CRT and Power Supply
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The high voltage section of the CRT is unchanged from the original vacuum tube oscilloscope used as the basis of this design.
The CRT requires shielding from the main power transformer. Cold roll steel around the CRT does not provide enough shielding from the 60Hz magnetic field. There are certain nickel alloys, such as mu-metal, that provide 100 to 1000 times the magnetic shielding as steel. Mu-metal can be purchased in a foil that can be wrapped around the CRT. A design using high voltage transformerless switching regulators (TOPSWITCH, etc.) should be considered to eliminate the vacuum tube diodes and the main (heavy) transformer in this circuit.
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