Quote:
Originally Posted by Dubis7
I'm seeing the pin output for the Yoke on the schematic, but my confusion is arising from the fact that it lists a different resistance for the horizontal and vertical windings. How can I tell which winding set I'm measuring?
That being said, is a yoke really supposed to be receiving enough voltage to spark like mine did? These were big sparks - think the size I'm supposed to be getting from my flyback, but from the yoke.
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If you trace the wiring on the schematic you see that the horizontal output circuit is connected to pin 4. The yoke coil connected to pin 4 ends at pin 8, so the horizontal coil is between pins 4 and 8, resistance should be about 33 ohms. That coil is also center tapped and connected to pin 5, so from pin 5 to either pin 4 or 8 you should measure 16-17 ohms. Likewise you can trace the vertical connections on the schematic to pins 1 and 2, and measure about 26 ohms. You don't have to just go by the diagram of the the yoke as a separate unit, you can use the rest of the schematic to give you clues. The sparks were a result of the current jumping a gap, it could be were the wire broke or because the voltage rose so high the current jumped to somewhere it should not have. Do remove any carbon tracks you find.
The way the horizontal output works is that the current passing through the flyback and yoke that scans the beam across the screen suddenly stops at the end of a line. The flyback and the yoke are inductors, when you stop the current through them suddenly they react by producing a voltage spike (several thousand volts) that tries to continue the current. This voltage spike is stepped up further by the flyback transformer to provide the anode CRT anode voltage. It also generates the boost voltage. The narrow spikes is why there has to be some capacitance to smooth them out to a level DC voltage after they are rectified. BTW, the ignition on a car engine use the same technique of cutting off the current through a coil to generate the spark.