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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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1 Answer

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...

Mar 05, 2015 | LG Televison & Video

1 Answer

what is "flyback" in a tv monitor


A flyback transformer (FBT), also called a line output transformer (LOPT), is a special type of electrical transformer. It was initially designed to generate high voltage sawtooth signals at a relatively high frequency. In modern applications it is used extensively in switched-mode power supplies for both low (3V) and high voltage (over 10 kV) supplies.

this is use only on monitor the old one that used CRT TUBE.
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Dec 01, 2013 | Samsung SyncMaster 793DF 17" CRT Monitor

1 Answer

flyback no. of cmt 2198


The B+ of your CMT 2198 TV seems to be about 95V.

• Have a time to read about these tip:

How to test Flyback Transformer Without taking it off the Board

While we search for your flyback transformer T751 part number





we will let you know.. .

Jul 31, 2012 | Hitachi CMT-2195 21" TV

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