To the TV master - About TVs.

MSF #22
Track: Lame must live !!!                
Author: Macros/Kotlas town. Fressshhh... 
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       Hello to all TV masters!         

  Just recently they brought it to me for repair.
TV box - "Dawn", it seems, it's called.
Nope, not tube... On transistors.    
  Well then. You plug it into the network - and from
there's smoke coming from it. Kotsoft joked - more
put a fan and there will be smoke
car :)                                
  There is nothing to do - it needs to be repaired.
In short, through the rezuk, which was burning,
the power supply supplied a voltage of 96 volts
for a fee. It is clear that the rezuk burned due to
overload in the circuit after it. Just for now
I understood this, the rezuk finally died.  

I started searching according to the scheme... Which one scheme? I didn’t have a diagram from him. I I used the scheme from
"Rekord" third generation, as it turned out that they coincide by almost 90% ;) In short, 96 V after this summary goes to line, and after it - to the transistor KT838 (so big, on the radiator). B the base circuit of this transistor is turned on secondary winding of the isolator transformer, and the primary - on emitter circuit of another transistor, to the base of which is supplied lowercase sync pulse. In short, in the end line windingmust arise oscillations, and the remaining windings used to create secondary supply voltages: for the kinescope filament, to the second anode, somewhere else... Well, that's it. The transistor turned out to be serviceable, and there is more short to ground there nothing could. During the experiments new shortcut, which I put in place of old, rather charred... There is nothing to do - you have to unsolder load from the remaining line windings. I unsoldered one - it still smokes, the second, the third... I unsoldered everything. I turn it on - it doesn't smoke less! How is this so, because I checked the line - there are no breaks, short circuits, it seems, too... But neither theoretically nor practically nothing could create overload in the circuit. Then I got to my TV and The liner fell out of it. I bet on that one TV box - everything works, and nothing smokes! Hehe... It turns out that in that native line there were short-circuited turns, which is why an overload was created. In general, the presence of short-circuited turns can be checked in any transformer using an oscilloscope. Collecting LC circuit, connect the generator and look.
Well, let's take things in order. This check based on the phenomenon of parallel resonance. Increasing the amplitude of oscillations on the low-frequency generator two or more times indicates that the frequency of the external generator corresponds to frequency internal oscillations of the LC circuit. To check, you need to close the secondary transformer winding. Fluctuations in circuit must reduce the amplitude. From it follows that short-circuited turns bypass the resonant phenomena of the LC circuit. The presence of short-circuited turns in L is also will lead to the inability to observe resonant phenomena in the circuit. In one word, if after you the secondary winding is short-circuited, phenomena resonance did not disappear, then the transformer should be considered faulty. This technique is described in Solonovskaya book "Repair of imported N7 TVs." Unfortunately, I have an oscilloscopeno, I take oscillograms using arrows voltmeter :) and in general I solder with the help cabbage soup lighters :) Pokedova, and don’t forget to have in your presence of several known good ones "particularly critical details", such as lineman, kinescope and spare TV... Just in case... :)

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