Mac SE CRT is way too bright!

[indigo_k]

Hey, gang - one of the Mac SE's I purchased this summer has a problem with the CRT, where the brightness has to be turned down all the way in order to not have these diagonal lines all over the place. I haven't adjusted any of the potentiometers on the side of the analog board, but I might have bumped something inside when I was checking the battery to accidentally make this happen. What should I be looking at to fix this?

EDIT: I also may have bumped something when discharging the CRT - this is a new process for me

 

[Nixontheknight]

Hey, gang - one of the Mac SE's I purchased this summer has a problem with the CRT, where the brightness has to be turned down all the way in order to not have these diagonal lines all over the place. I haven't adjusted any of the potentiometers on the side of the analog board, but I might have bumped something inside when I was checking the battery to accidentally make this happen. What should I be looking at to fix this?

EDIT: I also may have bumped something when discharging the CRT - this is a new process for me

I think there is a sub brightness potentiometer inside the Mac SE that should make it so you don't have to turn down the brightness to not see lines

 

[indigo_k]

So I popped the troubled Mac SE open and fiddled around more with the brightness potentiometer, and got zero response whatsoever. Without removing the analog board completely, I think I'm going to have a hard time diagnosing the problem, but from what I can see it's possible that resistor R26 might be bad. Also I noticed this Mac has a good amount of screen burn-in - not surprising if it's been running as bright as it is. For some reason I wasn't expecting to need to learn how to fix an analog board on one of these, but I can see now that was naive. Okay! Stuff to learn!

 

[Nixontheknight]

So I popped the troubled Mac SE open and fiddled around more with the brightness potentiometer, and got zero response whatsoever. Without removing the analog board completely, I think I'm going to have a hard time diagnosing the problem, but from what I can see it's possible that resistor R26 might be bad. Also I noticed this Mac has a good amount of screen burn-in - not surprising if it's been running as bright as it is. For some reason I wasn't expecting to need to learn how to fix an analog board on one of these, but I can see now that was naive. Okay! Stuff to learn!
View attachment 14120

yeah it might be bad, see if you can figure out what value the potentiometer is to change it