The complexity of the test capacitor
When measuring the capacitance of the capacitor on the Board without preliminary dismantling problems. The capacitor is always included in the circuit and can coexist on the PCB with other circuit elements. Particularly affect the capacitance of the transformer windings, inductor, fuses - they have a small DC resistance.
Therefore, you must ensure that the circuits of the measured capacitor is no influence of such elements. If circuits with capacitor included a transistor or diode, then when measuring it is possible to see the deflection to a certain position and drop to a certain value equal to the resistance of the transitions of the semiconductor. And if there is no short circuit, the capacitor may be defective.
When you touch the probes of the multimeter to the capacitor is supplied a constant current from the tester. The capacitor will charge, and the resistance gradually increase.
On the electronic tester value will grow from negative or positive values to one indicating a resistance that exceeds the measuring range selected by the shift knob. After permutation of the probes of the tester places the capacitor must be recharged, the device needs to act as well.
On the deflection dial of the multimeter by connecting a capacitor and return it to its original position can be seen in a scale the maximum deviation.
If you swap the probes, the meter pointer must deflect to maximum and gradually fall to their original position. After the need to take similar and known-good capacitor and if the pointer of the tester on the control element is deflected more, check the condenser outside.
If the measurement and compliance of the pros and cons on the tester and terminals of the capacitors the instrument will show the resistance, then the condenser is faulty.
Check condenser other devices
There are devices which you can check the capacitors directly on the Board. Such devices operate on low voltages to reduce the risk of disabling other elements.
It is possible to manufacture the attachment to the tester on the schemes published in magazines and on the Internet. But not always it is possible to measure accurately due to the effect of other circuit elements. For example, several parallel capacitors at the end will show the total capacity.
Advice 2 : How to determine the efficiency of the condenser
There are two main types of capacitors faults: open circuit and breakdown. In addition, the breakdown may be partial (then it is a leak), or occur only at a certain voltage). Also a capacitor may lose capacitance or he may increase the equivalent series resistance.
Any check capacitor is fully discharged, both its output should be disconnected from any other circuits. Neglect of this rule in danger of electric shock and equipment damage.
Connect the ohmmeter capacitor (electrolytic is in the right polarity). First, through the device should go current, but after charging it needs to stop. The small capacitors it turns so fast that the ohmmeter does not have time to react. Help penlight batteries, connected in series with the headphones. Such a probe must be connected to the capacitor several times. If the click will be heard only when you first connect, the device is working properly. If the current continues to flow, there is a breakdown, does not occur even if charge is open.
To detect intermittent breakdowns, which manifests itself only at an operating voltage, make the circuit of the voltage source, equal to the condenser, the milliammeter and the load, limiting the current to a safe value. Electrolytic capacitor connect in the correct polarity. Current must first occur, and then rapidly decrease to zero. Turning off voltage, discharge the capacitor.
Leak check the capacitor, charging it up to operating voltage, and then disconnect from the power source. After some time, check the voltage on the capacitor with a voltmeter. Electrolytic capacitor should hold a charge for at least half an hour, and any other - at least a few hours. After checking the discharge component.
The capacity check, perform by using a bridge device. Select such a limit, which by rotating the handle of the bridge the sound disappears. Find the location of the pointer in which the sound disappears completely, and read the capacitance value on the scale. Compare it with the nominal.
To check the equivalent series resistance, use a generator operating at a frequency at which the capacitive resistance can be neglected. The generator must produce a sine wave voltage to the voltmeter and the AC voltmeter worked with the least possible error. Divide the voltmeter readings of the milliammeter (pre-translated in the SI system), and you will receive the equivalent series resistance of the capacitor in ohms. The smaller it is, the better.
Do not touch the chain under tension, as well as the conclusions of the charged capacitor. To discharge use no jumper, as the load limiting discharge current to a safe value.