Flyback transformer tester circuit using 2SC828

[wiparat]

The circuit tests a flyback transformer of the televisions that the result is a simple, easy and cheap to build.
One of my friends is TV repairman colors – black and white. He said the repairing on the fly back is very difficult. Because it has large size, Is high voltage source. So is very dangerous.
- When the assumption that it is damaged. It’s not easy to testing. Need to know what the working principle, and a great tool. To reduce expenses and time.
Its internal structure is mostly coil over. Which are often damaged in many cases.
– Lack. lamps look like it. We are able to measure with a multimeter. Set the value of the resistance. If there is no resistance to it. In the lack of bad.
- But if bad in other ways, which is not very often is Short Round. He said that the cause may be due to the use it gets hot. The coil can be melt fused together. But we can not check that. In this way it was. Because when measured with plain meters. It is resistant to normal.
- When they solve the problem by buying a new trial backed fly replaced. That it is not wise Because of it is expensive and difficult to replace. Sometimes satellite TV owners will want to urgent.
- I suggested he try to build this flyback transformers circuit. It has the advantage of a simple, cheap and easy to use. Because of the things he used to have, almost would not have buy more it. And very cheap compared to the flyback one.

How it works
As shown below, as simple circuit with the two most important components are
- The oscillator circuit use a transistor Q1 (2SC828) is base works with three capacitors C1,C2,C3 and three resistor R1,R2,VR1 to To produce a sine wave frequency.
- The current amplifier and detect circuits has transistor Q2 (C828) is used to increase the signal to works with four resistor R3,R4,R5,R6, And R7 is used to limit current to the amp meter, If you choose the amp meter that use lower current, so use a resistance R7 increase up.



The part of this circuit
Q1,Q2_______2SC828 or 2SC2240 low noise, 30V 100mA NPN transistor
C1_________ 0.047uF 63V Polyester Capacitor
C2,C3______ 0.022uF 63V Polyester Capacitor
R1_________ 1.8K 1/4W Resistor
R2_________ 1K 1/4W Resistor
R3_________ 150K 1/4W Resistor
R4,R5 ______ 10K 1/4W Resistor
R6_________ 120K 1/4W Resistor
R7_________ 470 ohm 1/4W Resistor
M1_________ meter 1mA

Customization and bring to used.
Begin, place two probe at twin pins of the good flyback transformer, then turn on switch S1, if you can read the current approximately 0.1mA, Show that, the oscillator circuit is not working. to adjust VR1 reduce value its steadily With the observe the meter. If you read value is 0.4 mA, Show that, the oscillator circuit has already started.

If you try to bring the probe to touch together (Short together) to see that the meter needles falls down. Show that, this flyback transformer Short certain oscillator will stop running.

If measure transformer to the other, must adjust VR1 to meter reading is 0.6mA. If it normally, the meter needle will wiggle back and forth a little bit. If that transformer is “Short Round” the meter needle will down.
Source:

 

[fernando_g]

Nice circuit!
The only limitation I see, is that sometimes the short inside the transformer is not a dead short, but arcing that occurs at high voltage only.
But other than that, I think you have an excellent idea to test the transformer in a safe manner!

 

[Nigel Goodwin]

Pity it's so many years too late

But there have been excellent LOPTX testers available for MANY, MANY years - that work by 'ringing' the transformer, with the 'later' ones (20+ years old) using LED's to display the number of 'rings'.

This is an interesting concept, but I don't know if it would b as effective or not?.

As fernando_g mentioned, a common fault (other than shorted turns) is internal arcing, which none of the testers can test for - but as it's generally particular makes/models which are prone to it, it's easy to diagnose for professionals.

 

[unclejed613]

i remember an RS-232 terminal, don't remember who made it, but it had a short white flyback in it. the most common failure on that flyback is it would burn all the way around the white plastic right in the middle. not at the bottom, not at the top, but around the middle. sometimes the connection that went to the horizontal output transistor would burn a dime size hole in the circuit board as well