Looking At The Sleeve Of Electrolytic Capacitor
In certain electronic problem one would easy to locate the fault because you could see that the sleeve of the electrolytic capacitor had shrinked! For your information not all e-caps that have a shrink sleeve must have problem. Assuming if one out of 10 e-caps in one board had shrink then you can suspect that e-cap.
Sometimes the e-cap that had a shrinked sleeve could be test ok but fail when under load. The common problem it could cause was intermittent. If you come across such e-cap the best is to direct replace it and retest the equipment again.