Resistor or jumper at hv rectifer socket: Zenith 25mc30

[Tubejunke]

Originally Posted by NewVista

Is HV actually set to 25kv on these? What is the procedure for setting the efficiency coil?

25Kv is generally where most people seem to set them and many manufacturers recommended. The efficiency coil is used to set the cathode current of the horizontal output tube. You have to place a meter in series with the grounded cathode of the tube. There are a few opinions on the ins and outs of how the meter is set up, but I simply broke the cathode to ground connection and ran two leads out so I could check this current anytime I want. Some people believe in placing a capacitor across the two leads to protect the meter. You may want to look into that, but I didn't worry with it and had good results.

Other than that you operate the set normally and turn the slug slowly and find what is called the "dip" point or the point where the lowest current flows and that's about it. If you are like me, you won't be satisfied with that current as it may still be too high due to some other component causing that condition. I hope this helps. I think you can Google setting the cathode current on a vintage color television" and there is a pretty in depth article on this topic, but it is a bit scattered in nature. If you find it you will see what I mean.