Is some cases a fuse will open up fast enough when there is a surge so that other components aren’t damaged. If this is case, replacing fuse with one of same type and rating restores operation. Unfortunately, a high probability exists that if a fuse blew, something in circuit it was protecting shorted out. In this case, a replacement fuse blows right away. The blown fuse can easily be replaced by a new one, after overload has been eliminated when come into replacement. Use only same current and voltage ratings as original. The common type and current rating of a fuse in a monitor are slow blow 2A to 5A. When you buy replacement fuses, get several – you can easily use all of them while you’re troubleshooting an elusive problem.

Testing Fuses

Turn power off and remove fuse from circuit to check with a multimeter set to lowest ohms range. Connect probes to both end of fuse. You may check fuse while it still in circuit. A good fuse should showed continuity or read 0 ohm. A blown fuse is open which reads infinity on meter.

(b) Frequency Counter Frequency Counter can be use to check frequency of crystal. The reading must be taken when equipment power is switch “on”. Place probe of frequency counter to crystal pin and read measurement. Be sure that your frequency counter meter has range that is higher than crystal frequency you are measuring.

(c) Crystal Checker With this method, usually crystal is placed in feedback network of a transistor oscillator. If it oscillates and LED is lighten up, this mean that crystal is working. If crystal doesn’t work, LED stays off. Instead of using LED, some other crystal checker uses a panel meter to indicate if crystal is working or not.