Digital Display Circuit Diagram

Testing Flyback Transformer - How to test and when to replace

Today, more and more monitor comes with flyback transformers problems. Testing flyback transformers are not difficult if you carefully follow the instructions. In many cases, the flyback transformer can become short circuit after Use no more than two years. This is partly due to bad design and low quality of materials used during the manufacture of flyback transformers. The question is what such problems can be found in a flyback transformer and how to test and when in place. Here is an explanation that will help identify many problems Transformer.

There are nine common problems can be found in a flyback transformer:

a) A shorted turned in primary winding.

b) A open or shorted internal capacitor in the secondary section.

c) Flyback Transformer is bulged or cracked.

d) outside Arcos land.

e) arcing between internal windings.

f) short internal high voltage diode in secondary winding.

g) Breakdown focus / screen voltage divider causing blur display.

h) Flyback Transformer breakdown at full operating voltage (problem when under load).

i) Short circuit between primary and secondary.

Testing flyback transformers is based on (a) and (b) since problem (c) is visible while problem (d) and (e) can be detected by hearing the sound generated by an arcing flyback transformer. Problem (f) can be checked with multimeter set to the highest rank of measurements from anode to ABL pin while (g) can be solved by adding a new monitor blur buster (For 14 "and 15" monitor only.) bug (h) can be tested only by substituting a similar known good flyback transformer. different monitor have different kinds of flyback transformer design. Problem (I) can be checked with an ohm meter measuring between primary and secondary. Short or became open in the secondary coil is very rare.

What type of symptoms will return if there is a short-circuit the primary winding back?

a) No display (No high voltage).

b) Power open and close.

c) voltage drop from B +.

d) horizontal output transistor will get very hot and then shorted.

e) Along B + line defective components. Example: - secondary diode UF5404 and B + FET IRF630.

f) Sometimes it will cause the power section of a sudden.

What kind of symptoms appear if a capacitor is open or shorted in a flyback transformer?

Capacitor shorted

a. No display (No high blood pressure).

b. B + voltage drop.

c. Secondary diode (UF5404) will burned or shorted.

d. horizontal output transistor will get shorted.

e. Power open and close.

f. Sometimes power section will blow, for example: Raffles 15 inch monitor.

g. turn feed section for example: Compaq V55, Samtron 4bi monitor.

h. Sometimes the automatic limiter brightness (ABL) circuitry components are burned.

This circuit is usually located beside the flyback transformer. For example: LG520si

Capacitor open

a. High voltage shut down.

b. Monitor will have 'the sound of tic - tic. Sometimes the capacitor can be measured well, but break down when voltage under full operating.

c. horizontal output transistor will blow in a few hours or days after being replaced.

d. Sometimes is intermittent will make "no show".

e. that is, distorted screen, the screen in and out.

f. This will cause horizontal output transistor to become shorted and blow the power section.

How to check if a primary winding is good or bad in a Flyback Transformer?

a) By using a flyback / LOPT tester, this instrument identifies faults in primary winding by a 'ring' test.

b) You can try the liquidation, even with only a short turn around.

c) This meter is handy and easy to use.

d) Only simply connect the probe to the primary winding.

e) Reading is a clear 'bar graph' display which show you if the flyback transformer primary settlement is good or shorted.

f) The LOPT Tester also can be used to check the mode CRT YOKE coil, B + coil and the transformer switch winding power.

NOTE: Measuring the resistance winding of a flyback transformer, yoke coil, B + coil and SMPS winding using a meter may mislead a technician in the belief that a settlement short of good. This can waste precious time and time is money.

How to diagnose if the internal capacitor is open or shorted? By using a standard analog meter and a digital capacitance meter. A capacitor good with the range of 1.5 to 3 .* nanofarad nanofarad

1) First set your multimeter X10K.

2) Place the probe to the anode and the cold floor.

3) You must remove the anode cap to get an accurate reading.

4) of the cold: the monitor's chassis ground.

5) If the needle of the multimeter shows a low ohms reading, this means that the capacitor is shorted internally.

6) If the needle is not move at all, does not mean that the capacitor is well

7) You have to be confirmed by a digital capacitance meter that you can get one of the local distributors.

If the meter reading shows 2.7nf digital capacitance, this means that the capacitor is within range (OK).

9) And if the reading showed 0.3nf, this means that the capacitor is open.

10) You have three options if the capacitor is open or shorted.

- Install a new flyback transformer or

- Send the flyback transformer for refurbishing or

- Send the monitor back to customers after spending many hours and much effort on it.

* However, some monitors can be set to 4.5nf, and 7.2nf 6NF. Note: Sometimes the pin capacitor is connected to internal circuits (feedback) instead of land.

RCA TV flyback transformer circuits usually do not have an internal capacitor it.

If you have a return time diagram and the circuits that you can get the network that would be an advantage to easily understand how to control them.

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