Don’t be fooled by e-caps
I believe you have seen lots of bad electrolytic capacitors are due to bulged on top of the cap. The bulged e-caps usually can be found in LCD Monitors, LCD TVs or even Plasma TVs. It is very easy to spot them and usually after replacement the equipment will come back to working condition again. One thing you may not know is that sometimes an e-cap (no bad appearance in the outer body) that’s look good outside have bad ESR and capacitance value. If you did not check on these e-caps and assume that they are fine then you have just made one of the biggest mistakes.
The other day, a customer sent in a 17″ CRT monitor (customer insisted wants to repair it) with the complaint of intermittent display dim and when have display you could see a dark crooked line across the display vertically (very obvious under white background). Initial scanning did not reveal any bad or bulged e-caps. Those e-caps at the secondary side looked very new and no sign of failure. But when tested with ESR meter, I found almost 7 e-caps out of range (high ESR value). With the replacement of the 7 e-caps the monitor was brought to life again with beautiful picture. No more intermittent dim display and no more dark crooked line across the screen.
Don’t be fooled by a good looking e-cap. You just have to test it out. If you missed the bad e-cap the rest of the troubleshooting time will gone to waste.