Re: Tektronix 475


I have about -20 V between the first grid and the cathode, so I cannot see why the beam finder does not display at least a spot. I only saw a very faint vertical stripe with no input on the Y amp. An absence of spot or trace generally indicates an HT fault, but all HT voltages are OK.
From your explanation a running time base is required for a display, but I thought the beam finder would override that. I will check the time base circuit with another scope.

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