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Macintosh Color Display: How did I royally screw this up???

LaPorta

Well-known member
So, I did a recap job on the Color Display. It basically went fine and I wasn't having any issues, other than the power jack seemed to be a bit loose. So, I pulled the board, and touched those up. While I was there, I noticed that the areas holding down the metal shielding to the ground track were flaky and cracking. So, I resoldered those as well. I suppose I touched up another connector or two also. I rechecked them after this...and saw no bridges or anything.

Once I replaced everything...now the thing doesn't work properly at all! Look at this nonsense, it seems like the flyback or something is all over the place. I can't get a good image of what it looks like, so I had to take a video (don't mind the background sound from a show I was watching).

I am so frustrated: what the heck could I possibly have done to screw up this perfectly working screen?? I am just so utterly discouraged right now...

View attachment IMG_3272.MOV
 

Byrd

Well-known member
! Not a nice sight after all your work - I'd be removing the case and gently tapping components, connectors with the end of an (insulated) screwdriver; you might find quickly what the issue is. Also check your anode cap is properly reapplied and the yoke connector.
 

LaPorta

Well-known member
Poking things did absolutely nothing, no easy fix. Pulled the board again, looked for anything I could. Touched up some solder areas, nothing major. Now, I get a relatively clear, stable picture that is totally red, like the blue and green drives are not there. As the monitor warms up, then the picture gets less stable and starts to collapse a bit on itself. At least it isn’t the garbles disaster in the video, but I still am not sure what is going wrong.
 

LaPorta

Well-known member
I guess I need to keep a calm approach and take a step back. I have looked this all over can cannot find what would be the issue. I will take some photos that others can take a look at as well. I am not sure why I would now be getting a fully red picture. I am not sure how I could have knocked the green and blue drives out.
 

Big Ben

Active member
Sounds like a bad solder somewhere. By manipulating the board you may have trigger a problem that was just going to happen anyway.
By replacing the caps, you may need to calibrate the display, I wonder if there is a service manual for this screen but they usually have instructions.
From what I see it looks like the CRT is being overdrive (white lines) there should be a potentiometer that allows to adjust that
Also the unstability maybe related to capacitor characteristics being too different from the original ones?
 

LaPorta

Well-known member
There is. The frustrating thing is that after I replaced the caps, it actually worked fine. It was only when I went to take a second look that I noticed some cracked joints...that was when all this started. Thankfully, after touching up some other areas and actually reducing some solder in other areas I repaired...the screen is relatively stable red. I will need to get a photo of it when I am home.
 

LaPorta

Well-known member
Ok, so...

I have stable video now after touching up some suspect areas. However, everything is still straight red. I fooled around with the cutoffs in the back and discovered that if I try up the red or the green, I get red or green contrast lines like how you would get just white ones if you turned the main cutoff too high (as one would expect). However, fiddling with the blue drive cutoff in the back up or down produces no effect at all. That leads me to believe that, for some reason, the blue drive is out. How/where to find that dedicated circuit and see what is up I have no idea. I also tried it with a different video card to rule out card issues...and I did rule them out.

I am attaching photos of the board from underneath, and one from up top. I also included what the screen looks like when in use.
 

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LaPorta

Well-known member
Anyone able to chime in here? I can't find a darn thing wrong with it from a visual standpoint, and so far the actual components I tested test ok. Just not sure where else to go. I hate thinking I ruined this thing.
 

jajan547

Well-known member
Two things, can you record a video of it running in a dark area with the flyback showing. Secondly I think it could be a color drive issue, Perhaps the small board on the back of the CRT?
 

claanu

Well-known member
Could try cleaning PP1 and other pots with isopropyl / contact cleaner, turn them back and forth. Probably not the issue though.

CL6 in the top right of pic 3 looks odd.

I don't see any flaws in your work. Given the circumstances my instinct says loose cable connection or flaw in the wire itself.
 

LaPorta

Well-known member
I will get the video this afternoon. It is frustrating only beacuse it worked just fine without issue previously!
 

LaPorta

Well-known member
After fiddling around a bit more, I find that I do indeed get red, green, and blue lines when the R-G-B brightness pots are adjusted. So, all three electron guns are working. I wondered then if the signal is not coming in. Could this be from me tugging on the cable too much each time I work on it? All the main cable pins appear to at least have continuity with some of the monitor connector...not that I know which ones it should have. I have tested this with two different video cards that work with other monitors, so that is not the issue. If the signals are missing, and it likely is not a cable connection, what could it be?
 

LaPorta

Well-known member
Not sure if someone might know how to actually scope the different video signals at different points...perhaps that would help?
 
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