Burning Smell From Electronic Equipment
If the customer complaint that there are burning smell in the electronic equipment (assuming is a Monitor or TV) and the equipment still functioning or the equipment working intermittently, the first thing that you need to do is to check for dry joints in the power side area. Check the AC supply line (connector) especially the pins as dry joints could cause minor spark can creates smell. If it okay then you need to check on the flyback transformer area as this area are also prone to dry joints problem. Check on the horizontal yoke coil area and the flyback pins that connected between the B+ and the HOT collector.
Once you have identified the fault, then use a cleaner (Thinner or any other recommended PCB cleaner) with the help of a small brush to clean the darken area (usually sparking would cause the board to become black in colour). Apply some soldering paste and then solder and the joints will become even better than original and i’m sure the joint will last for a very long time. Just in case if you don’t want the customer to complaint again for the same problem, take some of your time and resolder all the suspected joints, particularly on the joints where high voltage are present like flyback transformer pins, HOT, Yoke coils, switch mode transformer pins and AC input pins.