circuit is going into protect mode - I can only guess that something in the circuit is drawing too much current. Perhaps if you can isolate certain sections it may help you narrow down where to look. Eventually you'll discover the culprit.

    Good luck with your troubleshooting.