68kMLA Classic Interface
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| Macintosh Plus. Very vertical image at startup | |
| Posted by: ferol on 2022-06-15 14:47:20 Macintosh Plus .very vertical image at startup Hi everyone from Spain, Recently the capacitors have been replaced on the analog board of my Macintosh Plus since there were problems with electrical tension. Now, when the computer starts, it shows a very stretched image vertically, after a minute, the image is normal. Do you know what could be the problem? attached video Thanks a lot. | |
| Posted by: Byrd on 2022-06-15 22:37:14 Hi ferol, I'd guess dry solder joints on the analogue board need reflowing - do this around the CRT adjustment pots, and cable going from the yoke to the analogue board connector - you might see some scorched solder joints here, double check the cable itself too for arcing/corrosion. | |
| Posted by: ferol on 2022-06-16 05:48:29 Thank you very much for your quick response. the welds were checked. It has also been tried with another cable. the cause of the defect must be something else, I suppose. Could this be a flyback problem? Because as it heats up the image stabilizes. thank | |
| Posted by: cheesestraws on 2022-06-16 07:09:10 Go back and check them again. Especially check things like solder joints around the image height potentiometer. Those boards are notorious for cooking themselves, which breaks initially good solder joints. Do not think this is just the solder joints you made. I would very much not expect it to be the flyback. | |
| Posted by: ferol on 2022-06-16 10:15:57 Thank you very much Cheesestraws, We have followed your instructions, but unfortunately there are no changes. | |
| Posted by: desertrout on 2022-06-16 14:23:52 Welcome! Some thoughts:
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| Posted by: ferol on 2022-06-17 07:18:26 Dear Desertrout Thanks a lot. I answer your questions. the defect continues. Did you replace C1? If so, what did you use? ----3,9mfd 35v Check R1, should be 220 OHms------------------Done Inspect / reflow pin 4 of J1 (the top one) --- does the connector look burned?--Done and NO inspect / clean the yoke connector pins and socket (at the back of the tube) --Done | |
| Posted by: desertrout on 2022-06-17 09:09:23 Thanks for verifying. I'm assuming that the width adjustment pot is working correctly (L2 - sometimes it needs a cleaning), so maybe check /reflow the solder joints on the flyback, specifically pin 2 (for the horizontal sweep)... EDIT: rewatching the video, this actually looks like something on the vertical sweep, not horizontal as I was thinking... so perhaps you should be focusing in that section of the circuit, starting with a good test and clean of R55:  | |
| Posted by: ferol on 2022-06-17 10:38:27 I will get the components that I miss to change those that are in the list of your diagram. To be continued. Thanks | |
| Posted by: ferol on 2022-06-18 09:40:28 I changed all components in the list (and more): L2,R55, CR2 to CR7, CR8, CR15, Q1,Q2, Q4 and Q5 from a working analog board. They are no changes..... | |
| Posted by: desertrout on 2022-06-18 12:38:10 OK... Before swapping in all these components, did you try the other analog board in this machine? | |
| Posted by: ferol on 2022-06-18 12:46:05 yes, like I said, it's a working analog card, and the Mac Plus worked perfectly with this card. | |
| Posted by: desertrout on 2022-06-20 07:32:56 My apologies - it wasn't clear to me that you had tested the tube with the other analog board. Well, I guess try the flyback then just to rule it out. If that doesn't solve it, my first thought is a voltage regulation issue that might be discerned by measuring voltage at the floppy port and the pins on J1 during boot up and comparing that to the working board. That might reveal a pathway to troubleshoot (instead of just swapping in parts randomly). | |
| Posted by: ferol on 2022-06-20 10:27:41 It is I who apologize, sometimes my answers are a little evasive, not precise enough and I thank you for your attention to my problem. What type of voltage should I find on J1? How do I adjust my multimeter? What cable should I check? I cannot change the FlyBack: that of my analog card is not the same model as the card which does not work well. | |
| Posted by: ferol on 2022-06-21 10:56:23 Comparatively, between a Plus working and the Plus with problems, there are no differences in the voltage of the J1 cables: Red and blue = 5.10 V, Yellow and green = 0.12V from power on to 10mn of use. | |
| Posted by: ferol on 2022-06-24 04:57:17 Any suggestion? the problem remains the same. 🙁 | |
| Posted by: keelus on 2023-02-02 12:36:39 Hello, did you managed to fix it? I'm having a similar issue, but instead of stretched, it's compressed. | |
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