Hi Jos¨¦,
If you change the frequency from 1KHz to 50 Hz how change the screen?
It seems also that it is a blanking trouble for retrace/stop sweep.
Best regards
Alain
Nota: I didn't resist to find a small vertical frame Philips Scope GM5600, 2 days after my first answer to this post....
Sold as working...I remembered it was heavy....yes, from the rear.
Spot near ok ( brightness adjustment range not important (*2 and no extinction), focus no adjustment, X deviation ok, Y deviation nothing, time base no sweep....(spot on the left)
A view :
