Old Tek 465 with "bent" trace

[klandingham]

Hello,

I have an old Tek 465 scope that I picked up from a local electronics salvage place quite a few years ago.

It has always had a problem with the trace, and I'm finally getting around to trying to fix it, or at least find out the cause.

The issue is that regardless of the input, the right side of the trace "bends down", i.e., looking at a no-signal trace from left to right, the beam is flat as expected until about the last 1/3 of the horizontal screen width, then smoothly curves down towards the bottom of the scope.

Other than this oddity, the trace seems healthy: plenty of brightness, focuses well, all the controls seem to work as expected, and waveforms seem to display normally (other than the right-side bending).

I know very little about this scope, and was wondering if this could be an electronics problem, or some kind of deflection plate damage inside the tube (do these use deflection plates?).

Appreciate any ideas, thanks.

[wasedadoc]

Yes they do use deflection plates.  Electrostatic deflection.

It is more than 40 years since i last briefly tried a 465 and decided to stick with a 453A.  Does it have a horizontal shift control?  If yes and you move the trace horizontally does the bend also move or does it stay in the same place on the tube face?

[tggzzz]

Welcome to the forum.

There are several possibilities, ranging from poor PSU to trimpots/trimcaps to damaged CRT.

A picture is always useful in such cases.

How the "distortion" changes as the controls change can be very useful information, e.g. changes with

• sweep speed, including *10 magnification and main/delayed sweep
• moving a horizontal trace from the bottom of the screen to the top of the screen
• observing the cal out signal, and seeing how the trace varies across the screen

and anything else you might notice.

You will probably benefit by downloading the operation and service manual from any of the usual places (e.g. tekwiki w140.com). Best if you find one that matches your serial number.

If there's no obvious CRT damage, the first thing to check is always the PSU rails for DC value and AC ripple. After they are OK, you can move onto looking at the maintenance adjustments in the manual.

[DavidAlfa]

Isn't the trace rotation potentiometer working?
Or it only straightens it partially?
I know it's a 475 picture but should be pretty much the same.

[p.larner]

mine did same but on both traces,it was a psu cap high esr.