Oscilloscope not focusing (Telequipment DM63)
Usually after 5-10 minutes to warm up, I have a sharp trace on a dark screen, but recently it has stopped focusing correctly. The screen now stays fully illuminated indefinately, and the dot is stuck as a 1/4 by 1/8 rectangle. The intensity and astig controls appear to be working correctly, but the focus does not appear to be doing anything.
I've found a couple of old threads on other forums suggesting that the issue is likely to be a damaged resistor between the power supply and the focus control, or noise from the power supply itself.
Thanks in advance for any ideas or suggestions.