Bent trace on a Tek 465 scope

[Mr. Land]

I have a very old Tek 465 scope that I picked up many years ago in a
surplus sale.

It works just fine, but it's always had a small anomaly...

If you center a trace vertically on the screen, the left end of the
trace (about 3/8" worth) bends slightly downward.

If you move the trace up away from vertical center, the bend goes
away, and doesn't occur again all the way to the top.

If you move the trace down instead, the bend also goes away, until you
reach the extreme bottom, when it then bends upward slightly.

This effect happens on either channel, and seems independent of the
vertical gain or sweep frequency.

I'm wondering if this would be indicative of some internal damage to
the display tube, or (hopefully) some defective/drifting internal
component that I might replace.

Thanks for any advice...

 

[Jim Yanik]

I have a very old Tek 465 scope that I picked up many years ago in a
surplus sale.

It works just fine, but it's always had a small anomaly...

If you center a trace vertically on the screen, the left end of the
trace (about 3/8" worth) bends slightly downward.

If you move the trace up away from vertical center, the bend goes
away, and doesn't occur again all the way to the top.

If you move the trace down instead, the bend also goes away, until you
reach the extreme bottom, when it then bends upward slightly.

This effect happens on either channel, and seems independent of the
vertical gain or sweep frequency.

I'm wondering if this would be indicative of some internal damage to
the display tube, or (hopefully) some defective/drifting internal
component that I might replace.

Thanks for any advice...

IF all your power supplies are good;regulating and no excess ripple,then it
sounds like a bad CRT,with internal damage.

if you input a fast rise signal and set the sweep time/div to display 1
edge per division,you may see just how much the geometry is distorted.I've
seen some very bad ones.Time marks were often used for this.

The CRT is spec'd to the center 8 div,BTW.Outside of that,linearity is not
considered.