Switching transformer detector making circuit diagram

Probe domestic switch needle KG-300K needle head diameter is 3.0mm normally open switch needle

(1) Production and principle The S-11 color TV switching power supply produced by Zhengzhou Sancai Electric Appliance was changed into "switching transformer detector". The circuit is as shown in Figure a: Figure b below is the symbol, referred to as "detector".

Before the main power supply +130V, the switch transformer 10 is soldered with a red line a (for the positive test lead): then a black line b is drawn from the 10 feet (ground) (for the negative test lead). As shown by the dotted line in Figure a below. Thus, the high-frequency switching voltage signal of about 130V is taken from the two test leads a and b for detection.

Connect a 220V/200W incandescent bulb DN1 in the AC220V input circuit. As shown in Figure b below:

When the detected internal winding or peripheral circuit of the switching transformer is short-circuited. DNI illumination: DN1 is off when there is no fault.

The switching transformer detector (referred to as "detector") is completed.


Disconnect the 12-pin of the switching transformer T901 from the 3 pin of the original power supply integrated block N901 (STR54041) (internal switch c pole), and indirectly connect a 220V/40W bulb DN2 to the 10th and 12th legs of T901; ”

The positive pen a is connected to the 1st pin of T901 (main power + 115V front), and the negative test pen b is connected to 3 feet (ground).

Connect the “detector” to the AC220V power supply, and the bulb DN2 will normally emit light. DN1 is not lit. It indicates that the tested switching transformer T901 is intact: the secondary winding peripheral components (diode, filter capacitor, etc.) have no breakdown or short circuit.

Detection principle: The high-frequency switching signal voltage is output by the “detector” through the test leads a and b, and sent to the secondary windings 1 and 3 of the detected switching transformer T901. After 1191 boosting, the output from the primary winding 10 and the @ foot is near. The 250V high frequency voltage lights the bulb DN2. The DN1 is not bright, which proves that the load is not heavy, that is, there is no short circuit inside the switching transformer, and the diodes and filter capacitors connected around the switching transformer have no breakdown. The switch module can be repaired with the 2006 module. The red line of the module is connected to the 12 pin of the T901, the black line is grounded (the negative end of the C908), and the green line can be cut off. The circuit is omitted.

At the time of testing. If DN2 is not lit. DN1 is bright. It indicates that the T901 is seriously short-circuited inside. Or diodes and capacitors in the winding peripheral circuit are short-circuited. The faulty components should be eliminated one by one before they can be repaired with the 2006 horizontal block.

(3) Using the 2006 module to make a "detector"
On a pair of EE-type ferrite cores with a cross-sectional area of ​​1.5cm x 1.85cm, use a 0.51mm enameled wire to wrap around 72 turns as the primary coil L1. The secondary coil L2 is wound around 32 匝, and I3 is wound around 匝: connected to the LED indicator of the LED.

The +300V high voltage is obtained by D1—D4 rectification and C1 filtering. Switching transformer T1 primary winding L1 start to connect +300V, the end is connected to the 2006 module red line: the module black line is grounded, the green line is cut off, as shown below.