cofford Posted October 12, 2020 Report Share Posted October 12, 2020 (edited) Greetings fellow 68kMLAers! I have a Mac Classic that has had a bit of a screen wiggle during network activity and other power draws, so I went through the analog board and replaced (almost) all of the caps. I've previously replaced the logic board caps as well. Well...after doing that, the screen wiggle is still there, and the top of the screen is now "folded over", like shown in the photo. Has anyone seen anything like this? Any ideas where to start? Thanks, Casey Edited October 12, 2020 by cofford Quote Link to post Share on other sites
JustG Posted October 12, 2020 Report Share Posted October 12, 2020 Hey Casey, Have you checked the voltages? It looks like the screen could use some vertical and horizontal adjustment too. Quote Link to post Share on other sites
cofford Posted October 12, 2020 Author Report Share Posted October 12, 2020 (edited) Yes. 5 and 12v look good. Adjusting vert and horizontal works as it should but doesn't get rid of the folded-over menu area...Reducing the overall vertical area does eventually get rid of it, but only when the area of the screen which is upside-down in the pic above is not used. Edited October 12, 2020 by cofford Quote Link to post Share on other sites
68kMLA Supporter elemenoh Posted October 24, 2020 68kMLA Supporter Report Share Posted October 24, 2020 I had a lot of wobble on one after recapping. It was resolved by replacing the 1N4148 diodes at DP3 and DP4. Quote Link to post Share on other sites
cofford Posted November 20, 2020 Author Report Share Posted November 20, 2020 So I checked the voltages again, and after recapping my 5V and 12V lines were low. Adjusted them properly and the screen wiggle is gone. Unfortunately, the "folded over" section of the screen is still there, and I haven't found any troubleshooting guide that mentions a problem like this. Are there any CRT gurus out there who have seen something like this before? I've tried the rear panel screen adjustment pots/coils without success. Regardless of adjustment, the upper limit of the screen will not go above the "fold" line. Quote Link to post Share on other sites
techknight Posted November 23, 2020 Report Share Posted November 23, 2020 This is known as vertical fold-over and 9 times out of 10 its most certainly caused by a bad capacitor in the vertical output stage. If you recapped this already, you need to go back and double-check your work. a cap was either missed, wrong value installed, a solder bridge, backwards, etc.... The vertical output IC could be damaged as well, but its rare. Quote Link to post Share on other sites
cofford Posted November 23, 2020 Author Report Share Posted November 23, 2020 Thanks, I'll give it a good once-over. Quote Link to post Share on other sites
cofford Posted January 26 Author Report Share Posted January 26 I finally got around to fixing this. Found that I had put a 1 uf cap in the CF1 spot. Swapped in a 47 uf and things are PERFECT. Woohoo! Quote Link to post Share on other sites
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