How to identify screen burn or blotchy problem in corners

[Chas10_4]

Just bought a graded Sony 36FS70 and find there are dark shaded blotches n all 4 corners, when a white or light coloured backgrouns is displayed. Not visible when darker pictures are on screen.

They are not linear as would be the case if it had been left in 4:3 mode with that type of screen burn.

Is this possibly a setup problem, or is this maybe why the set is graded and sold refurbished?

Any thoughts.

[gringottsdirect]

It probably just needs a thorough de-gaussing after being moved.
This particular tv has a stronger than usual internal de-gausser but a manual wave in front of the tube by a service engineer or by doing it yourself if the dealer will lend you one, with instructions for use.
Have you any large speakers close by the tv ?

I would be surprised if it is anything more serious.

[Chas10_4]

Thanks for the tip, i'll try to borrow one. I was led to believe that Sony TV's degaus on every startup.

The only speakers there are the internal ones left and right.

[LV426]

All CRT TVs do degauss on startup. However, with large CRTs this dark shading can be a permanent feature. It's a misalignment issue in the tube. One of the not-so-perfect attributes of CRTs. It can be cured by a competent engineer by attaching some tiny permanent magnets to the neck of the tube.

[Chas10_4]

Thanks Nigel that gives me something to discuss with the shop.