Horizontal help for a 20Y1 Admiral

[Penthode]

Originally Posted by 6GH8cowboy

I have checked and experimented slightly with component values and observed little change. I have even connected a negative bias supply at pin-3 of the osc control and still little change. Is it possible that a Miller 6183 is not a suitable replacement? When I was in the biz most coil needs were peaking coils that went open so I have little recall what these replacements did in sets like these. It seems that the native frequency of the circuit using this coil is wrong about 4 times what it should be after extreme adjustments. Component values have little effect on the gross frequency. My original coil was bad and the new coil does bring the circuit back to life, just the wrong freq. I am presently testing without a HO Tube. so no pulse from the FBT. I dont think this would swing the osc frequency this much if missing but like I said I artificialy ran the negative voltage up and down at pin 3 of 6sn7 control and the freq didn't change much.

Ah, yes. The classic RCA synchroguide horizontal AFC circuit! Even the component values are the same in the RCA sets. The lock coil is used for shaping the waveform to make the circuit more noise immune. You should be able to short out the lock coil and adjust the oscillator coil for horizontal sync. The alignment procedure should be readily available. Let us know if you do not have it.