Troubleshooting Capacitors on PCB

Thread Starter

swen

Joined Aug 1, 2014
46
Hi, I'm trying to troubleshoot a Bose Wave unit that won't turn on. These units are notorious for surface-mount capacitors (SMCs) that go bad, and there are many YouTube videos of successful repairs by replacing one or some the capacitors.
My question: I found continuity between the negative side of all the SMCs on the PCB and a common ground on the PCB, except for one SMC. I replaced that SMC. Now an SMC next to the one I replaced is showing no ground continuity. Any idea what is going on? Thank you for any ideas. Tracing the common ground on the board is quite difficult.
 

dl324

Joined Mar 30, 2015
16,988
I have no idea why you're seeing the symptom you describe, but your troubleshooting technique seems to be the "shotgun method" (i.e. not methodical).

If you suspect a capacitor, or any other component, is preventing the unit from turning on, the logical thing to do is to verify that power is good. Since you say that capacitors are the usual cause, it's likely to be one across the power rails that is shorted. In that case, you can try to find the one with the lowest voltage across it while also checking for hot spots around the voltage regulator/power input.

The HP 547A Current Tracer was designed to facilitate troubleshooting problems like this (shorts/stuck-at).
 

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