Re: Tektronix 475


Roger Evans
 

Have you obtained and read the manual. It should explain how the CRT grid supply is obtained by rectifying the output from the high voltage transformer, but the output 'sits on top' of the voltage generated by the Z axis amplifier. The Z axis output varies with the setting of the brightness control and also with a voltage generated by the timebase circuitry which turns the beam on during the sweep and blanks the beam during retrace. You say that when you press the beam finder you see a vertical line, if this is with an input to the Y amplifier then that is normal. If you can move the line horizontally with the X position control then that shows the X deflection voltage is getting to the X plates but the timebase is not running. The trigger mode should be 'auto' to make sure the timebase runs in the absence of a trigger signal.

You have no evidence the CRT is bad. You do appear to have evidence the timebase is not running.

Roger

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