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I have had some sets with problems in the 6BK4 circuit cause a very dim picture on a good crt due to low HV. Measure the 6BK4 current (voltage drop across the 1000 ohm cathode resistor). Current should be 800-1000 microamperes (about .8 to 1 volt drop across the resistor if I remember correctly). There is 400 volts on both sides of the resistor. In an older set like this one, the resistor may not be in place, though.
If you have an HV probe check the CRT HV, you will probably find it low.
Also have had a 6BK4 that drew too much current and pulled down the HV too much. Replacing the tube solved the problem. I have seen the glow in the 6BK4 but I don't think its any problem.
Worked on a set this week where someone had turned the HV control all the way up and you could hear arcing, picture was very blurry...turning down the HV control really made a difference.
Last edited by Chad Hauris; 02-27-2005 at 03:02 PM.
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