Horizontal collapse k7400 *solved*

curtislv426

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Hey guys. I have horizontal collapse on a k7400 chassis. The only component I have found faulty was an open r104. I replaced it and I still have horizontal collapse. I also gave a it a full capkit and that didn't help either. My b+ is perfect at 117. The flyback does not energize the tube either. I replaced it with a know working flyback as well. The power circuit passes the lightbulb test. I can also connect the lightbulb to the horizontal yoke header that connects to the middle leg of the h.o.t and I also get 117-120 volts and a lit lightbulb. Q101 tests good, Hot tests good ( I replaced it with an FJL hot as well), switching mode power supply chip test good, and q703 tests good. I have not seen this problem before. My test tube is also good and the yoke is not damaged. Thanks for any assistance.
 

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U701 the LA chip is the only thing i can think that could cause a weird issue like this. Idk you got me on this one.
 
Ok .no change after u701 replacement. I'll swap out the little power supply chip and q703 and see if that helps
 
I was assuming you checked r760 r765 q703 right? This is a bad component on the horizontal side. Has to be if youve ruled out simple things bad pots on the control
Pad, bad connections from the control pad to the deflection board, the more i think about it control pad issue could cause this.
One is 100ohm other is 33k dont have it memorized yet to which one but easily detectable

Edit:
On a 7400 idt it has one
Of those two resistors i mentioned they did revise it quite a bit from a u2000
 
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R760 and r765 are not populated on the K7400 chassis. I checked q703 and it tests good, same with the power supply chip.....

No change with new q703
 
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The flyback does not energize the tube either
It does or you wouldn't have a picture, albeit collapsed, without flyback operation/high voltage.

Check continuity from the pin of the H deflection header and the pin of C722 indicated here and check the solder joints of C722 (and its capacitance too), L701, C720, R732 and of the header:
C722.jpg
And continuity across the other pin of C722 and the anode of D707:
C722b.jpg
 
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It does or you wouldn't have a picture, albeit collapsed, without flyback operation/high voltage.

Check continuity from the pin of the H deflection header and the pin of C722 indicated here and check the solder joints of C722 (and its capacitance too), L701, C720, R732 and of the header:
View attachment 855540
And continuity across the other pin of C722 and the anode of D707:
View attachment 855542
Thanks so much MKL. You are truly awesome. I didn't have continuity from anode of d707 to the other pin of c722 (width cap). I examined L701 and it had broken solder joints connecting the wire to the legs. I now have full deflection and a working chassis. Many thanks.
 

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