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Flyback xfmr substitiute

I need a sub for the flyback on a kv-25xbr about 20 years old. Part no. 1-439-339-12. I changed the horizontal oscillator transistor which was getting super hot; but still getting low voltage from the xfrm

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Hi and welcome to FixYa,

Initially, have you tried here, here or here?

To verify FBT, a ring test would help.

Good luck and Thank you for using FixYa.

Posted on Jan 08, 2009

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Click here to find the FBT.

Posted on Jan 08, 2009

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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

Tip

How to test Flyback Transformer Without taking it off the Boarda) Basically it...





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:


7_31_2012_2_32_48_pm.jpg

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

with the horizontal drive and horizontal output transistor



sample of H out transistor

7_31_2012_2_38_05_pm.jpg


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).






7_31_2012_2_42_22_pm.jpg


• 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.





7_31_2012_2_47_50_pm.jpg





• These only applies to CRT type TV's.

on Jul 31, 2012 | Philips Televison & Video

Tip

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


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

to work.

sample picture

f3f741f.jpg







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

with the horizontal drive and horizontal output transistor

58689de.jpg






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 tube.


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.

here is a sample image

ab6c901.jpg



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.

sample of H out

b3363d6.jpg


These only applies to CRT type TV's.

on Dec 24, 2009 | Music

1 Answer

I have a Sony model KV-32S26 that will not turn on, been sitting for about 2 years. Had a tv repair guy tell me it was the flyback transformer. If that's the case, can I replace it myself? Thanks


1) You must test the a) fuse b) c.breaker inside c) diode, d) rectifier e) transformer f) filter. g) IC. regulator voltage and test it. If the problem persist you must go to the horizontal problem by lack of RASTER, now you test the transistor horizontal power, flyback. If you have some experience with the electronic you can try. If do not, better go to the repair shop Tv. Since you can have a electric shock by H.Voltage discharge.
God bless you

Oct 11, 2012 | Sony KV-32S26 32" TV

1 Answer

Sony kv-32fx60b only horizontal line no vertical ,(vertical ic (stv 9379)all ready replaced,problem same,ic voltage ok ,how to check vertical saw signal coming or not?


A smarter way is look for the source voltage--if the chip failed it got a resistor between it and the FLYBACK which is where the approx 30 volt source comes from for vertical---follow it to the xfmr.--there will be a open resistor in that line.

May 29, 2012 | Televison & Video

Tip

How to test flyback without taking it out of the board


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

to work.

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

with the horizontal drive it should generate output voltages on the

secondary terminals

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

voltage, the heater lit when flyback is good.

d) having a voltage reading of 75 V or lesser on its 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.

on Dec 03, 2009 | Televison & Video

2 Answers

6 blinks and no picture. Solution said no horizontal but what does that mean?


It means you have a high voltage problem on the main board, without this no picture can be generated. This will require a tv tech to troubleshoot the problem.

Jan 04, 2011 | Sony FD Trinitron WEGA KV-34HS420 34" TV

1 Answer

Standby light blinks you hear the contactor clicking in set, no audio and no video displayed. sony kv-36Hs500 only looking for response if this is free of charge


this symptom is usually caused by a breakdown in power supply circuit or it may also be caused by a breakdown in the horizontal deflection circuits which includes horizontal oscillator, pre drive or drive circuits, horizontal output transformer, horizontal output transistor and high voltage circuits (flyback transformer). pls observe precautions in dealing with this high voltage circuits and if so happen you are not inclined with this kind of work, it is better for you to bring it to a qualified technician to avoid accident. good luck!

Jul 27, 2010 | Sony FD Trinitron WEGA KV-36HS500 36" TV

1 Answer

Wega KV36HS510


resolder all parts around the flyback.flyback also..then check the horizontal transistor it maybe shorted...weng

Oct 16, 2007 | Sony FD Trinitron WEGA KV-20FS120 20" TV

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