Monitor and television flyback transformer have some
similarity except only on the internal capacitor. Monitor flyback
transformer have the internal capacitor to improve the picture quality.
Without the internal capacitor the display will bend or slightly out of
shape especially at both the right and left hand side of the picture. Most
flyback transformer will have ten pins at the bottom of the flyback. Each
pin serve a purpose or function as part of a complete circuit. The common
pins that you can find in monitor flyback are:
B+, H. collector pulse, ABL, GROUND, G1, AFC, VCC, HEATER and X-RAY PROTECT.
B+ and horizontal collector pulse forms one winding which we call it as flyback primary
winding. This is the most important winding and easily develop a short
circuit when B+ line or Horizontal output transistor have problem. Sometimes
a shorted internal capacitor in the flyback may cause the primary winding to
burn internally. The only way to test it is to use a flyback or lopt tester.
Normal multimeter can't check this kind of problem.
Next is the ground,G1, and AFC winding. AFC stand for automatic frequency
control and it send
signal from the flyback to the horizontal oscillator ic to lock or
synchronize the frequency
of the monitor. If this afc line have problem the display will shift either
to the far left or far
right. There is no way you can adjust the picture to the center. The
function of G1 is to pull the electron
generated from the cathode and channel it to G2 which is the screen voltage.
G1 normally is negative
voltage. If there is a missing G1 voltage to the picture tube the monitor
display will become
very bright with flyback lines across the screen and sometimes the monitor
will goes into
ABL stand for automatic blanking limiter- I refer it as contrast circuit.
Why? because whenever there is a
contrast problem i will look for this pin and begin to trace from there.
Normally a high ohm resistor
and a shorted ceramic capacitor caused the display to become dim and you
think it might be the fault
of a defective picture tube.
Heater pin nowadays hardly found in monitor flyback because the crt heater
voltage derived from the switch mode power supply.
Heater pin still can be found in television flyback. If the anode voltage is
too high, x-ray protect pin will send
a signal to horizontal oscillator ic to disable the horizontal drive
waveform. Without drive waveform the high voltage
will collapsed and protect the user from excessive x-ray generated by the
abnormal high voltage. The flyback transformer will also generate high pulse
ac which later convert to dc voltage as a supply voltage to certain
circuit such as the vertical circuit. If you truly understand how a flyback
transformer work and the functions of each pin, troubleshooting
monitor or tv will be much easier.