UPDATE, MARCH 12, 2019, DAY 224
THE SURGERY CONTINUES. From Mike:
“Greetings. The first “pass” at the high voltage cage is finished. I say “first pass” because the convergence pot issues are still experimental and I will likely need to make some component adjustments of the high voltage resistors that form the divider circuit on either side of the new pot in order to bring the convergence in to range. The reason for this is that the original pot is 60 megohm and the new circuit with the Zenith 63-7145 only has a swing range of 20 megohm. Some resistance is already built in to the Zenith part so that has to be considered in the calculations. I hope that convergence can be achieved within this new range. If not then I will be experimenting with the values a bit. The important thing that I need to adhere to is the original divided resistance value of the circuit since the 3 circuits (Focus, High Voltage Regulation, and Convergence) all interact a small amount by existence of these resistance values. The total value that I removed was between 230 and 240 megohms. My new value across the divided network is 219 megohms and there is a 7 megohm resistance built in to the new pot at the swing arm so that introduces some need for experimentation which I hope is soon to come. Also, I will soon need to address the issues with the crt socket. I have found a vendor but they are not responding to my queries about availability and cost. I may have to attempt a rebuild of the original socket.
Pict. #1 Old convergence pot left and Zenith 63-7145 right, mounted to the original bakelite panel with nylon screws and plates.
Pict. #2 The new circuit with experimental values shown.
Pict. #3 The original Focus pot which cleaned up nicely and seems to be OK. New wiring to the pot along with new capacitor (yellow) and High voltage 8 megohm resistor (blue) hard to see behind the cap.
Pict. #4 High Voltage cage with some, not all new wiring is complete. Note that the original 1AX2B focus rectifier tube is now solid state. (white stick near center). And the control shaft coupling to the new convergence pot was accomplished with a high quality piece of silcone rubber tubing. (lower right, orange) . And finally, all 3 of the H.V. rectifier tubes are replaced with a matched set of JAN Mil. spec 1B3’s.
Cheers, Mike”
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