Color Classic video issues

[shadedream]

So I've been having some video issues with my color classic and I'm trying to track down the exact cause of the problem. When I acquired the machine a ways back everything was fine. It started with some distortion at the top and bottom corners and the display being overly bright and washed out (camera on phone adjusted for the brightness so it's not as washed out in the photo as it appears).

More recently I started noticing some brightness flickering going along with it. In attempting to record a video of the flickering today, the display very briefly blanked/dimmed and all of the distortion / over-brightness was gone. The flickering remained and eventually it happened again and popped back to the distorted video. The distortion is also worse than the above photo now.

Video of it in both states (didn't catch it switching):

https://www.youtube.com/watch?v=O_8bPka1sYM

My assumption is caps on the A/B but I don't know for sure. I have tested two different logic boards (both Performa 575 boards) in it and nothing changed.

Thoughts?

 

[uniserver]

Yeah the caps, they are pretty much toast,  and it could also be one of the many potentiometer's that need to be cleaned and worked.

 

[Elfen]

Yeah, its the caps like Uniserver says. After they are replaced, the analog board needs to adjusted. To clean out potentiometers get what is known as "TV Tuner Cleaner" from your electronics store or "Power Window Switch Cleaner" in the automotive store and zap the potentiometers with the spray a couple of times. Let it dry out. Then turn it on and make the adjustments as needed.

First adjustment - in a dark room, adjust the brightness so there is no grey around the display (like there is on your pic). That will balance out the black as black. Then adjust the contrast until it is sharp (and the dark area is still black); you may need to tweak the brightness after adjusting the contrast.

Then adjust size the screen as per Larry Pina Specs for a B/W Mac. Finally adjust the centering of the display.

 

[shadedream]

Yeah... thats kind of what I'd feared. I'd already sent Uniserver an e-mail about the caps to get an idea assuming that was the issue before the brightness flickering started. Will need to get around to making a tool to discharge the CRT so I can get the analog board out and get the money together to ship it off it seems.

Elfen, have a link to these adjustment specs? not familiar with them. Fortunately when the display pops out of it's distorted mode it's brightness and black levels are correct, though Im sure I'll probably have to do some adjusting. I did get some adjustment tools just recently to troubleshoot it, so good to go there...

 

[Elfen]

Looking at the Classic Mac and SE upgrade and repair secrets, the measurements are:

Height: 4 & 3/4 inches

Width: 7 & 1/6 inches

Center by eye. I use two pieces of string crossing diagonally taped to the bezel, but this can be off too but it is enough to help out a bit.

I forgot to mention, also adjust the focus until it is sharp.