2445B vertical non-linearity other issues.

Robin Szemeti

I have a 2445B that has gone a bit odd recently.

Ch2 and to a lesser extent CH1 have developed vertical non-linearity. Put a sine wave through it and it is obvious, a sort ot cross-over distortion around the centre of the tube .. Moving the trace around with the vertical position control it appears the distortion stays stationary and the trace moves through it. I also noticed the text had moved vertically off the bottom of the display ... and if I move CH1 or CH2 beams into the upper part of the display, the text starts to jitter and shake .. this does not happen with CH3 or 4

This non linearity does not affect CH3 or 4 so I think the vertical amp U600 is fine, and swapping with a good spare I have did not improve it. I'm beginning to suspect the channel switcher IC, U400 ... do the symtoms sound typical?

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