GW Instek GOS-653G Display Distortion

[Branqazwsx]

I have a GW Instek GOS-653G analog oscilloscope that was sitting in storage for a few years. I went to use it today, when I discovered there was a problem with the display. The upper right of the display is distorting the traces on the screen. It distorts with or without a probe or signal. It might be operator error, because its been so long since I used it. Does anyone have a thought to what the problem might be. See my video for the problem:



User manual: http://www.gwinstek.com/en-global/Download/DownloadFile/DownloadFile/download%23_%2301_Oscilloscope%23_%2304_GOS%23_%2382OS-658G0MG.pdf

[JXL]

Check for magnetic field near the CRT

[retired tech]

Like JXL said,might be a magnetic field(around mu-metal shield),or,I hope not,a dropped deflection plate.An old trick is to use a soldering gun(transformer type),turn it on and bring it close to the shield and gradually move it away from it.A foot or so before turning the gun off should do it.This was called degaussing in the old days.

[001]

similar problem

how can I fix it?

[Gyro]

That's trace rotation - there should be a preset scredriver adjustment pot for it (often front panel, sometimes internal).

P.S. Your scope probe compensation is incorrectly adjusted too.   

EDIT: If it is the same scope as the OP's, according to the manual, it is the the control marked 'Trace Rotation' (5) on the front panel!

[001]

Fixed 

https://www.eevblog.com/forum/beginners/epic-newbie-scope-problem/

[Gyro]

@001: It really, really helps to save peoples time IF YOU DON'T KEEP DOUBLE POSTING QUESTIONS! 

[001]

Ok ok 
Thanx

[oldway]

Mu metal offers small coercive force, nominal core losses and small remanence. For this reason, I don't think it is coming from a magnetic field.
It seems to be a bad CRT.

But you should check first the signals at the vertical and horizontal deflection plates with another oscilloscope to be sure.