Open Winding In Yoke Coils
Well, I’m not sure about you and as for me so far after so many years in this repair line i had only came across only few PC tube that have open winding in yoke coils. It seems that yoke coils are more prone to short circuit compare to open winding. Horizontal yoke coil get shorted easily compare to vertical yoke coil most probably due to stress from the higher voltage and current to the winding. By using a normal ohm meter you could easily check if the winding is open circuit or not. To check for shorted winding in horizontal yoke coil, one have to use a Blue Ring tester.
If either one of the coil have problem (in a color picture tube) the best is to replace the whole picture tube. Yes in fact you can just replace the coil but you have to spend lots of time to adjust the convergence. The display you might get could be color patches all around the tube if you have decided to replace only the yoke coil. I suggest that you replace the pc tube in order to save time.