ctc12 clone beam current

[Bill R]

Originally Posted by DaveWM

blue should go to focus coil(w/100k mounted to focus coil),1.5 meg (part of shunt reg circuit),10k(part of boost supply circuit),.12 cap,bottom winding of fly.

BOTTOM WINDING OF FLY NEEDS TO BE CONFIRMED

The other end of the .12 cap goes to a tap on the efficency coil. That all sounds correct.

If Boost is low it is because your HV is low. Since you had 30KV with the regulator cap off I would assume it is capable of producing the 24KV needed under load. Low HV could be caused by insufficent drive from the H out tube, or from excessive load on the HV section. For now the screen voltages on CRT pins 3 7 and 11 may be close. Looks like Boost is 750 to 800 volts. The B+ should be 395 volts. So the screen voltages should be between 400 and 800 volts. Look at the CRT cathode voltages. They should all be close to 300 volts. These are controlled by the kine bias and drive controls. Double check the kine bias pot, and the resistors on either side of the kine bias control. The video out tube and associated circuit can also cause retrace lines and blooming because it can cause the CRT to draw excessive beam current. I would verify the componants in the 12BY7 video output circuit. There are several high wattage resistors between the plate and the Kine bias control and you could have some leaky capacitors. Oh yeah, do check the video output tube.
In a normal gray scale setup you start with Kine bias all the way down and the drive controls all the way up. You adjust the screen controls for a barely visible line. If one color does not make a line you leave that screen control up and increase the kine bias to produce a barely visible line, then bring the other colors screen controls up to match. With a normal brightness Black and white picture on the screen adjust the drive controls to eliminate color shading. One of the drives will usually be at max and you reduce the other one to eliminate shading.
If the CRT current is high and it is loading the HV section the Regulator current will be low. Regulator current should be between 85 and 140 milliamps.
I am a little curious about the screen voltage not going below 584 volts. Maybe the CRT is conducting to hard due to improper bias on the cathodes. Hmmm.