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Well, I've been working on the DC convergence some more. If you look at picture ...002 attached, you see the DC convergence in the earlier chassis, and in pic ...003 you see the later chassis I have where the blue lateral changed to a permanent magnet. In this case a 82 hm resistor has been added so that the circuit draws the same current. The reason is, this whole mess is the cathode resistance for the horizontal sweep output tube! The DC in the convergence coils is developed between the tap on the potentiometer and the wiper on the potentiomenter. Since I can't get tapped potentiomenters, I am going to use the circuit in pic ...004. The fixed resistors supply the tap point, and the three 250 ohm pots supply the variable voltage. Hopefully, the extra resistance won't reduce the dynamic current too much. We shall see.
The blue DC pot was open end-to-end as well as having a big bad area where the wiper is open. The resistance to ground at the cathode of the HO is supposed to be about 25 ohms, and measured 70 ohms. Maybe this is why the set has been sensitive to particular choice of HO tube.
I put the 250 ohm pots in a little open-backed plastic box, which I planned to mount just behind the cabinet back, so the shafts will protrude through the holes in the back. One oops - I forgot that the back insets into the cabinet frame, so there is no depth left to mount the circuit box. Will have to add a bracket of some kind.
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