Sean Bruno Posted June 28, 2022 Share Posted June 28, 2022 I've started work on a sickly A2M6021 CRT monitor. It seems to be in decent shape (from an elementary school auction) with some analog issues. The vertical retrace seems to not be returning to the very top of screen nor making it to the bottom. I haven't been able to hunt down the schematics or SAMS for this CRT. Does anyone have a copy that they can share? If not, does anyone have a starting point or a hint for this type of failure? (obviously, I'm using all ESD discharge and safety here, I have some training on tubes and high voltage) Quote Link to comment Share on other sites More sharing options...
Sean Bruno Posted June 28, 2022 Author Share Posted June 28, 2022 Based on a random thread from a different forum (https://comp.sys.apple2.narkive.com/99TAxRvv/apple-composite-monitor-iie-help-needed) I inspected R741 and its very discolored. It measures nearly a short now, but I can't really tell from visible inspection what it used to be. Quote Link to comment Share on other sites More sharing options...
H454 Posted June 29, 2022 Share Posted June 29, 2022 This a screen shot from the 8-bitguy vid: It look like its glass with no bands. This is the only service manual I can find with any kind of info: https://archive.org/details/Apple_Service_Technical_Procedures_Apple_II_Family_Volume_Two_1992-03_Apple_PN_072-0229/page/n281/mode/2up?q=R741 Its implying that the IIc color monitor might has the same internals. But no wiring schematic. Let me check my pile of parts to see if anything matches. Quote Link to comment Share on other sites More sharing options...
nick3092 Posted June 29, 2022 Share Posted June 29, 2022 (edited) Unfortunately I have never found any schematics for the various IIe/c color monitors. Making things worse, they used two different chassis, as noted in the tech manual - S series and H series. My guess is Samsung or Hitachi as the manufacturer. I recapped my 6021 back in March. I checked my photos and I see the same. No real marking except a red band. If I can, I'll see if I have a chance to open and check mine. Probably in circuit though, don't think I'll have time to properly desolder one leg and check out (if I have a chance to check at all). So that may not be overly helpful if it's in circuit. Edited June 29, 2022 by nick3092 Quote Link to comment Share on other sites More sharing options...
nick3092 Posted June 29, 2022 Share Posted June 29, 2022 (edited) I just opened my 6021 and measured R741 in circuit. I'm also seeing about 2.3 to 2.5 ohms. As my in circuit reading is the same as yours out of circuit, it's probably safe to say that's it. It wouldn't be easy for me to desolder one leg to check out of circuit without pulling the board anyway. Edited June 29, 2022 by nick3092 Quote Link to comment Share on other sites More sharing options...
Sean Bruno Posted June 29, 2022 Author Share Posted June 29, 2022 11 minutes ago, nick3092 said: I just opened my 6021 and measured R741 in circuit. I'm also seeing about 2.3 to 2.5 ohms. As my in circuit reading is the same as yours out of circuit, it's probably safe to say that's it. It wouldn't be easy for me to desolder one leg to check out of circuit without pulling the board anyway. Thank you for eyeballing it. At least I can move onto trying to do more than just visual diags now. Quote Link to comment Share on other sites More sharing options...
Sean Bruno Posted June 29, 2022 Author Share Posted June 29, 2022 Now to hunt down schematics for the Hitachi family around the NP53C family. Quote Link to comment Share on other sites More sharing options...
H454 Posted June 30, 2022 Share Posted June 30, 2022 If you find anything let us know or post it. Quote Link to comment Share on other sites More sharing options...
Sean Bruno Posted July 2, 2022 Author Share Posted July 2, 2022 Unsurprisingly, Apple and Hitachi have responded that they don't have the schematics for any of this stuff. I've grabbed the ReCap kit from Console5 and am going to try and do different voltage checks. Quote Link to comment Share on other sites More sharing options...
Sean Bruno Posted July 2, 2022 Author Share Posted July 2, 2022 Hmmm ... part of the coil winding appears to be snapped. Is this repairable? Quote Link to comment Share on other sites More sharing options...
Sean Bruno Posted July 4, 2022 Author Share Posted July 4, 2022 Apparently it is. Heh, how silly I didn't see this snapped winding. Thanks to the EE in a TV repair shop in this video that showed me how to trace out the windings in a coil for this kind of issue. Quote Link to comment Share on other sites More sharing options...
666Venger666 Posted September 14, 2022 Share Posted September 14, 2022 That was the issue? I have this EXACT same problem with the exact same monitor. I cant seem to get the monitor all the way open. Im afraid to break something and looking around I found this thread. Did you successfully fix yours? any advice on getting the monitor all the way open? Quote Link to comment Share on other sites More sharing options...
nick3092 Posted September 15, 2022 Share Posted September 15, 2022 He posted a picture of the monitor with Oregon Trail in it, so safe to say he fixed it. One of my monitors was a bit stubborn to open. I open mine with the crt facing down, protecting the screen with some kind of super soft material. I had to apply downward pressure on the back plate with the adjustment knobs while pulling upon the case itself. That backplate is part of the tray and stays with the chassis when the cover is off. Quote Link to comment Share on other sites More sharing options...
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