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AppleColor High-Resolution RGB Display Diagnosis and Repair
Posted by: jessenator on 2019-08-30 12:36:21 After bending my brain searching for any leads, I decided to post a thread about this specifically. I'm wondering if anyone has taken to repairing older CRT displays and if it's feasible. My ACHRRGBD is, like all CRTs of this vintage, really old and starting to shift color a bit and I wonder if something like a recap would help bring it back. I'll post more photos later tonight, but these are the two I have now. I'll also be sure to get a decent WB from my camera so the color drift is more apparent. There's no real apparent burn in anywhere, but a color shift to green, and it bleeds off the main display area as well. Again, if it's not a real feasible repair, then tell me 🙂 I'll live I guess. It's most noticeable on the black areas so here's an AfterDark shot: ignore the vertical lines on this one (different/motherboard related issue on the computer side): Thanks
Posted by: jessenator on 2019-09-01 19:21:03 Better photos of what I'm talking about. Also, be sure to view it 100% (1:1) otherwise there'll be crazy moire. there is no moire at 1:1 better in-focus:
Posted by: bibilit on 2019-09-02 06:07:11 Never worked on those before but without having a look at the inside, it will be hard to troubleshoot. Capacitors can be an issue (i have seen many leakers before)
Posted by: jessenator on 2019-09-02 08:08:45 Thanks for the reply. I'm guessing it's this board I need to get a better look at? It appears to be AB anyway.
Posted by: jessenator on 2019-09-02 15:35:47 56k warning I looked and there didn't appear to be any leaks on the analog board, so I pried up a metal shield on the back of the CRT to see if there were any adjustment trimmers and there were! I put on some thick rubber gloves, left the plastic cover off and plugged it all in to adjust it live. I think it I got it pretty close: I found a trim called G-DRV or something like that and dialed it in till it looked right to my eyes: Didn't have a calibration image handy on my 4400, so I eyeballed it as far as scaling and position.
Posted by: olePigeon on 2019-09-02 17:16:21 Having worked on some arcade CRTs recently, stuff like that can usually be remedied by adjusting all the trim pots. If you get yourself a set of CRT/TV adjustment tools and a mirror, you can adjust it until it's perfectly aligned. You can probably google for a Test Pattern or Alignment Pattern picture to put up on the screen. Make sure it's perfectly aligned.
Posted by: jessenator on 2019-09-04 09:29:53 Made this one adapted from a Trinitron pattern: and the actual test image (or as close as I could tell):
Posted by: olePigeon on 2019-09-06 08:30:27 If only I could figure out which part is making the high-pitched sound that gives me a migraine, I could maybe hot-glue the component in hopes of keeping it from vibrating.
Posted by: jessenator on 2019-09-06 08:38:10 If only I could figure out which part is making the high-pitched sound that gives me a migraine, I could maybe hot-glue the component in hopes of keeping it from vibrating. Is it all the time or just when the screen is mostly white or very light in display? Our last CRT television would make an awful screech that only I could hear (and the rest of my family thought I was crazy) when the screen when full white. Mine thankfully doesn't do that, or at least I haven't noticed it over the sound of my 4400's fan. I wonder what part would even oscillate like that…
Posted by: olePigeon on 2019-09-06 10:15:39 Just simply when it's on. The pitch might fluctuate depending on what's on the screen, but it's there. And, yes, I'm also in the camp where I can tell when a CRT TV is turned on anywhere in the vicinity.
Posted by: CVKealey on 2019-09-06 10:51:09 It's been a LOOOOONG time since I messed with CRTs or tube TVs, but the noise you're referring to sounds like the flyback transformer. Usually the noise is accompanied by a flicker or other visible distortion, but not always. Way back in the day, I had a client with a brand new (at the time) bondi iMac where they complained of this type of noise. In that case, there weren't any visible cues, and I couldn't hear anything peculiar, although the client could (she was an elderly librarian, so probably much more attuned to hearing noise than I was). In any event, Apple sent a replacement and had us ship back the "bad" one. In their investigation (back when they actually did that) they found that it was a defective transformer.
Posted by: ktkm on 2019-09-07 04:25:05 I love that monitor, and I just recently did a re-cap to one of min (a lot of capacitors the boards combined!). And it really helped to improve the convergence, and the clicking sound it made. The most corroded caps were on the video color board (B-board). There are still some convergence issues in the corners, but after reading up on Sony PVM tubes, I have decided to get a hold on some convergence strips. Great test-pattern by the way! Here are some of the ones I made, if I where to start fiddling with yoke rings.
Posted by: jessenator on 2019-09-07 11:43:40 Yeah, those boards wouldn't be fun to redo! Thankfully, (even though my photos don't show it well) it's still fairly crisp. I'm way too chicken to mess with the more intricate aspects, so hats off to you!
Posted by: techknight on 2019-09-19 11:54:21 the noise is indeed caused by the flyback transformer, more specifically, the ferrite core is loose. it actually vibrates and creates the audible tone. has to be shimmed out and siliconed/sealed to prevent it from resonating.
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