My A2M2010P is showing a bright green spot on powerdown for a couple of seconds, so it seems that the brightness circuit is still powered after power off instead of quickly closing and blocking the electrons streaming from the still hot gun.
I am thinking to recap it (I checked things and they seem intact, but I need to test the ESR of the caps). Any thoughts if that may fix the issue, or is there a known issue with the spot-killer circuit in this model? I don't want to burn the phosphor in the center of the screen every time it powers down.
The issue was recently discussed here.
On the CRT FAQ, some tidbits of advice about how a circuit could prevent the afterglow aren't hugely helpful. What happens if you turn down the brightness and/or contrast before killing the power, and is it any different if the input video signal is present or absent?
Thank you for your reply. I appreciate it.
Thank you for the other discussion. I didn't find it as my search had mistakenly been too narrow to the A2M2010. I read through your detailed response there, and I will do a search for circuit schematics of this board.
To answer your questions directly: If I turn the brightness completely down (no text visible) and turn off the monitor, I still get the spot. If I turn off the A2 (or disconnect the composite cable) and turn off the monitor, I still get the spot. It is quite bright and lasts for ~2 s as it fades out. Attached are two images. First is the normal operating conditions, the second is the spot (NOTE: the camera has blurred the spot: it is much smaller and brighter).
Normal Operation
spot
Amendment to the previous: I was able to download the SAMS documentation for the A2m2010. I had confused that the dial on the side of the monitor is brightness, but it is contrast and there is a brightness on the rear. I will retest by turning down brightness to zero and turning it off. It will have to wait a day or two until I am back in the lab.