Switching power supply maintenance experience?
1. If the switching power supply does not start, generally check whether the switching frequency is correct, whether the protection circuit is blocked, whether the voltage feedback circuit and current feedback circuit are normal, and whether the switch tube is broken down;
2. Transformers generate heat or emit a "sizzling" sound, usually due to incorrect switching frequency;
3. The flashing output voltage power indicator light usually indicates a short circuit on the secondary side.
Generally, switch tubes, charging resistors, and rectifier diodes are prone to damage... Therefore, a digital multimeter is usually used for measurement first, and those that are not damaged are tested on power. It would be even better to check if there were burnt areas on the surface
Please consult the maintenance methods for switch power supplies without output. 1. Maintenance methods and steps for switch power supplies without output; (1) Check if there is a 300V DC working voltage at the C-pole of the switch tube, if not; (2) If the voltage at the C-pole of the switch tube is normal, measure the power switch at the moment of startup; (3) If the oscillation circuit is found to be normal, test the power supply+b1 immediately after starting; 1) Pulse width or frequency control circuit (including forced opening by relying on optocoupler conduction; 2) load short circuit (referring to parallel switching power supply, due to series switching power supply; 3) switching power supply causing protection circuit action due to output overvoltage or overcurrent; and grounding at the+b1 end of switching power supply
1. Maintenance methods and steps for switching power supply without output
(1) Check if there is a 300V DC working voltage at the C-pole of the switch tube. If not, check the AC input circuit and the mains rectifier filter circuit. The on/off circuit belongs to the type of cutting off AC input voltage (as shown in Figure 1), and it should be checked whether the on/off control circuit is normal.
(2) If the voltage at the C-pole of the switch tube is normal, test whether the voltage at the B-pole of the power switch tube is normal between 0.4 and 0.6v at the moment of startup. If it is 0V, it indicates that the starting circuit of the switching power supply is open or the related components of the switch tube b and e are broken; If there is a normal voltage at the B pole of the switch tube at the moment of startup, but it immediately drops to 0V, it indicates that the starting circuit and related components of the B and E poles of the switch tube are normal, and the fault is in the oscillation circuit (including positive feedback resistor, capacitor, discharge diode, positive feedback winding of the switch transformer and its connecting circuit).
(3) If the oscillation circuit is found to be normal, measure the output voltage of power supply+b1 immediately after starting the machine. If the voltmeter shows a small reading instantly and then quickly drops to zero, the fault may be:
1) Pulse width or frequency control circuit (including control circuit that relies on the conduction of the optocoupler to force the switching power supply to stop oscillation or to achieve standby by weakening oscillation. For example, the Konka "06" series color TV switching power supply belongs to this type, and the output voltage of the switching power supply during standby is only 1/9 of that when turned on, making the color TV sound and light completely disappear);
2) Load short circuit (referring to parallel type switching power supply, as series type switching power supply will not stop vibration due to load short circuit);
3) Switching power supply causes protection circuit action due to output overvoltage or overcurrent (including misoperation caused by damage to the components of the protection circuit itself). The distinguishing technique and steps for this fault are: use a 500W AC voltage regulator to connect to the mains, connect the input end of the TV power supply to the output end of the voltage regulator, and adjust the output voltage of the voltage regulator from 100V (monitor with a meter).
