Tektronix 465 horizontal focus issue

[sean0118]

Just a note - don't get DeOxit anywhere near the Y channel input  attenuator contacts. The attenuators are on a special substrate and it's strictly IPA only for those, the cleaning procedure (if needed) is in the manual, it involves sliding IPA soaked paper between the closed contacts using just horizontal movement. Vertical movement (lifting the contact springs) will result in reduce contact pressure.

Impedances are high - I once traced a noisy input channel to a stray eyelash on the attenuator PCB.

Thanks, good point, I saw those contacts but left them alone as they look very delicate. Thanks for the warning though as I do have a habit of putting DeOxit on everything. 

There is no calibration adjustment for offset in ADD mode on the 475.  You have to use the position controls after ADD mode to zero the trace.

The reason for the offset is that the CRT amplifier has some offset so centering the trace actually requires the vertical input to have an offset, and when ADD mode is used, the offset from both channels gets added together.

Interesting, maybe mine is working as intended then. Anyway, I'm going to borrow an adjustable reference and do the cal properly, I will report back the results then.