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How to test Flyback Transformer Without taking it off the Board

How to test Flyback Transformer Without taking it off the Board

a) Basically it has to be acted upon by a supply voltage of at least 95V

to work.

sample picture:

b) Of course, assuming the horizontal deflection oscillator works, same

with the horizontal drive and horizontal output transistor

sample of H out transistor

It would generate output voltages on the secondary terminals

and 200V line will be active sending voltages to the

Video Drive circuits. Of course high voltage will be generated

ranging to at least 30 KV and there will be voltages on the G2 of the CRT.

c) The easiest test point to look when it is oscillating, is the CRT heater

voltage, the heater lit when flyback is good ( mostly at night times when it

is dark ) and you can hear sounds, too ( if speaker is connected).

• Heater : marked with letter H and H1

• Green Arrow for the G2 voltage

d) Having a B+ voltage reading of 75 V or lesser ( primary pins )

indicates a bad or partially shorted flyback, assuming your

horizontal output transistor and power supply are good & OK.

• These only applies to CRT type TV's.

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I need help with repairing HP z74 CRT monitor with power failure...

If your HP z74 CRT monitor is not turning on, there could be several potential causes. Some common causes of power failure in CRT monitors include:
  • A faulty power supply: The power supply is responsible for providing power to all the components of the monitor, so if it is not functioning properly, the monitor will not turn on. You can test the power supply by using a multimeter to measure the voltage at the output connectors. If the voltage is not within the expected range, the power supply may need to be replaced.
  • A faulty flyback transformer: The flyback transformer is a critical component of a CRT monitor, as it converts the high voltage AC input from the power supply into the low voltage DC output required by the other components of the monitor. If the flyback transformer is faulty, the monitor will not turn on. You can test the flyback transformer by using a multimeter to measure the voltage at the output terminals. If the voltage is not within the expected range, the flyback transformer may need to be replaced.
  • A faulty or blown fuse: The fuse is a safety device that protects the monitor from damage due to excessive current. If the fuse is blown, the monitor will not turn on. You can test the fuse by using a multimeter to measure the resistance across the fuse. If the resistance is very high or infinite, the fuse is blown and will need to be replaced.
To diagnose the specific cause of the power failure on your HP z74 CRT monitor, you may need to open the monitor and perform some basic tests using a multimeter. This will help you identify the specific problem and take the appropriate steps to fix it. It is important to note that working on electronic equipment can be dangerous, so if you are not familiar with electronics repair, it is best to seek the assistance of a qualified professional.

why not flyback oscilate or fly back voice?

I am unable to give any specific advice but if there is voltage or power to the Line Output circuit then its possible a short or load exists on the flyback transformer which causes a shutdown in this circuit.
I am afraid practise and knowledge of a particular model is a great help to find its faults.
The Flyback transformer (if like I remember) will have sub power supplies from it to drive audio, frame etc so a short on these will cause problems, also the rectifier diodes to these can fail you may need to remove one end of a diode for accurate testing.
Another failure point in power supply rails is capacitors which go open circuit this makes their voltage line unstable, also on the capacitor problem list are those around its flyback circuit that act as snubbers to tune it, these were at my time little blue capacitors of several KV which had a habit of shorting or change value.
Any of these will disturb a balanced start up cause a spike and shutdown.
Without particular knowledge of a model and its circuit I am unable to help further, I would look for shorts on Diodes and components, disconnect supply rails to audio and frame if they come from the flyback transformer (these are the heaviest loads and will only serve those particular circuits) then it will possibly capacitors gone o/c (I used to carry a cap tester years ago which used a 555 ic easy and robust).

Hope this helps in some way...

hi i m sanjay i m having sony colour television kv-2782me7 i found some problem in power supply section i m geting low voltages frm secondary output i want 135 ,25 ,8 , and -33dc voltages bt i m geting only 50 ,6 ,2 and -10 dc voltages i checked all components in secondary section bt i could nt found any diffective component can u help me plzzzz

there is a possibility of a shorted turn of the flyback transformer. To test. short B-E together on the horizontal output transistor and connect 60W globe across C-E. measure voltage across lamp - if it comes up to 135v then you have a short either in the horizontal circuit or secondary circuit off the flyback transformer or even the transformer itself.
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