Huamei Universal FBT/ Flyback Transformer A21
Ⅰ、General Theories
Huamei FBT is actually a line output transformer with high voltage out put and complete genres.Refer to Figure 1 for internal principles.
From Figure 1 we can see that Color TV line output volt age is comparatively high in compliance with requirement of most color TVs.Therefore,as long as there is appropriate connection pin,it is reliable to replace Color TV line of original machine.
Ⅱ.Connection Method
Figure 2 is a description drawing of this Color TV line,with two circles of pins inside,in which pins at internal circle are shorter,these are leading feet of internal functions;pins at outer circle are longer,these are all empty pins.During application,make different connections among pins of internal cirele and outer circle,pins at outer circle have pin functions of line out transformer for color TVs,then weld outer circle pins of this Color TV line to original machine,so as to realize replacement of original Color TV line.
Caution:prior to installation of all-purpose Color TV line,please make sure to unplug Video amplifier board of original machine.After installation of all-purpose Color TV line,please test filament voltage,video amplifier voltage and voltage of acceleration node to be normal,and install TV amplifier board later,or it can easily damage the kinescope.
Ⅲ.Application Examples
When applying ail-purpose Color TV line output transformer,it is imperative to verify function of each pin.Pin sequence marking for line output transformer of each color TV vendors is different,clockwise or counter-clockwise.Therefore,when verifying function of each pin for color TVs,only by looking at drawing of the original machine is not enough.It is necessary to associate actual PCBs to determine the function of each pin.
Next is an explanation of Changhong D2118 color TV for instructions:
Figure 3 is a pin function figure for line output transformer of Changhong D2118 color TVs.After determining function of each pin from line output transformer of the original machine,it is viable to connect corresponding internal and external pins of all-purpose Color TV line.Methods are using sections of short lead wire to connect corresponding pins of all purpose Color TV line,see Figure 4,making functions of each pin at outer circle correspondent to function of each pin of Color TV lines in original machine.(Note:pin quantily of outer cirele for purpose Color TV line might be different from the pin quantity of Color TV liine of original machine.During connection,it is imperative to select one which is closest to pin position of original machine,so as to install all purpose Color TV line on PCB.) After connection of each pin and confirmation of correction,it is viable to inter modified external pins of all purpose Color TV line to welding hole of each pin from original Color TV liine for good welding.(Useless extermal circle pins can be cut off).Therefore,connect high and medium voltage,starup for adjustment,and speed up and focus the voltage.
Ⅳ.Troubleshooting
1、How to detect functions of each pin for Color TV line of original machine without drawing?
2、When there are no drawings,it is easy to detect power supply pin,line output transistor C machine and grounding pin of Color TV line in original machine.Video amplifer and filament pin are mostly connected to rear board by lead wire,and video amplifier is connected to the rear board after rectifying and wave-filtering,wave-filtering capacitor has a withstand voltage of 250V,therefore,it is easy to find video amplifier voltage pin and filament pin.Characteristics of ABL pin is:a certain pin of Color TV line is connected to the ground with a 0.047-10uf capacitor,and connect to light control PCB with an ABL pin through an electric resistance+14V,-14V,25V and 45V are mostly power supply for output circuit.Under normal conditions,positive and negative nodes of 14V are used together for a field output circuit;14V and 45V are used together for a field output circuit,25V power supplying is a certain field output circuit,so it is effective to make judgment of line change pin voltage which is connected to field output circuit.Pulse pin is normally wired through resistance capacitance and delivered to AfC pin of line scanning module and line pulse input of decoding module.Therefore,it is viable to find the pin by analyzing generous functions of each section of electric of original machine Of course,if there is a book of replacement material for line output transformer,it would be easier to make judgment on pin function.
2、What can we do if there is no individual coil from Color TV line of original machine?
Multiple voltage output of all purpose Color TV line is capable of supplying requirements from most color TVs.But individual voltage for a minority of color TVs is not available for all purpose Color TV line.By then,it is viable to use enameled wire or fine flexible cord to circle on magnetic cord of all purpose Color TV line to acquire necessary voltage.But it is worth noted that when adding up the coil,it is imperative to start from fewer circle to more circles,and add circles while testing the machine.It is forbidden to connect electric circuit for machine testing after adding up too many circles,or original machine can be damaged by high voltage proudcted by added coil.
To repalce double-focous color lines of flat color TV sers,connect the two focusing electeodes of the original television and attach them together to the focusing line of the universal color line.
3、After installation of all purpose Color TV line,what will happen if there is too lager or small of row width?
After installing all purpose Color TV line,when row width is too large or small,it is imperative to make adjustments to row width potentiometer,apply the following methods for adjustments:when row width is too large,it is viable to use larger size correction capacitor or reduce interval capacitor to solve the problem.However,maximal changing volume of interval capacitor can not exceed 20% of original capacity,or it is easy to damage line output transistors.When row width is too small,it is viable to use small size correction capacitor or enlarged interval capacitor to solve the problem.
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